Circadian Rhythms – Fasting 19

It is sometimes useful to consider things from an evolutionary standpoint. We can look back at early humans and make some general recommendations. Granted, there is little or no proof, but the exercise is still useful and interesting.

There is often great debate about whether we should be eating constantly, or occasionally. For example, Dr. Yoni Freedhoff recommends, in his book, The Diet Fix to eat as soon as you get up and then every 2.5 hours or so during the day. On the other hand, Intermittent Fasting proponents would say that it is quite sufficient to eat once a day or even once every other day. So what’s the truth? First, let me say that there are people who use both systems and do well. But which system makes more sense?

If humans were meant to graze, we'd be cows.
If we were meant to graze, we’d be cows.

Let’s consider our cousins – the omnivorous wild mammals. It is virtually unheard of, in the natural world, to require feeding 3 times per day, every day in order to stay healthy. Most omnivorous large mammals eat considerably less frequently than that. Obligate herbivores, because of the low caloric density of their food, often require constant grazing – think cows and sheep. Grass, for example has very low caloric density. Much of the grass is indigestible and passes through the cow to exit as manure.

Most carnivores, such as lions and wolves will eat only several times per week or even several times per month. Sometimes this is because food is scarce, but even in times of plenty, it’s probably because food is not so easily available. Catching a zebra is much harder than catching a bag of cheetos. This also likely has something to do with caloric density, since most of the animal foods are absorbed by our bodies.

We’ve all seen those TV shows with lions and tigers all around a herd of zebra sleeping away in the hot African sun. Well, those lions were not hungry and therefore did not eat. One meal per week seems to do just fine for them. If a hippo carcass happens to wash up on shore, sure,they’ll eat. So, understand that eating several times per day is not a necessity for omnivores and carnivores. We are not solely driven to eat by nutrient deficiency.

Physical and mental capacity is not impaired by a lion’s week long ‘fast’. If fasting made them sluggish and stupid, well the lion species would  not have survived very long. No, the long interval between meals does not impair them in any significant manner. They ate a large meal – storing much of the calories in their bodies and then are using these stored calories to survive. It’s normal.

Mammals have adaptations that allow them to survive with an intermittent food supply. That is, the body has a way of storing food energy, so that lion can eat once a week. This goes for humans as well. The main way to do this is to store glycogen in the liver (stored sugar) and then to store triglycerides in fat tissue. When you eat, you are putting food energy into your stores. When you fast, you are pulling food energy out. It’s inconceivable that mammals are designed with this amazing system for storing food energy and yet it is still necessary to eat every couple of hours to stay healthy. That’s like building an amazing pool and spa, and then arbitrarily deciding that you can’t get wet after all.

Hunter-gatherer societies, as well as wild animals virtually never got the problems of obesity, diabetes of cardiovascular disease, even during times of plenty. It is estimated that animal foods provided about 2/3 of their calories. So, for all the modern teeth gnashing about meat and saturated fats, it seems that our ancestors had little problems eating them. It should also be noted that many societies ate carbohydrate based diets (eg. Kitavans and Okinawans) and also had no problems with obesity. It seems to be a modern problem, and I suspect that refined grains and sugar plays an overwhelming role here.

Things started to change about 10,000 years ago with the agricultural revolution. Early man started to farm instead of hunt, which led to a greater reliability of food allowing a typical pattern of eating 2-3 times per day. Even with that, there was little obesity until relatively recently (1970’s USA).

So, it is certainly possible to eat meat and have little diabesity. It is also possible to eat carbohydrates and have little diabesity. The problem, (Nutritionism’s Greatest Blunder) is focusing obsessively on macronutrient content (how much fat, how much carbs). It’s the insulin response that matters, not the macronutrient breakdown. The toxicity lies in the processing, not the food. So highly refined and processed grains and sugars, as well as vegetable oils are the problem, not carbs and fats.

Circadian Rhythms

Circadian rhythms are predictable, 24 hour self-sustained changes in behaviours, hormones, glandular activity etc. Most hormones of the body, including growth hormone, cortisol and parathyroid hormone  are secreted in a circadian rhythm. These rhythms have evolved to respond to differences predominantly in ambient light determined by the season and time of day (which governs food availability). These patterns are seen in virtually all animals from flies to humans, and it is estimated that 10% of a given organism’s genes show circadian changes.

The master circadian clock is the suprachiasmatic nucleus (SCN). It is believed that food was relatively scarce in Paleolithic times are predominantly available during daylight hours. This is mostly because humans hunt and eat by day and once the sun went down, well, you just couldn’t see the food in front of your face. Other animals are nocturnal and may very well have circadian rhythms more suited to eating at night, but not humans.BreakfastVDinner1

So, is there a difference between eating during the day and eating at night? Well, the studies are few, but perhaps suggestive. One very interesting study compared the effect of eating a large breakfast versus a large dinner. While there are many association studies, this is one of the few intervention studies done in humans as opposed to mice. Most have favoured eating breakfast, or eating earlier in the day, although most studies have too many confounders to be truly useful.

