The Biggest Loser Diet – Explained!

This week, splashed all over the New York Times, was an article about a paper written by Kevin Hall, a senior researcher at the National Institute for Health. It was published in Obesity and titled “Persistent metabolic adaptation 6 years after ‘The Biggest Loser competition“.  This generated a lot of hand-wringing about the futility of weight loss. The study, along with another study presented by Kevin Hall seemed to generate more anxiety about the insulin hypothesis being dead. Of course, both these studies fit in perfectly with the hormonal view of obesity and reinforces once again the futility of following the Caloric Reduction as Primary approach. You could review my 50ish part series on Hormonal Obesity if you want a more in-depth view. So, let’s dive in an explain the findings of both of Dr. Hall’s excellent papers. His conclusions, well, let’s just say I don’t agree with them. The studies, though were very well done. I’ve written about the Biggest Loser diet previously, but here’s some expanded thoughts.2015-1125-NBCUXD-The-Biggest-Loser-KeyArt-Image-1920x1080-UG

Let’s start with the first paper about the Biggest Loser. Essentially, he followed 14 Biggest Loser contestants. At the end of the show, they had all lost significant amounts of weight following a Eat Less, Move More approach. Contestants eat about 1000 – 1200 calories per day and exercise like mad people. What the study showed is that basal metabolism drops like a piano out of the Empire State building. It plummets. They are burning about 800 calories less per day than previously. This had been known for a long time. However, it was always hoped that the body would eventually recover and go back to its original metabolic rate. But unfortunately no, the metabolic rate does not recover even 6 years later.

In other words, if you reduce your ‘Calories In’, your ‘Calories Out’ will automatically drop. This makes sense. If your body normally eats 2000 calories per day and burns 2000, then what happens when you only eat 1200 calories? Let’s use the Socratic method and ask a related question. If you normally earn $100,000 per year and spend $100,000, what happens when your income drops to $50,000? Well, you are not stupid and don’t want to end up in debtor’s jail, so your spending drops to $50,000. Well, our body is not stupid either. If we are eating 1200 calories, we automatically adjust by burning 1200 calories. The body does not want to die, and neither do I. Why would we assume the body still burns 2000 calories? It’s just not that stupid.WHS-3

So, while we all obsess about reducing ‘Calories In’, it is virtually irrelevant for long term weight loss. It’s only ‘Calories Out’ that is important. If you can keep ‘Calories Out’ high, then you have a chance to lose weight. But Caloric Reduction as Primary (neatly abbreviated as CRaP), absolutely will not do it for you. This method is guaranteed to fail. This weight loss method, in the literature, has a 99% failure rate. In this study, 13 of 14 Biggest Loser contestants failed – a 93% failure rate. Pretty much expected

The Women’s Health Initiative study of 50,000 women proved this in 2006. Those women reduced their caloric intake by 350 or so calories per day. They expected to lose upwards of 30 pounds per year. Over 7 years, they lost …. 0.25 pounds! That’s like the weight of a good sized bowel moment, for goodness sake. Hmm. 7 years of Eat Less, Move More dieting or have a good BM? Same diff… This study definitively refuted the Calories In, Calories Out model, but didn’t fit pre-conceived notions, so it is routinely ignored.

That reducing calories causes basal metabolism to plummet was already proven long ago in the 1950s by nutritional history’s favorite whipping boy, Dr. Ancel Key. His famous Minnesota Starvation Study was not actually a study about starvation. Subjects were put on roughly 1500 calories per day diet. This represented about a 30% reduction from their previous diet. They were also forced to walk about 22 miles per week. So, this was a Biggest Loser approach – Eat Less, Move More on steroids. What happened to their basal metabolism? They ate about 30% less, and their basal metabolism dropped about 30%. They felt cold, tired, hungry. As they ate, all their weight came right back.

This is what is sometimes termed ‘starvation mode’. This is what people imagine happens as their body starts to shut down in order to conserve energy. Basal metabolism (Calories Out) falls and you feel like crap. As you eat less, your body burns less calories, so that eventually weight loss plateaus. Then you feel like crap, so decide to eat a bit more (your hunger hormones are also rising like a spire), but not as much as you used to. But, your ‘Calories Out’ is so low that you get weight regain. Sound familiar? Happens to every dieter out there. What’s unfair, is that their friends and family silently blame the victim of having ‘fallen off the wagon’, or not having enough will power. Actually, the dietary advice – Eat Less, Move More is guaranteed to fail. So don’t blame the victim when they actually do fail.sun around earth

So the fact that Caloric Reduction as Primary leads to a decrease in metabolic rate is not exactly news. This has been proven for the last, oh, 65 years or so. But we’ve just chosen to ignore this inconvenient fact because our nutritional authorities, like Kevin Hall, keep bleating that you just need to cut calories. So, when it doesn’t work, they think it’s news. Slow news day, I guess. I mean, what’s next for the NY Times front page – Breaking News – New study proves the sun doesn’t revolve around the earth!

To me, what is stunning is how senior researchers and physicians can claim to be ‘stunned’ at these results. They are exactly what I expected them to be. This has been a consistent finding for the last half century.

So here’s what we’ve learned so far.

  1. Cutting calories puts you into starvation mode.
  2. The key to losing weight in the long term is maintaining basal metabolism, or keeping ‘Calories Out’ high.Metabolism PostBypass

We need to keep basal metabolism high. How? What doesn’t put you into starvation mode? Actual starvation! We see metabolism sparing effect with studies of fasting and bariatric surgery.

What happens with bariatric surgery? This is also called stomach stapling. Because the stomach is the size of a walnut, people cannot eat. Their caloric intakes falls very close to zero. Fasting is the same except it is voluntary reduction of calories towards zero. What happens to basal metabolism? It is maintained! One of the Biggest Loser contestants in fact, did have bariatric surgery. What’s telling is that his metabolic rate started to go back up! Rudy Pauls had regained 80% of his weight before he got bariatric surgery. Then, his metabolism rate went up, whereas almost all the other competitors continued down.

Let’s think about what is happening here (you may also want to refer to my 26ish post series on fasting). As you fast, there are a number of hormonal changes that do NOT happen with simple caloric reduction. Your body senses that you are getting no food. Growth hormone surges. Noradrenalin surges. Insulin drops. These are so called counter-regulatory hormones that are natural reactions to fasting. They keep blood glucose normal. Growth hormones maintain lean mass. Noradrenalin keeps basal metabolism high.biggest loser clip 3

Studies of bariatric surgery show that metabolism does not drop as you can in the graph above.. Resting energy expenditure (calories out) is maintained despite severely restricted calories. Studies of fasting also show maintained metabolic rates. In 4 days of fasting, basal metabolism did not drop – instead, it is increased by 12%. Exercise capacity (measured by the VO2) is also maintained.Zaunder1

Let’s think about what is happening here. Imagine we are cavemen. It’s winter. We’ve eaten nothing for the past 4 days except for some yellow snow. (ahh dang it…). If our bodies go into ‘starvation mode’, then we would be lethargic, tired, and cold We would have no energy to go out and get food. Every day gets worse. Eventually we die. Nice. Why do we think our bodies are that stupid? I don’t want to die.Macro oxidation

No, instead, what happens is that the body opens up its ample supply of stored food – body fat! Yeah! We keep basal metabolism high, and instead change fuel sources from food, to stored food (or body fat). Now we will have enough energy to go out there and hunt some woolly mammoth and beat up the guy who peed around the cave entrance. There is no ‘starvation mode’ with actual starvation. As long as your body fat stays about 4%, you are fine. But don’t you burn protein? No, here’s what happens according to Dr. Hall’s own study of fasting.

