How often should we eat?

There has been some recent interest, even in the mainstream media, in the practice of ‘intermittent fasting’. Essentially, this means going for extended periods of time without food. It comes in many different guises. Skipping of significantly delaying breakfast is one approach. Contracting the ‘window’ available for eating each day to, say, 6 or 8 hours is another approach. Still another is to alternate days of no food or very limited intake with days during which eating is unrestricted.

One of the theories about why intermittent fasting might have benefits concerns the hormone insulin. When we eat, insulin is generally secreted. This hormone helps sweep nutrients such as glucose (sugar) out of the bloodstream and into the body’s cells where it can be ‘burned’ for energy. Fat, in this scenario, is believed to less likely to be metabolised for energy. In the ‘fasted’ state, though, insulin levels are relatively low, and this might help fat-burning, as least in part because when insulin levels are low fat is more likely to be released from fat cells and be available for metabolism.

Theory dictates, therefore, that very regular eating might keep insulin levels chronically (persistently) elevated and increase our risk of running into weight issues. On the other hands, less frequent eating may count in our favour.

All the theory in the world does not really matter in the end, though, because if we want to be sure that reduced meal frequency is beneficial somehow it needs testing. Earlier this year Dutch scientists undertook an interesting study in which the effects of different meal frequencies were tested on a group of 12 healthy men [1].

On one occasion, the men were fed a diet (15 per cent protein, 30 per cent fat, 55 per cent carbohydrate) for 36 hours, with the food split into three meals a day. On another occasion the same food was eaten, but this time it was split into 14 portions each day. This second approach is certainly extreme and does not generally reflect what frequent eaters do in practice. However, sometimes in experiments it can make sense to use very different approaches (in this case 14 ‘meals’ versus 3) to maximise the chances of detecting some difference.

One of the things that the researchers measured was the ‘oxidation’ (metabolism) of fat and carbohydrate. They hypothesised that eating 3 meals a day might shift metabolism from sugar towards fat for the reasons discussed above. In this study, though, they did not see such a shift.

However, other differences were seen between the diets. Notably, the amount of sugar that appeared in the bloodstream was lower when the individuals were eating the 3-meal-a-day regime. This suggests that the lower meal frequency enjoyed better blood sugar control overall (a good thing), and something that the authors suggest may contribute to improved weight control over time.

But there’s more: the reduced eating frequency was also found to lead to improvements in the resting metabolic rate compared to the more frequent eating. This, in theory, may also assist weight control efforts in the longer term.

The other notable difference was that when eating 3 times a day (compared to eating 14 times a day), individuals were less hungry and felt more sated. The authors comment that:

The [different] responses between smaller and larger eating occasions may simply be due to the inability of the body to detect the size of a smaller eating occasion as an adequate physiological load, reducing or eliminating the eating related responses typically observed when larger eating occasions occur.

Or to put it another way, the small ‘meals’ were not big enough to properly satisfy the appetite.

Though interesting, this study has some limitations. It studied a relatively small group made up of healthy men. A larger group might have yielded more significant results. However, we may have got different results in women or individuals who are overweight/obese and more likely to be ‘metabolically deranged’ and therefore different that the individuals studied here. Nevertheless, the study is useful in that it provides at least some evidence which supports the idea that lower meal frequency may have benefits for individuals.

This study was not a test of intermittent fasting, but provides some evidence that challenges that are sometimes made that ‘little and often’ is the best way to eat. My experience is that those needing to eat this way are often foods that simply don’t sustain them very well perhaps because of their relatively low-protein, low-fat, and blood sugar disruptive nature. Examples include breakfast cereal, cereal bars, ‘healthy’ meal replacement bars and sandwiches.

What is the ideal frequency to eat? I think it depends on the individual and perhaps that individual’s circumstances. In general, though, I’d follow these two basic guidelines:

  1. don’t eat if you’re not hungry
  2. don’t allow yourself to get too hungry before you eat

The thinking behind point 2 is that if people get very hungry, they find it harder to eat healthily.

When I started experimenting with intermittent fasting a year or so ago, it occurred to me that my previous beliefs about our ‘need’ to eat three times a day were just wide of the mark for me and, as it turns out, a lot of other people now. I now encourage a much more fluid approach based on the two guidelines above. One thing it’s done for me and others is to liberate us from the supposed need to eat by the clock. The benefits can be huge. In general, taking a more fluid approach seems to lead to people eating less, having more time, and being less preoccupied with food. These are usually big pluses for people.