So what this study did was to randomly assign two groups of overweight women to eating a large breakfast (BF group) or a large dinner (D group). Both ate 1400 calories/day, and the macronutrient composition of each diet was matched – only the timing of the largest meal was changed. While both groups lost weight, the BF group was clearly superior for both weight loss and waist size (important measure of visceral fat) by almost 2.5 times (-8.7 kg vs -3.6 kg).BreakfastVDinner2

So why there such a huge difference in weight gain? Well, this further graph may explain things a bit. The graph shows the insulin response to meals. The BF group had more insulin in the morning while the D group had more at night, as expected. However, by totalling the Area Under the Curve (AUC – graph to the far right) you can see that overall, the dinner group had a much larger rise in insulin. This is fascinating. The same total calories led to more insulin secretion simply based on meal timing.

An earlier, smaller 1992 study had shown much the same thing. In response to the same meal given either early or late in the day, the insulin response was 25-50% greater in the evening.

Weight gain, of course is driven by insulin. So, while the carbohydrates and calories were identical in both groups, the insulin response was not, translating into more weight for the D group. This illustrates the very important point that obesity is a hormonal, not a caloric imbalance. This study has profound implications over meal timing. There is certainly the well known association of night shift work and obesity. However, this may also have to do with the increased cortisol response due to disturbed sleep.

Now, this does not necessarily mean that you must eat a large meal as soon as you wake up. But it means that perhaps eating a large meal in the evening (after the sun goes down) may cause a much larger rise in insulin than eating that same meal during daylight hours. The problem with breakfast is generally that we are in a hurry in the morning and tend to eat very highly refined carbohydrates (toast, cereal, bagels etc) which tend to also stimulate insulin severely. But waiting until noon to have a large lunch as your main meal seems to be a good solution. This also avoids the ‘rushing out the door’ or ‘grabbing a muffin’ sort of response to the exhortation to ‘eat breakfast – it’s the most important meal of the day’.

Folk wisdom, of course, also advises to avoid eating large meals in the evening. The reason offered usually is something along the lines of “If you eat just before bed, you don’t get a chance to burn it off and it will all turn to fat”. Maybe not technically true, but perhaps there is something here. Eating late at night seems to be especially obesogenic.Circadian1

There is also a natural circadian rhythm to hunger. After all, if it was simply due to food intake, we would consistently be hungry in the morning after the long overnight fast. But personal experience and studies confirm that paradoxically, hunger is lowest in the morning. This is ‘paradoxical’ because the morning time meal follows the longest period of the day without food. Breakfast is typically the smallest, not the largest meal of the day. This indicates that there is a circadian rhythm that is independent of the eat/fast cycle.

Ghrelin, the hunger hormone, shows a marked circadian rhythm with a low at 0800. Interestingly, with fasting, ghrelin peaks at day 1-2 and then steadily falls. This aligns perfectly with what is seen clinically, where hunger is the worst problem on fasting day 1-2. Many people on longer fasts report that hunger typically disappears after day 2.GhrelinCircadian

Hunger typically falls to its lowest level at 7:50 am and peaks at 7:50 pm. This applied to almost all foods. Interestingly, vegetables show no circadian rhythm in desire to eat. I don’t really know what this means but I don’t think it’s because vegetables are not delicious.

Understand once again, that these are natural rhythms that are inherent in our genetic makeup. If you take away all external stimuli, these rhythms still persist. What does it mean that hunger is lowest in the morning? One implication is that hunger is not so simple as ‘the longer you don’t eat, the more hungry you’ll be’. No, there are many more subtle inputs and hormonal regulation of hunger plays a key role.

However, the studies are conflicting. NHANES data on evening eating failed to show any association between late eating and weight gain, as might have been predicted. Nevertheless, the possibility that eating during daylight hours results in less insulin secretion must be considered.

So, what’s the practical implication? At 0800 in the morning, our hunger is suppressed actively by our circadian hormonal rhythm. It seems counter-productive to force oneself to eat. What’s the point? Eating does not produce weight loss. Forcing ourselves to eat at a time when we are not hungry is not likely to be a successful strategy.

However, eating late at night also seems to be a poor strategy. Hunger is increased maximally at approximately 7:50 pm at the same time that insulin will be maximally stimulated by foods. This means higher insulin levels for the same amount of food intake. This higher insulin level will naturally drive weight gain. This is the typical pattern of eating in North America, where dinner is the main meal. This is mostly driven, not by health concerns, but by the hours of the working and school day. This also leaves shift workers at a particular disadvantage. They tend to eat larger meals later in the evening, leading to higher insulin.lake_hammock

So the optimal strategy seems to be eating a large meal in the mid-day – sometime between 12:00 and 3:00pm and only a small amount in the evening hours. Interestingly, this is the typical traditional Mediterranean eating pattern. They have traditionally eaten a large lunch, followed by a siesta and then a small, almost snack sized ‘dinner’. While we often think of the Mediterranean diet as healthy due to the foods, the timing of the meals may also play a role.