You stop burning sugar (carbohydrates) and switch over to burning fat. Oh, hey, good news – there’s plenty of fat stored here. Burn, baby burn.BLvsRYB2

In fact, there has been a direct comparison of bariatric surgery patients with Biggest Loser contestants. In the graph, you can see that metabolic rate was measured in Biggest Loser contestants (BLC). Their metabolic rate just keeps going down, down, downtown. That’s what the New York Times reported, too. But look at the RYGB (Roux-en-Y bypass or bariatric) group. Their metabolic rate slows and then recovers. And that’s the difference between long term weight loss, and a lifetime of despair.

In a related poster, Hall presents data on the ketogenic diet. He measured fat loss on patients in his metabolic ward. He used either a regular diet or a ketogenic (very low carbohydrate diet). He showed that the ketogenic diet lowered insulin levels, people burned fat (measured by fat oxidation) and people lost more weight. Great. However, his fancy measurements of body fat also showed that the rate of body fat loss slowed down. So he said that this ‘proved’ that there is no metabolic advantage to ketogenic diets.

Nonsense. I have my doubts whether this DXA scan can actually detect the fractions of pounds of fat lost. Anyway, the main point is that people lost weight and were still losing fat. However, what he mentions in passing is far more interesting. He notes that the ketogenic diet did not produce any slowing of the metabolism.

That’s the gold medal, buddy!

Over 25 days or so, there is no slowing of metabolism??? That’s the most important part of long term weight loss! That’s the knife edge between success and failure. The difference between tears of joy and tears of sorrow. In the Biggest Loser, contestants had dropped their basal metabolic rate by 500 calories per day. In the ketogenic diet, they are still burning the same amount – EVEN AS THEY ARE LOSING WEIGHT.

So, let’s recap

  1. Caloric Reduction as Primary strategy puts you into starvation mode.
  2. The key to losing weight in the long term is maintaining basal metabolism, or keeping ‘Calories Out’ high.
  3. Failure rate of Eat Less, Move More is proven to be 99% or so. This remains the diet advice favored by most physicians and dieticians.
  4. Actual starvation (fasting or bariatric surgery) does not put you into starvation mode
  5. Ketogenic diets do not you into starvation mode

95 Responses

  1. You made the NYPost. You are an extremist and fasting takes great willpower. LOL

    “Experts add that more extreme diets have their place as well … as long as you have the willpower to stay on them. Jason Fung, MD, author of “The Obesity Code,” advocates fasting to achieve sustained weight loss. He recommends skipping meals for two non-consecutive 24-hour periods because a sustained fasting period triggers the body to burn off excess fat, which only happens after glucose and glycogen stores have been burned off.”

    • Wenchypoo

      OMG, you’re labeled an extremist by the NYT…now they’ll be putting you on the no-fly list, and monitoring your every move (physcially and in cyberspace). Don’t be surprised if one day you get followed to work by a phalanx of large black SUVs. 🙂

      I’m probably risking my own neck just communicating with you, but I look FORWARD to going a couple of rounds with the feds. I’ll enjoy fasting while they have me in a holding cell.

  2. Victoria West

    Dr Fung, I thought you would be interested in this link on an ancient fasting method call Pigu.

  3. I don’t get what the final takeaway is. What’s the difference between reducing your calories and “actual starvation?”

    • You’re body reacts much differently to “getting a little” as opposed to “getting none.”
      When getting a little it adapts by using less.
      When getting none it maintains normal operations so you can have the energy to go out and get some.
      Over simplified – hope it helped.

      • Does anyone have a biochemical explanation of this? What is actually going on that spares RMR?

        • Patrick

          Your body is getting tons of calories from its own fat stores. I imagine it’s harder to access fat when using calorie restriction vs fasting or low carb diet.

      • Very nice summary.

      • Ross Parlette

        While caloric reduction does what is named, it still is (usually) rich in carbohydrates (maybe not so much sugar, but plenty of “healthy” whole grains) and therefore starch. As mentioned in the article, starch (i.e., poly-poly-glucose) keeps insulin high and fat stored. So the body has no choice but to lower basal metabolism.

        In low carb diet (or actual starvation – no carb), insulin is mostly (entirely) gone, fat is freely available for muscle energy, ketones (fats to liver, making ketones) are available for much of the brain’s needs, and what little glucose needed is either generated from bodily protein, ingested protein, or the small amount of glucose / starch consumed.

        At this point it is appropriate to note that “starvation mode” is misleading, even mendacious.

  4. Am I only thinks what is happening to contestants is obvious from a survival/engineering perspective? If you have sufficient body fat that is available and your body/brain can “observe” the sufficient body fat, the metabolic rate continues at the same rate hoping you are successful in acquiring more food before the fat stores are depleted. The deficit in calories being made up by the stored body fat. If the body fat is at some low safety level /essentially depleted/ or the body/brain cannot “observe” that sufficient fat stores exist, the metabolism is put in thrifty mode/reduced metabolic rate, still hoping against hope one can acquire sufficient food to keep starvation at bay before remaining fat store are depleted. In this state one will probably be miserable but its better than death. The likely cause of the thrifty mode/reduced metabolic rate is something in their diet is preventing access to or preventing the body/brain from “seeing” that sufficient stores of fat exist. As studies show that with fasting and lchf only a minimal metabolic rate reduction occurs; could it be that high glycemic index and/or high glycemic load diet causes unfavorable changes in hormones preventing access to and/or prevent body/brain “observation” of sufficient fat stores? Is that why a lchf diet and fasting seem to work way better for most people? Is it because these approaches allow access and/or the body/brain to “observe” the fat stores? Hoping for some good science to come from this but not holding breath.

    • Ken Row

      Doesn’t a high-glycemic diet trigger high insulin levels which, in turn, prevent the body from using its fat stores?

    • Carol H

      I read recently that leptin is important in signaling the brain when to stop eating. In overweight people, they have a situation similar to insulin, where they have plenty floating around but it can’t get where it needs to go. Leptin in these people has difficulty crossing the blood brain barrier where it needs to do its work, but when you eat LCHF it increases your leptin sensitivity and lets it cross so it can tell your brain when to stop eating. Thus leading to the reduced appetite often seen with LCHF diets.