1: Munsters MJ, at al. Effects of meal frequency on metabolic profiles and substrate partitioning in lean healthy males. PLoS One. 2012;7(6):e38632. Epub 2012 Jun 13

24 Responses to How often should we eat?

  1. Stephanie 31 August 2012 at 1:45 pm #

    Hi Dr Briffa
    What about the regular (healthy) meals, 5 times a day, increase the metabolism, whereas semi-fasting slows down your body’s metabolic rate?
    Are there big advantage to increased metabolism? does it mean the body will burn more food and result in weight-loss?

  2. Maud 31 August 2012 at 1:49 pm #

    Dr Briffa,
    I think the 3-meals a day is deeply rooted in the culture and it’s liberating if this can change, making people listen to the signals/messages from their bodies. I’m curious on your view of intermittent fasting while adding fat (butter & coconut oil) especially for women and the effect on ketosis (and fat burning).

  3. Reijo Laatikainen 31 August 2012 at 2:15 pm #

    Another piece of evidence that supports 3 times a day scheme. A Harvard cohort:

  4. Ted Hutchinson 31 August 2012 at 2:47 pm #

    Maybe the reason larger meals provide more satiation is explained by this paper which shows that only when fat is detected SIMULTANEOUSLY at duodenal jejunal, ileal sites was secretion of Satiety parameters (hunger and fullness) cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), peptide YY (PYY) maximally activated.
    Length and site of the small intestine exposed to fat influences hunger and food intake.
    A larger meal would better enable all sections of the digestive tract to activate secretion of satiety hormones simultaneously and fully activate the ileal brake on consumption.
    Ensuring fat content is in each course, starter, main and dessert and possibly also with coffee/cheese may be the ideal for prolonged suppression of hunger.

  5. Craig 31 August 2012 at 3:04 pm #

    I would agree. There are days when I eat my last meal at 8pm and then I’m not hungry again until 6/7pm the next day. There are days when I eat my last meal at 8pm, and I’ll be hungry by 1pm the next day, or even upon waking. I don’t deny myself food as a matter of course – If I’m hungry, I’ll eat – but I do try to keep the fasting window open and eat less regular meals.

    My dad tells me skipping breakfast will cause diabetes. I tell him that I find that hard to believe; but I wouldn’t find it hard to believe that skipping meals is *associated* with diabetes, as such eating patterns (while fasting isn’t that mainstream) might imply an otherwise unhealthy lifestyle which might increase the incidence of diabetes.

    Cause and effect I guess. Bottom line for me: Eat when you’re hungry, and stick to what your body wants. Stick to high protein and fat, but if your body wants a few carbs stick to vegetables, and maybe some fruit. I also like the odd bit of brown soda bread.

  6. Ems 31 August 2012 at 3:20 pm #

    I have followed the intermittent fasting stories with interest, although as an ’amateur’ follower of your interesting blogs I apologise if this seems an obvious observation. Would it be the case that the body produces an insulin rush at the start of what it thinks is going to be a decent-sized meal and so causes the bloodstream to be overloaded with far more insulin than may be required, meaning that the total amount of insulin produced in 24 hours is far greater with 14 ’instigations’ than three. Apologies if I’m stating the obvious.

  7. tess 31 August 2012 at 3:40 pm #

    Stephanie, unless those five meals were mostly fat, you’ll have five insulin-spikes a day, during which you won’t be able to burn fat at all. you have to truly fast for three days before your metabolism slows — a few hours won’t do it. of course if you’re on a “starvation diet” of 1200 calories a day or less, your metabolism will slow down anyway. the situation is a lot more complicated than popular media would have us believe….

  8. Bev C 31 August 2012 at 4:42 pm #

    Before I retired I used to meet with the public on a one-to-one basis and frequently the conversation veered towards food. Of those who ‘never ate between meals’, ALL of them were of normal weight. I tend to be a nosher and am constantly struggling despite a healthy low-carb lifestyle. So this makes sense.