One final word of advice – We should DEFINITELY all take siestas. Even better, take a siesta by the lake in a hammock.

55 Responses

  1. I live near the Mediterranean coast.
    Until 8 years ago I used to take a big meal at night and never breakfast. I had been a vegetarian for more than 30 years and I was obese (BMI = 37). That year I started doing endurance exercise (daily 3-hour walk). After 18 months my BMI went down to 35. At this stage I decided to follow the “chrono-nutrition” program devised by Dr. Alain Delabos (and colleagues) in France. An aspect which is relevant here is that we consume a heavy breakfast containing all saturated fats, proteins and little carbs. Practically, for instance, 70 g cheese, 10 g butter, one egg and 50 g bread. Then meat and a little carbs plus vegetables for lunch. Fruits and vegetal fat (nuts, avocado…) around 5 pm. Dinner is (fat) sea food and green vegetable, no carbs.
    In one year my BMI went down tp 26. Today it is 28. I am in great shape and I introduced intermittent fasting and HIIT.
    My point is that, as soon as I started this program, I felt very hungry every morning. I get up, do my work-outs every other day and then enjoy the cheese-butter-egg-bread treat! This is the only meal I never miss, even on the days of semi-fasting.
    There is strong evidence (animal studies) that eating staurated fats in the early morning is a good strategy. I have put links and reported my experience on these pages – sorry, in a Mediterranean language! – :

    • Thanks for sharing your experience. I started eating a high protein breakfast about a week ago. It has made a world of difference. I looked up the study referenced above and I think the improvements in the breakfast group are too big to ignore. I hope Dr Fung will take another look. Eat breakfast (high protein) and skip dinner.

  2. Now if we could also change our work schedules to accomodate that nap…but luckily I have retired.

  3. charles grashow

    Dr Fung

    Your co-author Jimmy Moore – at his last DEXA scan – weighed 296 lbs with 43.9% body fat.

    Any comments

    Dr. Jason Fung: Jimmy has struggled with his weight all his life and shares his daily struggles with the wider audience. I applaud his efforts and his openness. I am a physician and it is my mission to help others with their health problems – obesity being one of them. I do not blame him. I do not look down on him.

    You, on the other hand, seem to gain pleasure from other’s misfortunes and struggles. You delight in fat-shaming, and mock his efforts to better himself. There is no question who I would rather associate with, and it most certainly is not you.

    • It is a fact that there are people who go back to ways of life that are unhealthy for them. Even among people who are highly motivated not to, there are those who will backslide into their unhealthy behaviors. The drug and alcohol addiction counselor who starts using again. The gambler who lost her entire family, and worked to regain their confidence, starts with lottery tickets and is back at the casino in months. And the now healthy, slender carb addict, who tells himself that he can handle a little, now, finds out that he can’t.

      One of the saddest truths about an addiction to anything is that some of the people who have helped others the most cannot, seemingly, help themselves.

      Anyone who loses his respect for a medical professional based upon that professional having too much compassion for humanity is someone who needs to get his own priorities in order.

      • Deb Griffith

        I couldn’t have said it better. Although I have lost, am now in my “normal” bmi and weight range, and have helped many friends to begin their weight loss journeys, I still have bingeing problems. I can EASILY sit down with a half gallon of ice cream or a jar of peanut butter and bag of dark chocolate candy and finish it off. It IS an addiction. It NEVER goes away and there is no cure.

        That someone that size even tried and lost 180 lbs to begin with is something to respect, as most of the people I know who are that size (which are most of the men I work with), won’t even consider changing their eating habits. I think men are under more pressure to “eat and drink like a man”, and they believe any kind of restrictive dieting is for women.
        So give the guy a break.

    • I have not met Jimmy Moore, but he is a “fitbit” buddy, and I appreciate his complete openness. Jimmy is a wonderful man who has enriched the lives of those around him by using his primary skill- communication. Jimmy does not have to have a BMI<30 to be an inspiration. We can not walk in Jimmy's shoes.

    • Well said, Dr. Fung!!

    • What is the purpose of this comment made by Charles? Its neither helpful nor associated with the main article…it just highlights someone else’s unfortunate struggles.
      Just as not every shoe in a store will fit every foot, so also not every method will be suitable for every body type…one day he will find a method which fits him

      Awesome response by Dr. Fung!

    • Either there is more to Charles’ comment that was not included or we all, including Dr. Fung, over reacted.

      If you read that one sentence, objectively, it’s actually a valid question. One who’s answer may help enlighten us.