    • Sure, exactly. You gotta burn the glucose first, or store it using insulin, so it doesn’t kill you. Constantly having to deal with this results in insulin resistance and the pancreas is finally exhausted and metabolic syndrome slips into full-blown T2D. Even though I had lost weight, exercised and ate LCHF, even after a 2-week zero carb period my FBG was over 120. Intermittent fasting (alternate 24-hour periods) over a 2-month period has brought it down below 100, my blood ketones are over 1.0, and I’m never hungry. I have to work to get sufficient calories. Actually. I’m gaining muscle working out about an hour a week. And I’m 68 YO. Fun…. ?

  5. Brilliant post, as usual Dr. Fung. Keep fighting the good fight. We’re winning, one post at a time!!

  6. kaminer

    A study with 14 subjects and no control group has close to no scientific value.
    Drawing drastic conclusions from such a study is biased. You can find 10 studies that say the opposite but the author just cherry-picked this one. Not all studies are created equal fyi.
    On top of that, loosely talking about “metabolic rate” without mentioning the NEAT ( Non-Exercise Activity Thermogenesis ) is missing the whole point.
    That’s pseudo-science in action

    • sten bjorsell

      Obviously you missed the references Dr Fung made to the large studies that showed exactly the same before. Even Ancel Keys arrived at the same, starvation in the form of reduced caloric intake (of standard food, not low carb) reduced metabolism in Minnesota (prisons I guess) even with 22 miles walked per day. And the 50,000 women in women’s health initiative reduced 0.25 kg over years, by reducing calories in with more than 10 % . The result from the 14 person study that ketogenic diet did not reduce metabolism is an important one but not new as a quick search showed it to not be well established, or worth a “gold medal” for spotting it and presenting it, as Dr Fung pointed out !

      That I personally fasted 5 days a week for 3 weeks in a row and then lost 9 kgs that stay off with great energy while doing it and after may be a pure anecdote but fits well into the picture and I am very pleased to feel very good after. Before I had lost 6 kgs with LCHF, but could not move from that plateau for over 3 years until I started the 5 day fasts.
      I thank Dr Fung and since I am “normal” in most other aspects I don’t think I am the odd one out. Yet LCHF combined with Intermittent Fasting is a perfect marriage for me as it means no real transition to start fasting, maybe apart from being extra generous with dietary fats the last meal(s); Transition from dietary to body fat then become seamless, no hunger !
      Adding to that self cleaning autophagy during fasting making my now close to 70 year old body feel and work as if it is 20 years younger means Dr Fungs free website is a pure treasure trove for me and seemingly also many others here!

      • How did you fast please Sten? ie What were you taking in during those 5 days each week? And what did you eat on the other two. Am curious. I’ve done lots of fasting and within around a couple of days the body shuts down with regard to elimination. It’s advisable to eat only raw food after a few days.

        Did you eat raw for 2 days then returned to fasting?

        Thanks for sharing. It’s an interesting article and comment section. 🙂

        • sten bjorsell

          Hi Sarah, thanks for asking!
          During the 5 day fasts I ate nothing and drank water with 1/2 a lemon in 1-2 liter water as soon as I felt that I “needed” anything, and day 4 evening and day 5 from lunch to evening bone broth with plenty of sea salt.
          The first time I did not ramp up with the bone broth and awoke during the night with some stomach pains that went away with boiled lukewarm water. The gradual increase of broth fixed it the other two times.
          After the fasts I resumed eating with a standard -for me – low carb high fat dinner, with a glass of wine. Same Saturday and Sunday except for lunch to be social on one or two of those days, then returned to fasting after Sunday dinner, 3 weeks in a row in total, after which I had to break it to travel. I felt warm most of the time during fasting, actually my common cold feet when going to bed disappeared after first 5 days fast!
          Have just finished a 2 day fast as I got a bit tired this time. Weight has gone form 92 to 82 in total , and target is 75 – 80 so I am getting close, taking “smaller steps” now.

          • Sten,

            Thanks for sharing this information. I hadn’t thought about doing a reverse 5:2, but it seems like it would work very well. I am on day 7 of a bone broth fast and will break it on day 8, but think I will resume next week with a reverse 5:2. The first time I did a 5 day fast, I started to feel weak around day 3 and it never left. Turns out I was coming down with a cold. The second 5 day fast was SO much easier. I’m SO surprised that I don’t feel generally cold and you’re right…my feet are not cold at night as is the norm.

            I am grateful for Dr. Fung and his courage to take a “controversial” stance. Reading through his blog posts has answered so many of my questions about why my blood sugar does what it does. He has given me the strength of conviction to stay the course.

  7. I did caloric restriction and didn’t find any lowering of my basal metabolic rate. I have lost the most weight that way, and I haven’t regained. I think we must be careful to scare people away from ANY type of diet. One approach may not work for one, but may work for another.

    • sten bjorsell

      It also depends on how much fat one eat, as was pointed out above. The more fat in the original diet the less metabolic loss I assume the transition to zero metabolic loss looks like. Since the contestants must have had lots of weight to lose I assume most of them were eating a SAD model, a very high (60%) carb diet. But as you say there are of course also individual differences.

    • I wonder Louise if you’ll be able to say the same thing now 9 months later or even 2 or 5 years from now… If whatever weight you loss during your caloric restriction, will you call it a success or failure if you gain double or triple the weight back in say 4 years?

      The caloric restriction diets fail 99% of the time, either from the get-go or long term because humans simply are not built to restrict calories long term. Body will simply shut down energy and hormones (including sex hormones) to conserve itself.

      It’s not really a case of what works for one may not work for another; all humans are built exactly the same way. There are just varying degrees on how things affect our hormones, whether it be in the short or long term. This is passed on through genes, and also attained through lifelong diet. For example, eating a doughnut does not cause someone’s insulin to drop after 15 min of consumption. In one person their blood sugar may go up only 30 points, but another it may go up 300 points. Point is, it goes up. You can restrict calories in 100,000 people, some will lose weight, some will stay the same, and some will gain. Ultimately though at some point, metabolic rate will fall in all 100,000 of those people at some point. May happen in 1 week, or in may happen in 10 years. That’s just the way that it is, we are all built 100% the same, with varying degrees on how things affect us over time.

  8. One more humble comment if I may – you will expend more energy, surely, if you are overweight, and as you get lighter, you expend less so does that not come into play?

    • Sure it comes into play. When the talk about drop in metabolic rate, they compare it with someone of the same height/weight, not the same person before they lost the weight….

      • Yes, the BL contestant six years on are about where you would expect them to be metabolically, using published equations.

        Much of the talk is based upon Hall’s original study that (dubiously, IMO) used a regression analysis amongst the participants as the basis of predictions, which seemed weird to me at the time as the sample size is tiny and had a massive CV (note to researchers – don’t mix men and women in metabolic studies). In the current study there’s even talk of relocating the original equipment to try and reproduce the measurements.

        If anyone has access to the full data set, or wishes to make a FOI request to get it, perhaps they could compare measured RMR with predictions using accepted equations for each of the participants.