  9. Paleofast 31 August 2012 at 5:13 pm #

    I note that the test subjects were fed what I would call a high carb diet at 55%. Pity really that no such studies are ever carried out when subjects are fed a evolutionarily resonant diet such a paleo/lchf. I have reason to believe tehr esults would be rather different. Our ancestors were very unlikely to eat three meals a day…mostly because they needed msot of the day to provision/find food. We were lucky to eat once in 24 hours. I have recently been experimenting on msyself with this. I do a 20 hour fast starting at 22:00 the night before and going withour eating until 17;00 the following day every day for the last week or so. It has becom easier and easier and I feel great during the fast. The empty stomach sensation which before used to panic me and make reach for a snackl falls in teh background and I find I function really well.
    Something to ponder about

  10. Mrs P 31 August 2012 at 7:59 pm #

    I recently reached my goal weight and am maintaining. I found that in order to lose weight steadily I had to “keep the metabolism fire burning”. There are two ways to keep a fire burning. You either throw a big log on and hope it has staying power or you keep feeding it small logs. I prefer the small logs (requires portion control) because they are easier to digest and offer more variety. I eat about 5 times per day but I find if I am hungry and don’t eat my body starts to conserve energy and fat (low energy and weight plateaus). I wake up hungry which tells me that 8 hours of fasting seems to be enough for me. I also try to include a 2-3 ounce portion of protein and 1 tsp healthy fat (olive or coconut) at 3 of the meals, the other 2 are usually fruit or veggies. I don’t eat sugar, wheat or dairy (for the past 5 years) which I found keeps my liver clean therefore needing less fasting/detox. I feel great and take no meds, never get sick, etc.

  11. MikeS 31 August 2012 at 8:53 pm #

    I recently came across a BBC Two series, called “Eat, Fast and Live Longer,” that treats this subject. It’s a six part series that began in August. It focuses on the longevity effects of fasting, although the speculation here is relevant the apparent overall benefits of fasting. Here’s a link describing Part two of a six-part, six-hour series.
    Very interesting stuff. I’ve watched some of it on YouTube

  12. Siobhan 31 August 2012 at 9:49 pm #

    Thank you very much for this post. I’ve just completed my third week of Intermittent Fasting (IF) and have found it really interesting. Have already lost loads of weight and going to the gym 4 times a week I have been a bit stuck. Recently I changed my gym work outs to have more resistance based (weights) work and this, along with the IF have kick started things again. I am doing a 2/5 fast, so basically I fast by severely restricting calories, on Tuesdays and Thursdays and eat a sensible, low carb way of eating on the other 5 days. What I have found really interesting on the 2 IF days is that it really makes me question whether I am actually hungry, or just think I am. A cup of green tea later and the conclusion is always, no, I wasn’t hungry, it’s just habit. I’m not going to lie and say the two days are a breeze, but I do find myself curiously looking forward to the IF days and yes, it really has made a difference & I intend to carry on with it.

  13. Susan Wallace 1 September 2012 at 12:10 am #

    Thanks Mike S! I’ve just watched an hour of “Eat, Fast and Live Longer” and found it very interesting and mostly convincing but I’m concerned about the idea postulated in the programme that eating a lot of protein is bad news for the body. It would be interesting to know if you have any views on that Dr Briffa….? Meanwhile, a huge thank you for sharing so much of your research on this blog.

  14. Craig 1 September 2012 at 1:57 am #

    I recently finished reading Gary Taubes “Good Calories, Bad Calories”. He’s a science writer who, I believe, advocates very similar things to Dr. Briffa (I hope I’m not wrong saying that?)

    I can’t remember the exact page – but I remember reading something about the purported effects of a high protein diet on the kidneys and feeling satisfied that it was, in fact, a myth.

  15. Liz 1 September 2012 at 7:01 pm #

    I also watched the Horizon programme and was inspired to try intermittent fasting. My weight loss low carb diet began on 11 June. I was 74.5 kg and 164 cms. By 17 August I had lost 5.7 kg but had reached a plateau and had been the same weight for 3 weeks. So I tried intermittent fasting from 17 Aug, just Mon, Wed and Friday. Eating my normal low carb diet during Tues, Thurs and the weekend. I fast for about 24 hours. No breakfast or lunch but plenty of green tea and water then a meal of no more than 20 g carbs in the evening. Oh, and I have been drinking 250 mls of wine 2 or 3 times a week. Since starting intermittent fasting I have lost 3 kg so my total weight loss is 8.7 kgs. I am delighted. The fasting is easy as I have a busy job so I don’t notice not having lunch – quite hungry by supper time but not ravenous or sick with hunger. This is much easier than I thought and the results speak for themselves. Also it allows me to be more relaxed about my diet during my “feeding” days. I am going to stick to this pattern for the rest of my life as it may also have other health benefits on my risk of developing neurodegenerative diseases and heart disease. It all makes sense to me as our hunter gatherer ancestors would not have plentiful food all the time so the body is designed to be able to withstand periods of fasting and glut. The problem is that in out modern lives we are in the glut times all the time.