      I’m just sayin’

  4. I have never been hungry in the morning and have rarely had breakfast (only as a novelty on holidays). I am also very rarely hungry at lunch time so have typically skipped that meal too. Come dinner time, around 7pm, I can happily eat a big meal (around 1,000 cal or more). On the occasions that I’ve had breakfast or lunch I tend to eat more and be continuously hungry (and eating) until the next morning (where the overnight fast has broken the hunger spree). When I do a fast which will be around 48 hours once a week (skipping one day’s dinner) I easily manage to get to the dinner time of the second day before eating.
    Since I am about 12 – 15kgs overweight I have to conclude that there may be a lot to be said for more insulin at night. My concern would be that if I eat during daylight I will want to eat all the way to 8pm anyway, and that is likely to increase my insulin response more and longer. I’m over 50 and it might be too late to change my habits to eating earlier anyway.
    Interesting blog anyway.

    • I was almost in the same eating pattern in the days of obesity – 30kg overweight at the age of 58. However, breakfast served in “modern” France is basically jam, honey, sweetened coffee, fruit juice, bred and butter and/or pastries. The chrononutrition program (as per A. Delabos) restored the traditional way which my grand parents had in their farms: cheese, butter, bread, eggs, sausage etc. Plus no sugar at all. It became clear to me that a sugared breakfast would end up with hypoglycemia at the end of the morning, urging to take more carbs. Sweetened coffee (or tea in India) had become my pretext to eat sugar…
      The day I changed my habits, all this craving for food disappeared. Possibly a change in the gut microbiome, possibly a reactivation of some biological clocks, never mind, this is probably different in every person, although about 80% obese persons have succeded in losing weight (and maintaining it) with Delabos’ “chrono” (designed in 1986).
      I don’t want to advertise a method because I noticed that it requires an adaptation to every individual, which implies a good understanding of one’s own processes: at lunch time I eat no more than 100g of red meat, which is 40% less than advocated by Delabos. We need to adapt protein quantity to our lifestyles. However, I wish to stress that the craving for food (by which we naturally feel attracted to sugar/fat combinations) may completely disappear the very day we feed our body with the right quality and quantity of food at the time its biological cycles provide the best assimilation. I have no more taste for sugar in the morning but I do appreciate to eat some chocolate or pasty at tea time. There is no constraint. On the contrary, “chrono” recommends 2 “joker” meals per week, during which we eat and drink everything we dream of. This is the right time for inviting friends for a gastronomic dinner during which they wonder how you managed to lose so much weight being careless about diet ! 😉
      HMGCoA-reductase is an enzyme facilitating the making of “good” cholesterol and it has a peak production in the early morning. This is an incentive for consuming most (if not all) saturated fats at breakfast time. We also take a small quantity of (organic) bread to keep energy until lunch time. The intensity of hunger before each meal tells us whether quantities in the previous meal were correct.
      I admit that enzyme/hormone peaks may not be so acute in every individual. Yet, experiments in chronobiology show that changing eating habits may activate and/or resynchronize biological clocks – modifying our microbiome. (Links to publications may be found at the bottom of my page
      Still, I am aware that these mechanisms may be more complex because many biological cycles are competing with each other; and food is not the only regulation factor. High-intensity exercise and proper hydration are indispensable for the production of Human Growth Hormone which burns fat mots efficiently. (Read Phil Campbell’s “Ready, Set, GO!”, an excellent guide for over-50 humans…)
      Interestingly, I still have the food craving reflex if I see a table full of exciting foods. But the moment I start consuming some, I quickly feel satisfied, and I even feel disgust if I try to take more. This might be an effect of getting rid with leptin resistance.
      The funny side of my diet experience (same for my wife and close relatives) is that we had the impression that we ate “more” (up to satisfaction) because of having 4 meals a day (often skipping dinner, and skipping tea-time and dinner the days we semi-fast). The reality is that this diet is not a low-calorie one. Eating low-calorie meals with wrong contents at the wrong times had made me very fat!

      • Bernard, I think the idea of timing meals is quite interesting and possibly could help some or even many people. If this kind of timing is helpful, then I say keep doing it.

        For me, since I’ve started intermittent fasting, I feel worse if I eat breakfast (and my wife, who has started intermittent fasting with me, says the same). Part of that, too, is how nice it is to get out of the house or get started on your day without having to eat.

        By the way, I know that there is supposed to be a lessening of hunger for longer fasts, but my wife and I did a 5 day fast the first working week of this year, and we both had a very difficult time. I was incredibly hungry the evening of day 4 and it was all I could do to make through day 4 and day 5. I literally could not wait to eat at the end of day 5. I’ve done another 5 day fast previously, and that time I don’t remember as being that bad. However, this five day fast was so difficult, I’m going to limit myself to 3 day fasts or shorter for the near future (since I no longer eat breakfast, I do at least a 16:8 fast daily and sometimes also make that 8 hour eating time shorter).