  9. […] What is really shocking and pretty depressing about this is that these contestants’ metabolism remained low after the diet. Lower in fact than needed to maintain their slimmer figures. Now a certain reduction in metabolism would be expected with weight loss ( As we decrease in size we do require less energy to maintain our smaller size) but what happened here is that resting metabolic rate (RMR) decreased to LESS than was expected at the new body weight.Check out Dr Jason Fung’s blog post here for more detail  and here […]

    • I’m in this situation, I lost 110kg (240 lbs ish) a journey I started over 6 years ago, I’ve managed to maintain the weight loss for 4 years, which has been a journey in itself, which lead me to trying various things, including insane levels of cardio but it eventually lead me to LCHF 3 years ago but and it’s a big but, my metabolism is completely broken, something I believe is reinforced by the fact that my body temperature is always low, sometime by as much as 3ºc. Nothing I have done to date has managed to correct it.

      It’s extremely hard to get people to focus on the long term when faced with starting out on a weight loss journey, especially if that loss needs to be mammoth. From my own experience, most expect to fail deep down and therefore are often have the attitude of “I’ll tackle that when I get there” when it comes to weight loss maintenance.

      I wish I had the knowledge that I have now when I started out but we can’t have everything!

      • Hopefully things have gotten better for you since May. If not and you happen to read this, it’s a simple case of just eating more, a lot more. Yes you will gain weight in the short term, but it’s required to rev up the metabolic furnace again. What you did is a common mistake amongst all paleo or LcHF eaters, they usually still unconsciously avoid fat while eating too more protein. This in turn causes an unwanted caloric deficit; this is because Protein is satiating.

        You can consume sugar in the short term, maybe 1-2 weeks but no more than that to kickstart the process (as sugar rapidly increases body temp), but ultimately, the goal is to simply just eat more, a lot more. I’d recommend aiming for minimum 3000-4000 calories daily. Also add lots of salt to food. The feeling you want is to basically walk outside in the winter time in a t-shirt and your hands should still be warm. That means the cellular respiration in your body is a peak efficiency and your burning hot.

  10. Dr. Fung, I’m a little unclear on the difference between calorie restriction and fasting. You say that fasting doesn’t decrease your metabolic rate. Does that mean that you don’t have to fast your whole life to maintain weight loss? If I go from 190 to 170 lbs due to fasting, do I burn a normal amount of calories for my new weight or will my metabolic rate go down?

    • sten bjorsell

      Dr Fung has explained it: When you are young or with no or little metabolic syndrome there is no or low insulin resistance and it is possible to lose weight without losing metabolic rate, because insulin is still low. High insulin means store fat for the baody, not the opposite. The key signal making weight loss a sure fail, unless done right.
      When we are older or have abused ourselves with fast carbs combined with lots of proteins and fats for years, insulin resistance and high insulin is often dominating. If we then reduce food intake drastically, but only to half, and exercise as in biggest loser, our insulin levels are not really changing. Larger food intake reduction is generally required to also reduce insulin, and with no food at all for a few days the blocking insulin will “drop out” and no longer lock up body fat stores.

      With lower food intake we had hoped that the balance of body energy would come from body fat, but the insulin resistance puts up the barrier and the body decides to balance the lower food intake with lower consumption, and reduces metabolism and making us tired instead. Only due to our elevated insulin, kept up by feeding us some food every day.
      Yet, if the food is low carb high fat instead, with low protein, the insulin is not pushed up as much every day, and then even the “biggest loser” will work, with persistent result and even slimmers reunions! Low carbers say that less calories in and more calories out does not work, while the calorie side disagrees. The tough thing is that eat less and run more works, but only for low carbers! That is the real PARADOX! Yet fasting “cuts” it a lot quicker and the combination of low carb with fasting seems to be the real Rolls because the transition to fasting can hardly be made smoother: Same fuel, different source.

  11. Dr. Fung, I was extremely excited to see your explanation here, along with comments about Dr. Hall’s recent research “proving” that insulin doesn’t cause obesity. I’m a keto dieter myself and have seen amazing health transformations and it seems to be the only thing that can rein in an obese person’s appetite. I’m curious more about what you say about gastric bypass though. I have not seen it be a long-term solution for obesity in my practice. I’ve attempted to work with people who had surgery 10 or more years ago and they had gained nearly all their weight loss back, were constantly cold, hungry, etc. all your hallmarks of slowed metabolism. What are your thoughts about this?

    Dr. Jason Fung: The surgical patients always regain their weight because they have not actually learned anything about how to keep the weight off. Once their stomach stretches back to accomodate more food, they go back to their old habits and then regain all their old weight.

  12. Trina Hughes

    Dr.Jason Fung , I was hoping you’d see this “study” and say something about it !! Thank you for all you’ve done to help me understand what is going on with my blood sugar levels and how to actually get my insulin down … Fasting is working amazingly with a ( low carb) lifestyle … I hate saying low carb diet , it’s not really true , I just stopped eating garbage and replaced with vegetables …. I don’t a ton of food , but I’m not hungry all the time like I was before and I have zero cravings anymore …. Thank you again for saving me from a long road of medicine and pain ? sincerely Trina

  13. […] more to it, is drafting his own post now, and in sporting fashion, I’ve emailed links to Jason Fung’s alternative take, as well as a transcript and image of Kevin Hall’s poster to help Mike draft his post with […]

  14. Eleni Jae

    What if, like me, you’ve been on the diet roller-coaster for years – losing and gaining more over and over due to the “wonderful” advice we’ve been given? How does one “fix” their metabolism? I’ve been following the ketogenic diet for 10 months now – and it’s been great- but my calories have to be around 1200 to 1400 per day to lose any weight. Just following the CRaP method. (I love that – so TRUE!) How can I resurrect my metabolism back up to where it should be, rather than having it remain what years of WW dieting created? Is fasting the answer? I don’t want to have to eat this little for so long! Perhaps I’ve just not found the right article on your blog yet…

    • Hi Eleni Jae, if you haven’t read The Obesity Code, it’s probably a little hard to distill the answer because the discussion is spread out over numerous different series of blog posts. To summarize my take on it:

      I think everyone agrees on this (or has to concede this) by now:

      * Your brain has a body weight or body fat target that it seeks to maintain, often called your “set point.”
      * If you undereat and/or exercise like crazy, resulting in weight/fat loss, your body will attempt to return to its target level by (A) using less energy (reduced metabolism) and (B) motivating you to eat more (making you hungry).
      * If you overeat, resulting in weight/fat gain, your body will attempt to return to its target level by (A) using more energy and (B) motivating you to eat less (reducing your appetite).

      So what everyone wants to know is, how to beat the system. I think there is less agreement on that point.

      Insulin and insulin resistance are believed to be key players in maintaining and pushing up your body weight set point. So the first step is to adopt a diet that imposes a smaller insulin load and stop making the problem worse. I’m sure everyone reading this site has done that over the years, one way or another, with more or less success. But that typically is not enough to make a big difference in weight.