  16. Richard David Feinman 2 September 2012 at 12:35 am #

    Good post. I agree that intermittent fasting and especially not eating breakfast are worth trying. I was not so impressed with the study you cite and would tend to go with the studies on intermittent fasting as well as the extensive anecdotal evidence as in the comments. I think that one theoretical way to understand the problem is to appreciate the importance of kinetics (that is, timing) and the limitations of traditional, that is equilibrium thermodynamics (energy). The idea is that metabolism runs on rates and cycles, so if you allow fat to form and add then food before the fat cycles back to a starting point, the fat will accumulate, even if there is seeming energy balance — that is the consequence of living systems being far from equilibrium. We tried to bring this out in a theoretical paper available at After page 3, the writing is technical (and possibly pretentious) but the intro explains the problem and I think Figure 1 tells the story.
    The other reason for thinking that skipping or delaying breakfast is a good idea is that almost all dietitians advice against it.

  17. Lynn 2 September 2012 at 11:58 pm #

    Thank you for a simple understandable post.:)

  18. William L. Wilson, M.D. 3 September 2012 at 12:09 am #

    Hey John–I just returned from the Ancestral Health Conference at Harvard and there was a great deal of discussion about intermittent fasting. The general consensus was that the benefits of fasting are much greater on a high fat diet than on a high carbohydrate diet. By training your body to use ketones for energy, when you don’t eat you tend to burn fat rather than break down muscle to make glucose, the typical case when you are eating a high carbohydrate diet. Jimmy Moore is big on this type of diet and he seems to be experiencing a lot of personal success by following it. Of course we need more research before recommending this to our patients.

  19. Lorraine 3 September 2012 at 4:47 pm #

    Thank you for the article. I have been following a Paleo Diet for over 5 years and a strong believer of the benefits of intermittent fasting. I just wanted to add that shift workers might want to be careful of IF as it can cause extra stress on the body and, cause the opposite effect intended. I find IF works best on a day off, your not under too much stress and when you have had plenty of rest/sleep.

  20. Dave P 4 September 2012 at 8:38 pm #

    Dr Briffa since 2007 i have followed a lo carb diet, and it has been pretty much all positive. One of the strange things i experienced quite early on was an aparent lack of hunger. Initially it worried me some as i thought something must be wrong. But some 6 years down the line it is normal. I eat until i get a definite full feeling ( In terms of volume i actually eat a lot less per meal than previously) I have a reasonably active working life but can often go all day without anything more substantial than maybe a handful of nuts.
    Whilst i dont actually fast per se i do have long periods where i dont feel the need to eat.

  21. Adam 14 September 2012 at 1:55 pm #

    Before going on a real food diet, I had to eat 6 times a day, at least. The hunger was incessant and extremely demanding. Then I started a paleo diet, and I found myself only able to eat 3 meals a day because I simply wasn’t that hungry so often.

    Then I played around with my macros and am now eating a diet of mostly fat, some protein and very little carbohydrate. Since I tried this combo, I only have appetite for 1 single meal a day. There is simply no room for any more.

    A typical meal would be 1/2 block (250g block) of butter, a salmon fillet and a bunch of leafy/cruciferous veggies.

    I have lost 100 pounds and have melt the weight off for 3 years. I may be in my late 40s, but I have, for the first time in my life, visible abs. I went from size 40 pants to size 30.

    Eating at low frequencies, in my case once a day, definitely works for me when I watch my food quality.

  22. Tracey G 16 September 2012 at 10:12 pm #

    Having been a “breakfast” (as in eating within an hour of waking for the day) hater since I was a child – preferring to go until AT LEAST lunchtime (often much later) before eating – yet always being TOLD “breakfast” is the most important meal of the day, this article and its comments are very interesting! Would it be possible for you to post an article with your thoughts about ‘skipping’ breakfast and the effects it has on your metabolism, weight, health, hunger, etc?


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