        • In my obese-vegetarian time I used to have very long fasts – up to 4 weeks! With no result because of the yoyo effect, as you would guess… Today we have two “fasting days” per week. We should call it “semi-fasting” because our day starts with the usual breakfast. At lunch time we take meat as usual, some vegetables and/or salad, but no carbs. Then we stop having solid food till the next morning. We drink as usual (2 liters in the day) and in the evening we take capsules of krill oil.
          I tried to fast longer, for instance skip the next breakfast or more. I did not feel well at all… I felt “deprived”, which is more than hungry. So we remain with this scheme of an 18-hour fast which does not disrupt our “clocks” because the hunger and sleep patterns are very regular. We feel our bodies as well-regulated engines, which makes a huge difference with the disarray in obesity years. 😉
          Last night due to fasting I slept 10 hours instead of the usual 7 hours. In the morning (before breakfast) I had a powerful 20-minute HIIT. Campbell said that having proteins (and no sugar) juste after the HIIT session is best for a proper use of the Human Growth Hormone.
          As I said, there are probably contradictory hormone/enzyme cycles which may explain why there is no perfect eating pattern for everyone. Part of the process may be cultural: we have access to (pasture raw-milk) cheese and excellent bread, all which we take as a treat. It requires no preparation except the burden of putting bread in a toaster to facilitate the melting of butter. When I travel I take a piece of cheese and a bottle of water to have breakfast even in a train.
          In your pattern I am only wondering when (and in what form) you consume saturated fats…

        • The differences between your fasting experience, Bob, and mine very much supports the rule that everyone is different. I’ve done several fasts longer than 4 days. Each time I snack on the evening of the first and second day because of hunger. Then, the rest of the days, as many 8 more days, I have no problem with hunger.

  5. Maybe this is part of the “French Paradox” – coffee for breakfast and the biggest meal of the day at ~1-2 pm.

    • Deb Griffith

      I was thinking that while reading, but thinking the opposite. Wasn’t the saying “French women don’t get fat.”? And I thought ttc ate a lot latter than most Americans. Luckily, my family eats dinner at 4 pm. I have always cooked early so we could have more time before bed to do whatever.

    • My personal opinion is there is no French paradox, because saturated fat (or “high” cholesterol) is not bad for you.

  6. Leaf Eating Carnivore

    @charles grashow @MickiSue:

    The causes of obesity are complex and, to some extent, unique to each individual. I think it’s dangerous to make assumptions and unsupported simplifications. That’s a good deal of what got us into trouble in the first place.

    I think that the following link might illustrate one of the less known possibilities, worth looking at –

    (See the paragraphs immediately following Dr. Ludwigs video.)

    Personally, I hope the best for Mr. Moore. We all have our struggles, and he seems more generous and courageous in the face of his own trials than would be most of the people I have met in my 66 years.

  7. Amen Dr Fung: I call my siesta “Meditation” which is basically in tune with Vipassana meditation practice. I do think there is something in eating at Midday. Whatever you do, do not look for Yoni’s opus on Amazon ;).

  8. For once, this is very unclear. If a serious study shows that large breakfast eaters lose 2.5 more weight, why on earth wouldn’t one advise people to do just that ?

  9. Cortisol is higher in the morning, so it wouldn’t surprise me that lowering in the morning would do more good than lowering it at night when it is already low. +Cortisol –> +Insulin

  10. Catching a zebra is much harder than catching a bag of cheetos.

    That’s the SECRET! All we need to do now is figure out how to animate bags of Cheetos, then teach them to run…then to hide somewhere in the supermarket other than the chip aisle. This will get Cheeto-eaters to walk all over the store with their carts, and then EXERCISE occurs!

    Seriously, though–we need the italicized statement in billboard form. Then we need to dismantle the chip and cookie aisle in every store.

  11. The mean, unkind attacks that folks make sometimes truly amazes and saddens me. In all of Dr. Fung’s blogs and videos he offers a scientific methodology in his views. Jimmy Moore often says “find what works right for you”. Dr. McDougal’s attack, the attack above and others similar to these do nothing beneficial. That said maybe the haters can learn what compassion truly is. I strongly encourage all to watch Dr. Peter Attia’s TED talk. May then the haters will stop the negativity and develop kindness and compassion. Thank you.

  12. The mean, unkind attacks that folks make sometimes truly amazes and saddens me. In all of Dr. Fung’s blogs and videos he offers a scientific methodology in his views. To question Dr. Fung’s posts, which I believe he does as a service (unpaid) is simply wrong. Regarding Jimmy Moore he often says “find what works right for you”. Dr. McDougal’s Jimmy Moore attack, the attack above and others similar to these do nothing beneficial. That said maybe the haters can learn what compassion truly is. I strongly encourage all to watch Dr. Peter Attia’s TED talk. May then the haters will stop the negativity and develop kindness and compassion. Thank you.

  13. Hi Dr Fung,

    Thank you so much for all your post on fasting. They are great. But sorry I don’t follow your conclusion on this one.
    To make it simple I think that hunger is low in the morning because we are not suppose to eat but starting the day being active and hunting for food.
    Circadian higher insulin response/level at night is not bad in contrary as I think it’s there to maximize the food absorption of nutriments following an active day with low food intake. Logic. High insulin level is not always the bad guy.