      The suggestion to fast is based on the need to balance persistently high levels of insulin caused by insulin resistance (and our 24/7 snacking culture) with extended periods of low insulin. This should gradually improve insulin sensitivity so you produce less and less insulin to clear blood glucose on non-fasting days. A virtuous cycle.

      If your metabolism has fallen by 25%, it suggests your body is fighting to get back to its old body weight/body fat set point. If fasting “works,” you should gradually be able to lower your set point and your brain should compensate by burning more energy. Joining this experiment is free — and you’ll save money on food and gas!

      This was only my third day on what I tell people is the TWD diet: breakfast-lunch-dinner one day — no snacks — then tea-water-dinner the next, which is 23-24 hours of fasting, dinner to dinner. So far, I don’t have any success story to tell, except that it’s getting easier. No headache before dinner today, and burying myself in projects kept my mind off the clock. It’s a start.

    • sten bjorsell

      Dr Jason wrote the answer above: “However, what he mentions in passing is far more interesting. He notes that the ketogenic diet did not produce any slowing of the metabolism.

      That’s the gold medal, buddy!”

      Take out most of the carbs = ketogenic diet = no slow up of metabolism. On your low calorie intake it may work after a while. Starting to fast becomes very easy from a low carb/ketogenic diet as the diet adapts the body to burn fat first, meaning very little hunger. So if the low calorie low carb eating doesn’t work, give it a push with a one or two day water fast and repeat weekly for instance. With IF you can eat more or normal (LC best) when not fasting.

    • Some women like yourself are doing well on JUDDD which is a modified every other day fast eating 25% of your maintenance calories ie 500 cals every second day (your down day). This allows you to eat more the other days (the up day). Most women only count the down day calories and eat ad lib the other days (within reason of course).

    • I’m in exactly the same boat Eleni years of roller coaster traditional dieting then finally I managed to shift the weight, all 240 pounds of it. I’ve maintained the loss for a number of years now but It has left me with what can simply be described as a broken Metabolism, my body temperature is always low, sometimes it’s as low as 34ºc, I had some surgery last year and the recovery room nurses refused to return me to the ward because of my low temperature, despite my protests and attempts to explain it was normal now for me. I am often tired, cold even in Summer!

      I don’t think that insulin is the sole culprit here, I have followed a Low Carb High Fat diet now (whilst maintaining) for well over 2 years and I am strict with it, I am often in Ketosis and would probably be described as Fat Adaptive.

      At the beginning of the year I did a 10 day water fast, out of desperation to fix things really, I’d done shorter traditional fasts often before but nothing that long. It went well and after I saw some promising results, especially with body temperature and energy levels for a couple of weeks after but slowly things have returned to where they were.

      I really hope there is a fix for those of us that may have lost our weight the wrong way!

      • Eleanor

        That is interesting that the fast offered you some respite for a couple of weeks.

        There can be a massive increase in RBC (red blood cell) production during longer fasts — wonder if there is any connection to that phenomenon and your uptick in energy?

        Or was it due to the higher ketones levels that come with prolonged fasting? Peter over at Hyperlipid has an interesting series about improvements in oxygen handling with higher ketones levels, e.g.,

        That you found temporary relief at least suggests that your metabolism could well rev up over time. 🙂

        Have you ever done a trial of zerocarb? I started one recently, almost a month ago, and from the start it felt metabolically different than strict Keto — which was a revelation.

        Boring, as all get out at first, annoyingly so, but after the first week of adjusting now I really, really look forward to each meal even without the spark of variety from sides of plant foods.

        • Thank you Eleanor for taking the time to post this. I’ve been reading some of Kelly’s blog and a lot of her experiences she describes seem really similar to my own in a lot of ways.

    • what does WW mean?

      • Eleni Jae

        Weight Watchers… too much money for their “advice”. 🙁

  15. Are there actual data and graphics that compares insulin levels for 2 groups who lost similar amount of weight with 2 different approaches : typical CICO vs keto/fasting?

    Blood glucose should be similar but I’d like to see the actual difference in insulin levels.

    I see a lot of graphics that compares RMR , and I understand that somehow, keto and fasting maintains RMR, but I fail to see the actual plasma insulin numbers that compares both sides to support the premise that elevated insulin is the reason behind drop in RMR and elevated BSW in a CICO weight loss.

    I love your book by the way!

    • +1. A study of weight maintenance (or loss) that measures energy flows comprehensively and monitors all relevant metabolic variables would be good. Never seen one yet. Have seen studies showing elevated free fatty acids with reduced insulin on low carb but they didn’t measure energy parameters.

  16. I am doing the 5:2 diet but spreading my calories on the “fast days” across lunch and dinner. Would it be more effective to fully fast until dinner and have the 500 calories then?

    • It’s my understanding that the 5:2 diet made popular over the past few years by the like of Dr Moseley and co is not really fasting it’s better described as an intermittent VLCD, you are traditionally dieting through calorie restriction but instead of creating the energy deficit daily, you’re instead doing it 2 days a week, at the end of the 7 days the deficit is the same or similar.

      To truly fast there need to be a “Period” where you are not consuming energy, through eating or drinking. As you’ve said waiting to dinner would be closer to a real 24 hour fast assuming you’ve not eaten since dinner the day before.


    • sten bjorsell

      Since it can take hours to empty liver buffers every time a fast starts, longer spaces must be better. Both for weight loss and autophagy. It is the reason I drink water only if I fast for one or two days. ( 1/2 lemon squeezed in 2 liter water as much as I feel). For 5 day fast I add well (sea-) salted bone broth during the last days to not lose electrolytes.

  17. I echo Elani. I’ve dieted for years, and am cold and tired all the time. Any hope that I might be able to increase my metabolism in the future?

  18. This study is very interesting but perhaps not in the way it is interpreted.

    1/ it is a small group of voluntary very obese patients without any control group. It means that the selection process led to test a special subgroup of patients who are different from the millions of overweight american people. A control group should have add comparison and better understanding. On the other hand they might be cases of obesity where several mechanisms are put together and pushed to the limits which improved the experiment.

    2/ Obviously those patients ate a lot even in a compulsory mode (quantities matter) , they ate a lot of ultra-processed addictive foods (type of food matters).

    3/Real food was in their plate only during the weight loss time (check the menus reported in the article and the stories about processed foods like chips…)

    4/So ultra-processed food + quantity + addiction = obesity

    I am not surprised of their fate after weight loss.

    The question in the study is:

    Does processed food slow the metabolism? My answer is yes!
    Several mechanisms apart the macronutrient content of processed foods lead to a slower metabolism. Xenobiotics, less micronutrients, thermal damage, pro-inflammatory components id est sugars, W6 vegetable oils, trans fats, are some of the factors which come with processed foods and slower metabolism. either by impairing metabolic pathways or central regulation.

    In conclusion one can easily observe that this generation of american people is struck by tremendous obesity rates. It is also the case in Europe and other industrialised countries but to a less degree. Obviously their genomics has not changed in a so short period of time. Two major changes did occur: a sedentary lifestyle and a shift in food.

    There are evidences that a sedentary life style reduces resting metabolism

    There are also evidences that processed food (I mean products) slower metabolism in comparison of whole fresh food not or minimally processed. In my view and according of epidemiological data it would have been clever to test a group with a whole fresh food menu at each meal.
    In the setting described in the NYT the results are not surprising at all.

  19. I mean, WTF? After Gary Taubes and Nina Teicholz, Peter Attia and yes, Jason Fung, WHY IS ANYONE SURPRISED BY THIS? Intermittent fasting and small does of HIIT and intense resistance training WORK! After years of trying caloric restriction and losing/gaining weight over and over, at 68 years of age my body weight has stabilized and I am gaining muscle mass. My blood sugar has dropped and I have moved into mild nutritional ketosis. My idiopathic peripheral neuropathy has improved substantially as well. I have read pretty much everything written on the subject and follow the movers and shakers on the web, and I can say without equivocation that “The Obesity Code” pulls it all together. For me the key seems to be maintaining insulogenic food at around 15% of total calories, using Marty Kendall’s formula, while keeping fiber high and using vinegar liberally. This pretty much means that I follow Dr. Terry Wahls’ Paleo Plus approach, with intermittent fasting. I feel great and I’m not hungry, even on fast days (alternate 24 hours, 6 pm – 6 pm.

  20. Sascha Heid

    Their BMR dropped because they lost a ton of weight.
    Your BMR depends on your weight, nothing else.
    You compare that to a 4-day fast where you maybe lose 4 pounds and mostly water.

    • Hi Sascha, the contestants’ resting metabolic rate (RMR) fell to much less than is considered normal for their new weight.

      “Mean RMR after 6 years was ~500 kcal/day lower than expected based on the measured body composition changes and the increased age of the subjects.” (p6 of the full paper, which you can download in pre-publication form from: )

      That implies that their body weight/body fat “set point” remained high, so RMR was decreased below normal to allow for weight regain.

      Fasting is suggested as a strategy to reduce the body weight/body fat set point so your weight does not rebound after loss.

      • JL check the derivation of the “expected” RMR – I believe it’s using a mini-regression of the participants at baseline and not a generalised large dataset equation.

        After all the average RMR is 1900 and TDEE over 3000 so these are not metabolically broken people.

        • You are right on the money PhilT, and I hope Dr. Fung addresses your point. Calorie reduction, keto., fasting, etc., etc., can all be great strategies for reducing body weight (and selling books), on their own or combined if they can get you to eat less. There is nothing wrong with these people’s metabolisms at the end of their dieting (PERIOD). Their fat loss should be celebrated and at the end of the day, their RMR at 1900 and their TDEE being over 3000 is waaaay higher than the numbers I get when I punch my statistics into an online calculator. If these numbers are correct, they have a lot of calories to work with each day, regardless of their “slowed down metabolism”. I have about 2000 calories a day to work with based on my height and weight at maximum. In fact, their super high metabolisms at the beginning of this study really just illustrates how sick these contestants were to begin with. Side note – fat burns calories too! Anyways, in a culture of plenty, we all just have to get used to the idea that we need a lot less food than “the world” is telling us to eat. That is what is making us fat, not a “broken metabolisms” people.

    • sten bjorsell

      I lost belly fat (=waist measure) permanently with 3x 5 day fasts over 3 weeks (5:2 “reversed”).
      Other results: much improved morning blood sugars, long time skin problems reducing very much, huge amounts of extra energy, feeling warmer, almost vanishing forgetfulness (I am near 70) and more. Weight was 92 before and dropped to 83.
      Hardly 3 kgs of water. If you google IDM intermittent fasting metabolic rate you hit Fasting physiology by Dr Jason, that at least explains why for me.

      • If I understand you correctly, you shed 9kg of scale weight with 15 days of abstinence over a 21 day period? Interesting. Might I ask how long is your maintenance to date and do you recall the amount of belly fat loss (I’m assuming around 10cm or so)?

        • sten bjorsell

          Down at 82 kgs now, May 19th after another 48 hours fast. I lost 7 cm around belly. Target waist is still -11 cm, so 4 more cm to go… Hopefully there by midsummer, moving gently but with complete fasts when fasting. On a side note, I like the warmth I feel when re-feeding after fasting now. As if both food and body fats burn together when ending the fast. The warmth may be a good reason to aim for a lower body weight /insulin resistance target than the “ideal”, creating thereby a slightly increased metabolism that will constantly try to reduce my weight to the new lower target weight/insulin resistance, allowing extra food…..
          Our grandchildren are always a lot hotter than we are, and they have yet a largely undamaged insulin sensitivity, yet of course lots more in play.

  21. Anita Corbett

    To those respondents complaining of low temperature, metabolic lability.
    My experience has been to introduce Lugols Iodine to my water
    On my fasting day I fill a liter bottle with water and initially titrated it up from 1-3 drops
    As a hormonal component of a Metabolic Imbalance I believe our Thyroid balance and regulation has bee damaged and needs support
    Acknowledging that we are all very unique Chemical Soups I could only suggest some research into this for those who may be interested
    Dr Fung you have my admiration and deepest gratitude for sharing your wisdom and knowledge with those who wish to learn and are willing to take responsibility for their own bodies. You may find yourself , as did Ansel Keys, in Accademic Wasteland, but where there is truth, it will out.

  22. Is there anything that the person who has done many caloric restriction diets over many years can do to increase their metabolic rate? Does fasting act to raise metabolic rate long term, or only temporarily? How about switching to a ketogenic diet?

  23. Confused
    I started IF last January. I am pre-diabetic. When I started my morning FBS were 112-125. I was able to get my FBS down to 98-105 during March and April.
    I have lost only 9lbs but I keep trying though that is difficult in menopause. This past week my FBS has rose back to 113, 115, 117 even though I have not changed anything. I am doing 24 hour fast 3-4 times a week. Basically I eat just dinner and only lunch if really hungry which is rare except weekends are free. One thing that is constant is my BS readings at lunch to dinner are still lower than 4 months ago, they did not rise.
    I am wondering if this DP coming back suddenly is a good thing? I have 50lbs to lose so will DP (Dawn Phen) be a normal thing on this journey?
    One more thing that continues to confuse me, where do you draw the line low calorie vs fasting. If I eat dinner every 24 hours and one day I eat 800 calories.