    Also i think it’s unnatural to have a siesta during the day while we should be full of energy to do stuff (hunt for food). The need to sleep after a big meal make totaly sense if the big meal is at night. The siesta is in fact the beginning of your night sleep.

    Barely no food during the day and huge meal at night is perfectly natural in my opinion.

    • While your statement about how Humans body clocks are properly set for hunting you agree with Dr.Fung on Insulin because the thing this blog is dedicated to is helping people with metabolic issues which means Insulin is the enemy for us so by eating a large meal earlier in the day when less fat will be stored and entering a fasted state when we are more insulin sensitive lets us burn away the days,months,years, or even decades of fat that we have been carrying.

      Thank you Dr.Fung this article went a long way to explaining why my current system where I eat a large meal once a day around Noon has been so beneficial and has removed my worries about if I should switch the timing.

    • I agree. Where is the “like” button? 🙂

    • I agree, I just posted the same thing as you before read comments

  14. Laura Baier

    Hi Dr. fung, I applaud all that you do for us over grassing cows. No matter what the problem, you always have a solution to enable us to go on. Your interest in all is greatly appreciated. Until your blogs that I followed faithfully, I could not lose any weight at all. I am type 2diebetic, on insulin 4times a day, and up until Nov. 7th. The doses kept increasing. On Nov. 14th. I weighed 206lbs. On Jan.14th. I weigh 184lbs. by eating one meal a day, that being dinner. I fast the first two meals, only by following your tutorials and have no problems. The weight comes off easily and I feel great. Except the other day I awoke in the night and thought my toe was going to blow off my foot. My Doc. said stop your insanity weight loss and all will correct itself. The problem is that I will not stop my insane weight loss, but I’m trying to find a solution to this horrible pain not in my ass but in my foot. Again I must turn to you for your great knowledge in matters. Thank you for your patience Laura Baier

  15. I thought Laurent’s comment made a lot of sense and this pattern works best for me on intermittent fasting as far as comfort goes. If I try the morning or lunchtime large meal, I find myself wanting to snack ALL evening! As a side note, the coyotes I can observe from my house hunt in the evening or at night. In the morning they play and they sleep in the afternoon. They do not hunt every night but when they do, it is often all night long hunting small rodents.
    Dr. Fung and Jimmy Moore…two really great guys that work hard for all of us battling different forms of metabolic syndrome!

  16. As a T1D and an intermittent faster, I take insulin every day. Even on fasting days insulin has several other jobs besides keeping one’s daily food based blood sugar within range. So on fasting days, I take 8 units of long lasting insulin, which is called a basal dose, to give my body the insulin it needs to do those other things.

    But then, I also take another 1.5 units of short acting insulin in the morning, again fasting or not. The reason for that small amount of insulin is to replace old insulin that my liver is actively clearing out. As I understand it, the liver significantly increases its removal of insulin from the blood starting a little before you awake up until about 3 or 4 hours later. Thus, if I did not take that small dose, my blood sugar would rise significantly even though I’m fasting. Maybe that is the difference between morning and evening insulin levels?

  17. I can also say that the timing of that early morning bolus shot of insulin is obviously based on my circadian rhythm. When I fly across time zones, my blood sugars take a definite hit, both higher and lower. You just never know.

  18. It makes evolutionary sense that ghrelin would be low in the morning and insulin response higher at night. (1) 10,000 ya humans still saw better during the day and so hunted then (as you described). (2) Low ghrelin means lower hunger in the morning, so less distraction to “get to work”. (3) Then you hunt a mammoth, which probably took a while, and (4) come evening, you’re feasting. Insulin is higher then so that we store that mammoth, rather than digest and burn it off. Then when some calamity comes along and wipes out our food, we have enough stored for the extra time and energy needed to migrate and survive, and be able to reproduce after that.

    This is a good example of how we can’t take 10.000 ya human dietary behavior, which evolved to maximize our chances at survival and reproduction, and apply it *directly* to *treating* hyperinsulinemia.

    Also, to the fat-shamers: If you’re smart enough to read and follow this blog, you’re smart enough to know that “low carb” isn’t a 100% cure-all. No one ever said it was. Pull your head out, open your eyes, and put your smarts into communicating productively about this.

  19. Dr. Fung,

    Thanks for another very interesting post. You’ve provided yet another piece of evidence that contradicts conventional wisdom. I don’t know how many times I’ve heard medical / dietary professionals state that it’s all about the calorie balance and has nothing to do with timing. 🙂

    If insulin levels are higher after an evening meal versus a morning one, does this mean that corresponding blood glucose levels must be lower x hours after eating in the evening versus the morning? If so, is it possible that this is simply the body’s way of keeping more glucose available in the blood for use throughout the day? After an evening meal, there is much less chance of the same amount of glucose being needed as sleep is not far off. In the evening is it simply more “suitable” to store than keep on tap?