    • sten bjorsell

      Bo, conclusions from own experience: When initially on low carb eating and same for fasting, body is not used to make BG from proteins and fats which explains initial weight loss and good FBS = “low carb honey moon”. But with lots of kgs still to go and being pre-diabetic your liver is likely enlarged and holding a fair amount of glycogen, more than normal. After the honey moon or when a previously high carb fed person has its liver adapted to produce blood sugar from proteins and fats, things change. Dr Jason has explained it roughly like this: When insulin falls in the morning hours due to low carbohydrate intake day before, this gradually reduces our insulin resistance but low insulin also becomes a signal for the liver to release blood glucose. (High insulin means store glucose for the liver, low insulin means the opposite, to the liver…) xx-diabetic-2 means poor signalling so it takes some time to correct the glucose outflow from the liver, and it would also be a large flux from an enlarged liver. I could not find where Dr Jason wrote this, better than above. But it explains very good what you – and I – experienced.
      Search the site just for dawn and it will get you to the complete explanations!

  24. Patricia

    The actual research being done on the ketogenic diet can help explain what is going on.

  25. What insulin level or range should we aim for when doing a blood test? Thanks.

  26. teleusa

    What is reactive hypoglycemia? I do not see any mention of it on your website. Is this also a dietary issue? If so how can one cure this problem?

    • sten bjorsell

      The more fast carbs one eat the higher blood sugar rise, followed by insulin increase, followed by blood sugar fall.
      If the swings are high the end blood sugar can fall well below normal or become “reactive hypoglycemia”.
      By reducing carbs and and low fat foods all the swings above become smaller and on a LCHF diet for instance there is hardly no blood sugar rise, very little insulin rise and zero reactive hypoglycemia follows.

      “Low fat milk” for instance is not present naturally and our systems are not prepared to handle the high concentration of pure sugars (lactose) and growth promoting milk proteins, keeping us well hungry after drinking same amount of low fat milk as natural or full fat milk. That is the reason skimmed milk was used by farmers to fatten pigs. They remained hungry most of the time without the milk fat. And the pig blood sugars most likely went hypoglycemic several times a day, spurring on repeat hunger.

      • teleusa

        Your reply makes sense to me, I was wondering why there was no mention of “reactive hypoglycemia”, which some Doctors claim to be a precursor to Diabetes. I generally eat oatmeal in the morning and about 1-2 hours later I have symptoms of hypoglycemia. On days I eat a 2-egg omelet, I feel okay for 3-4 hours before the symptoms come on. These symptoms come when blood sugar drops rapidly in an hour.

  27. Ignacio

    There’s another blog making similar points to yours, albeit in a more confusing manner:

  28. […] saw last week with the Biggest Loser study that basal metabolism plummets when you lose weight with calorie reduction. As contestants lose weight, they burn a lot less […]

  29. Hi, I’m in uk. Type 2 3yrs 60yrs age on ramipril 10mg and statin 40mg just started fasting 16hrs seem to have higher bg in morn , is this what is called liver dump? And does this improve in time? Thank you and good luck to all.

    • Hi Jan,

      Yes, until your liver is back to normal then you might experience high morning blood sugar because . My husband and I have been doing LCHF + IF for 3 months now and even though his blood sugar is fine during the day and after eating, his fasting blood sugar is normally still in the 105-120 range. (Which when we began was 380, yikes!). So we know we have a ways to go but we also know if we stay the course we’ll get there.

  30. […] eat anything, and you will lose a lot of weight. I read this great article (in Finnish, here is some of the same things in English) about the Biggest Loser hoax and it was also quite eye opening. For couple past years I was […]

  31. sten bjorsell

    In regard of the study “womens health initiative”, I read the abstract that you linked to.
    In it it says:
    “INTERVENTIONS: The intervention included group and individual sessions to promote a decrease in fat intake and increases in vegetable, fruit, and grain consumption and did not include weight loss or caloric restriction goals. The control group received diet-related education materials.”

    You say in text above that the calorie intake was reduced with about 350 calories per day.
    Did you link to wrong study . “Women’s health initiative” is a different study to the one linked to.
    Please advise soonest!

    • Christopher Hamilton

      Sorry to reply to an old post, but I thought this needed addressed. Sten, as a rule never trust the official results of a study like this, the proof of pudding is in the eating, you have to look at the actual data in this case. Note pages 44, 45, and 46 of the published study linked to above (pages 6, 7, and 8 of the PDF available at that link) and you will see hardly any weight loss at all, and none that was statistically significant.

    • Christopher Hamilton

      The specific information you are asking about is on page 5 of the PDF, look at the intervention vs. The control and you’ll see the difference.

  32. This is something else I don’t understand, the notion that BMR would return to where it started from. My understanding, based upon BMR formula is that weight is most definitely considered in the formula. For instance,
    “Mifflin St. Jeor Equation

    For men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5
    For women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161

    “You’ll want to use a BMR as a rough estimate to set your basic needs,” says Dr. Jennifer Sacheck, Ph.D, an associate professor of nutrition at Tufts University and co-author of Thinner This Year. She notes that this won’t vary too much for a male or female of the same age and body weight. Why the emphasis on weight, height, age and gender?

    Weight and height: “The more mass you have, the more fuel you need to sustain larger organs,” notes Dr. Sacheck, explaining why heavier and taller individuals have a higher BMR. When you lose weight, your BMR decreases and you require fewer calories per day. In contrast, when you gain dense, heavier muscle, your BMR will increase.”

    It seems it is that last sentence that doesn’t appear to occur. If this was Dr Fung’s point, then OK, I get it. By that metric one would lose weight at a predictable rate and then the weight loss would increase as the BMR would end it’s descent and start to rise putting the dieter, effectively, at a much larger deficit.

    As your weight dropped, so to would your bmr. In fact, this is the principal mechanism for how MyFitnessPal works. Presumably the others as well. My understanding of the dilemma was that riding your bmr adjusted by Harris-Benedict – 500 (or 1000) would ‘guarantee’ a 1 or 2 pound loss per week. Which, in my case, worked great, right up until it didn’t. At no time did I think once I dropped from 305 to 175 my BMR would go back to 2580 or wherever it started at. I though what would happen is as my weight approached 175 my BMR would reflect a weight of 175 (or whatever it currently was) and I could stay there or continue to adjust for weight loss, i.e. subtract an additional 500 or 1000 cal/day. However, if 175 was where you wanted to park yourself, rather than ‘lose 1|2 lbs per week’ set MFP to ‘maintain’ and your BMR around 1800 is where you should, in theory, expect to be. One could gain back 500 or 1000 cals/day and remain wherever they were when they chose to stop their decent. My understanding is that what happened was the BMR dropped precipitously lower than Mifflin predicted to the extent that that became station keeping and, in fact, it continued to drop such that the contestant start to gain weight uncontrollably. What I did was precisely what Dr Fung said in that my weight loss slowed (like a plane descending into a landing configuration regardless what I did. I panicked as I did not want to predicted uncontrollable weight gain to occur.