    I was told many years ago by a wise engineering professor that to find the best way to do something, one should try first to find a biological analog. Either evolution or God in his infinite wisdom has already provided us with the most efficiently tuned and optimized mechanisms possible.


  20. Please block this Grashow “gentleman”. His attacks add no value. I feel sorry for such a sad and childish individual. His latest comment above is shameful.

  21. In the post linked above by the “gentlemen” he mentions starvation numerous times. Dr. Fung has never endorsed starvation. Fasting is NOT starvation. I wonder if he also trolls Dr. Goldhammer, Loren Lockman and other fasting proponents with such negativity.

  22. If anyone wants to know more about Mr.Charles Grashow………Please visit his twitter postings…..

  23. Interesting. When I was in my 20’s away from home I experienced real hunger. I would go for days with nothing to eat. Long story short when I returned home at 90lbs for the next several years I struggled to gain any weight. Doc said I had hypoglycemia. Me a 5’0 female age 21 I was eating 3000+ calories per day and not gaining. By age 30 I finally weight a healthy 115lbs. In My 30’s I went from the 115 to 138. Doc told me at age 21 If I kept eating sugar I would someday get diabetes too bad he is not around anymore.
    In my 40’s I went all the way to 180. I am now pre diabetes and after reading all your articles I will stop eating the breakfast I never wanted to start with. I gained 45lbs in one year at age 42 and I have been trying to understand why every since. I also starting eating breakfast after gaining all that weight at the advice of everyone else.
    So glad I found this blog.

  24. Fine tuning, fantastic! Our 2 meals a day will be breakfast and lunch in future, previously 11h00 and 18h30.

    We changed my husband’s diet after been admitted to hospital in Jan 2015 with heart failure. I attended the LCHF convention in Cape Town in Feb 2015 and immediately embarked on the LCHF Banting ketogenic style diet-no fruit, no grains, fasting. Of the 50kg he lost, the fluid from ascites was about 20kg. His ejection fraction was 26, now in January 2016 it is 54. His HbA1c was 5.9% this week, from a HbA1c of 9.1% in April 2015 on 60U of insulin and 1mg Novo-norm. After about 2 months on the diet he was off all diabetes medicine. By now the loose teeth he still has left after losing about all of them due to diabetes and diabetes treatment, grew fast as well as no more neuropathy!

    I have been following your advice and reading every bit from your pen and listening to all your videos. We only used the advice from you and the low-carb community, this was followed with loads of ridicule from doctors, e.g. “Dr Google is not always right”, and “the banting diet is going to make me rich”, these remarks from a cardiologist and internist.

    We had no other assistance from doctors or dieticians, therefore thank you once again for all the posts, blogs, videos, research references, etc.

  25. I have a question about blood sugar levels. I having been doing this WOE since Oct 2014. I lost 48 lbs. In April 2015 I fell off the wagon seeking my old sugary/wheaty comfort foods along with much alcohol, when my husband was diagnosed with a rare form of pancreatic cancer. By June he was given days to live. Well he is still around (thank God) and I have gotten my act back together and started focusing on me and getting well as of January 1, 2016. Since then I have been diagnosed with early stage kidney disease. In the past I was told I was prediabetic. I have been following Dr. Jason Fung’s blog and decided I needed to get my insulin resistance under control quickly. I have been using IF for about 6 days. Yesterday my fasting blood sugar was 3.7. In looking on the web that is apparently hypoglycemic? 2 hours after eating my blood sugar was 5.7mmol/L. I had eaten 8 net carbs and 30 grams of fat and 20 grams of protein. So my question is, What should blood sugar levels look like when a ketoer is fasting, upon rising or later in the day when intermittent fasting?

  26. Dr. Fung,

    Energy is not a thing, it is not stuff, it is not tangible, nor is it intangible. Energy itself is not ANYTHING. I cannot stress that point enough.

    Energy is a property, a concept ONLY. Energy is only a very abstract human mathematical construct, nothing more. It has no existence in reality. Assigning it existence in reality is overdoing it and totally wrong. Calories do NOT even exist. They have NO EXISTENCE in reality. Calories cannot be turned into matter, or human tissue of any sort. Fire is NOT energy. Fire is a cloud of hot particles HAVE energy. Huge difference. Nothing is “made of energy. ” Energy itself is NOT ANYTHING.

    Take care,

  27. More on Honey Razwell & nothingness…..about Nothingness……..

  28. Here’s something that I don’t see anyone else mentioning. It could be because it doesn’t affect anyone else. But it just might, so I want to share it.
    Some time ago I went from three to two meals per day. After a couple of years I went to one meal per day around 2 pm. I did this for just over six months. It took me that long to figure out that eating only in the afternoon made me gassy, i.e., I had more flatulence.
    So, I then went to an alternate-day plan with day 1 being breakfast only at 7:15 and day 2 being breakfast at 7:15 and lunch at 1:00 pm. The gas went away and this is how I eat currently (on most days).
    Here’s my interpretation. I measure my blood sugar (blood glucose) frequently and inject insulin. One of the great things about taking frequent blood sugar measurements is that I can get a very accurate understanding of my digestion from them.
    What I have found–and this is very common among diabetics, and, perhaps, most people–is that food eaten early in the day leaves the stomach rather quickly. Food eaten later in the day takes longer to leave the stomach. (More technically, gastroparesis tends to occur more later in the day.)
    Blood glucose rises after a meal, usually, only after the food (technically “chyme”) leaves the stomach, is broken down further, and begins to be absorbed through the small intestine into the bloodstream.
    Food eaten at breakfast is quickly absorbed into the bloodstream. Food eaten later in the day takes longer to be absorbed into the bloodstream.
    Now, when I was eating one large meal per day in the afternoon, all my food was sitting in my digestive tract a relatively long time. Maybe this caused the gas (perhaps through SIBO–small intestinal bacterial overgrowth–but that’s a whole ‘nother thing). When I eat in the pm only on alternate days and only after having eaten a breakfast earlier, I am eating fewer calories so there is less stuff sitting around to be fermented.

  29. Dear Dr. Fung!
    What about Warrior Diet by Ori Hofmekler?
    There is absolutely different approach In his intermittent fasting style book – ancient greek/roman warriors ate mostly at evening/night time, so u have to expand no eating period at day time lowering insulin and eat a lot at evening in 4 hour window when you’re less stressful and less cortisol!

    I am confused

  30. I’ve been fasting 16+ hours daily and eating moderate carbs for the last 2.5 years, lost 40kg and now normal BMI and waist:height ratio <0.5. After reading the research on individual blood glucose responses to foods depending on gut microbiota variations (Zeevi et al, Cell 2015; 163: 1079) I invested in a blood glucose meter. Although fasting BGs are good (around 4.2 mmol/l) I was shocked to find my post meal BG is higher than it should be with the peak delayed. After a pork and veg meal containing, carbwise, a half cup of cooked brown rice and chickpeas, taken with a glass of wine, and followed by around 3 tbsp stewed apple (ie with a little added sugar) with full fat greek yoghurt, my BG went up to 8.4 mmol/l at 2 hours after eating, and at 3 hours was 5.5. Next morning BG was 4.2 and remained low until lunch. After lunch BGs reach around 7 at 2 hours (lunch carbs typically include 1 slice of bread, 1 apple and 2 squares 70% chocolate, taken with plenty of healthy fats and protein). My question is: should I be worried about these 2 large glucose spikes a day or should I be cutting carbs further? Maybe especially in the evenings? If BG is low from 3 hours after dinner for at least 13 hours does that provide protection from the spikes???

  31. my english is bad I’m brazilian and I speak portuguese, please read all, it’s important

    man you are losing an important point as you are only thinking about weight loss and not about the big picture,

    we should eat 7:50pm and eat less, because is the time of the day our body wants the food, grehlin is high, so we can save resources… spending less on food… it’s like, obvious…

    I love your work, I read fasting 1 to 17 and gonna read today thru the end… but in this topic ypu are wrong, sorry… regards!!

  32. Kok-Hong Wong

    This research on time restricted eating by Salk Institute is interesting

    The paper…

    • I am looking forward to reading more about Time restricted feeding.
      From the short animal studies it seems with small eating windows the differences between low or high carbohydrate diets and animal or no animal diets fade. If an A TO Z study was done looking at feeding window then analysed we might know more about the relative effects of time restricted vs macro nutrients on health and longevity.

  33. Roger Bird

    No tigers were ever around around a herd of zebra sleeping away in the hot African sun, unless there are tigers in the Nairobi or some other African zoo.

    What a goose!!!

  34. This is really fascinating for me because I highly suspect I have Delayed Sleep Phase Disorder, a circadian rhythm disorder that puts my natural sleep schedule later than everyone else’s. So for me skipping breakfast means not eating my noon meal and having my first meal of the day between 4-6pm, and my last meal between 10-12pm. What you’re saying definitely still applies, eat the larger meal of the two as my first meal of the day instead of my second. But how would this fit with the advice to break a fast gently? I fast 16-17 hours per day between 11:30pm and 4:30pm the next day. I’m guessing that since it’s only a 17 hour fast the advice to break a fast gently isn’t as important as longer fasts. So it makes sense to me to at least make both meals relatively equal, if not making the first one slightly larger, so as to avoid a larger second meal. This was fascinating, thank you!

  35. Side note on the regional (Mediterranean & North America) comments:
    – Americans each much more in the day than most Europeans. And have much earlier dinners. In France, Spain, Italy and most of the Mediterranean, dinner is huge and late (8pm at the earliest).

  36. How are these times of higher insulin response and times of increased hunger affected by shifting amounts of daylight hours throughout the year? In our evolutionary past presumably circadian rhythms were attuned by African day/ night? Do we now adjust to local daylight or is 7.50 pm a fixed time regardless?

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