    The other thing I don’t understand is. Now I am fasting, something akin to the 24hr fast except I haven’t mastered eating a meal subsecond so I give myself 3-4 hrs to eat dinner and then my fast resumes until the following day. My weight has resumed dropping nicely but I am also on a 700-800 calorie diet. I understand the fast window as a break from a persistently high insulin secretion. However, I do not sense I am fasting long enough to trigger ketosis, merely clean out my liver. I do not understand how this differs from just doing an 800 calorie diet. My Fitness Pall stops lowering calorie budget at 1500/day for men and 1200/day for women. 800 cal/day is about 1/2 that, for men. If I go to the gym and burn 600cal aggressively doing cardio (3 1/2mph for 60 mins at this current weight and I adjust speed up as I lose weight) 1) that becomes a 200 cal/day diet and 2) what happens when I hit a good ‘wheels on tarmac’ weight and transition to maintenance?

    I hope that makes sense.

  33. Where is the confluence between existing medical orthodoxy and what has been discovered in the last however many years by Drs Taylor, Fung, et al? By that I mean, the conventional wisdom was progressive, chronic disease. One might start on pills but inevitably transition to insulin then transition to more insulin then go blind, have feet amputated etc.

    In my case I followed, pretty much, the glide slope Dr Fung showed the graph on, a slowly rising FG then a precipitous change in slope to a really high fasting glucose followed by a supportive A1C of 8.5. As soon as that occurred, I took action and w/i 3 months drove the A1C to 5.8. The Dr was very congratulatory praising my efforts to control my diabetes with diet and exercise. What? I thought I had reversed it. I believe, actually, reversing my diabetes might mean an A1C below 5.7, which means I didn’t quite get there and subsequent A1C of 6.0 meant drift in the wrong direction. And then what? Krispy Kremes for all? One can add back that 500 or 1,000 cal/day and eat sensibly, little to no sugar, no white flour, little to no starchy vegetables? Or does it mean, continue indefinitely with the fasting?

    I did find it curious the verb chosen by Dr Taylor and the New Castle results, reversing not curing. Is that simply a language semantic difference? Does one reverse chicken pox or cure it? Perhaps part of the answer, or part of the question, is related to there being 2 related but different things going on. There is a fully functioning hormonal system with respect to insulin and diabetes. What signifies cured? Is a sub 100 fasting glucose level cured? The last several days mine, upon waking, has been low to mid 90’s with one morning an unexplained 101. Is cured a recurring 3 month A1C of below 5.7 or is 6.0 or 6.1 also cured, and the websites and books have not caught up?

    The other facet is weight. Is this one simpler to claim victory with. Is a BMI in the normal range cured? I’ve seen blog postings claiming BMI was BS. Is a waist size for a man 34″ or below cured? Presumably this would address Dr Mosley’s comment about TOFI.

    A companion question is, what constitutes ‘sick’? Is an A1C greater than 6.0 indicative of sick? I believe the existing medical orthodoxy does not provide for definitions of cured as every A1C below, what, 8(?) constitutes being managed, either well or poorly and everything over 5.6 being classified as diabetic or pre-diabetic. Was my dietitian correct that pre-diabetes is like being a little pregnant?

    I hope that makes sense as well.


  34. […] is available anywhere else. This is precisely what happened on the Biggest Loser as seen in the study featured in the New York Times. This is also precisely what happens during any caloric reduction diet. That is why these diets are […]

  35. […] is available anywhere else. This is precisely what happened on the Biggest Loser as seen in the study featured in the New York Times. This is also precisely what happens during any caloric reduction […]

  36. Barbara Schipper

    Dear Dr Fung,
    I’m the author of the books on the G.I., you may recall my writing you.
    Your surprise reaction to heightened metabolism on a ketogenic diet is a surprise. Let’s remember that protein is composed of complex molecules that the body must work hard to break down, and on a ketogenic regimen when less sugar and more protein is eaten, the body uses energy taken from stored fat (not glucose) to digest the proteins, and that’s how we lose weight.

  37. Barbara Schipper

    Correction – It was Kevin Hall the calorie counter who erred.
    My apologies

  38. Hi Dr. Fung,

    In your article you mentioned that participants who enter ‘starvation mode’ experience symptoms such as feeling cold and fatigued.

    I’ve been reading your blogs and have been intermittently fasting for about a month now. I am a 25 year old healthy male who works out about 5 times a week. My purpose for fasting isn’t necessarily weight loss per se, but rather to maintain visible abdominal muscles, especially during the summer season. Prior to fasting, I dabbled with the paleo/keto diet for a couple months and the results were OK.

    While I’m noticing physical improvements to my physique from fasting, I’m also experiencing cold and fatigue that last about six hours every day before breaking my fast. I typically fast between 7:00PM until 2:00 PM the next day. I eat like an animal during the eating window and I have been working out (intense weight training and cardio) on an empty stomach between 12:00PM to 1:30PM.

    I am wondering what the symptoms of cold and fatigue that I’m experiencing suggest. Does this mean I’m doing something wrong? Is my body entering starvation mode? Is my body not adjusting well to fasting? Please advise. I’m nervous that my metabolism is slowing down by being on this diet. I experienced good results on low carb.


  39. Roger Bird

    I deeply appreciate a heavy duty science researcher who has a sense of humor. They are generally far too anal retentive for me. (:->)

  40. Roger Bird

    So far in my reading of Dr. Jason, I have not noticed him mention that digesting food costs energy, literally. Obviously there is a net gain in energy, otherwise we would all be dead. But it does require energy to chew, swallow, break-down, and assimilate our food. And this energy expenditure is not insignificant. In the reduced calorie state, most of the energy expenditure is going to continue since we still have to do that chew, swallow, break-down, and assimilate. In the fasting state, all of the energy expenditure will be conserved.

    Just this year the Indianapolis 500 winner won because he didn’t stop in the last rounds for gasoline like everyone else but just kept on keeping hoping that he could make it to the finish line. He did, with literally nothing to spare, and the rest is history.

    I have a lot in my “gas tank”. I don’t really need to stop for a fill up. I can make better time if I just use the energy that I already have instead of stopping 3 times a day for an energy input that I really don’t need.

  41. […] is available anywhere else. This is precisely what happened on the Biggest Loser as seen in the study featured in the New York Times. This is also precisely what happens during any caloric reduction diet. That is why these diets are […]

  42. Hello Dr Fung. I saw your videos and read your blog about basal metabolic rate and wondered how you interpret this new study which apparently shows that low metabolic rate is not a predictor of future weight gain:
    Guyenet etc seem to be saying this is significant. Help?

  43. Hi, excellent diet. Do you have a List of foods that we should consume according to this diet? Thanks.

  44. […] and the failings of calorie-based dieting, have a look at Jason Fung’s work, but especially this piece. And if you’re in a scholarly frame of mind, read Dan Lieberman’s evolutionary perspective on […]

  45. […] the long term, these keep going down, and can persist up to 6 years as shown by the studies of the Biggest Loser Contestants. All those contestants lost weight, and their metabolism slowed by 800 calories per day which […]

  46. Congratulations, Dr. Fung. Another fantastic post that always comes to help us.
    Thanks for sharing

  47. Very good diet, huh?! … I liked the post. Congratulations … well informative!
    Strong hug.

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