More evidence that weight control is determined by much more than ‘calories in/calories out’

There’s no shortage of awareness about the burgeoning rates of overweight and obesity afflicting Westernised countries. There are two principle theories about what causes obesity:

1.     It’s all about calories in/calories out

Proponents of this theory state that body weight is simply a function of the calories we put into our body (food and drink) and those that are burned during the processes of metabolism and activity. This theory is very much a conventional view, and has underpinned weight management advice for several decades.

2.     It’s more complicated than just calories

Some say that calories in and out does not adequately explain the burgeoning rates of obesity. The idea here is that there are hormonal (and perhaps other) factors that predispose towards deposition of fat in the fat cells that go way beyond the simple ‘calories in, calories out’ theory.

Just for the record, I’m a believer in the second theory. One reason for this is that science shows that taking a purely calorie-based approach to weight loss very rarely yields any significant success in the long term. And I’ve met hundreds of people who attest to this too. On the other hand, I’ve seen many, many individuals forget about calories, eat properly, and lose excess fat in a way that is sustainable in the long term.

The other thing is that there are some experiments that suggest that body weight is simply not all about calories in and out. For example, just over a year ago I wrote about a study in mice that found that mice eating when the would normally be asleep or inactive got fatter than mice eating at normal times. The surprise (for some) was that this greater weight could simply not be explained by the calorie principle.

Such a study is unlikely to be as relevant as a human study. However, in the absence of relevant research, there is no doubt that animal experiments of this nature ask serious questions about the validity of the calorie-principle, and strongly suggest other important factors affect body weight.

I was very interested to read another study published this week that is in a similar vein.

This study, again in mice, assessed the relationship between light exposure and body weight [1]. Mice were kept in one of three different lighting conditions:

1.     16 hours of light and 8 hours of dark per 24 hours (to simulate ‘normal’ light/dark phasing)

2.     24 hours of light

3.     16 hours of light, followed by 8 hours of ‘dim light’

This last condition is perhaps most interesting, as it sort of parallels the human condition where we can be exposed to light (street lights, domestic lighting, LED displays, etc.) when we are asleep (or should be asleep).

Food intake and activity was also assessed in all the mice. The results showed that, over time, mice kept in conditions 2 and 3 got significantly fatter than those in conditions one. In other words, exposing mice to light at times when it would normally be dark led to weight gain.

Well, perhaps the explanation is that these mice ate more and exercised less. Actually, the results did not support this idea. So, again, we have evidence that something other than ‘calories in and calories out’ has influenced the weight of these mice.

One other factor that was different was the timing of eating. Relatively speaking, mice exposed to dim light ate proportionally more during the light phase of their day than mice living under ‘normal’ conditions (condition 1). Mice are nocturnal animals, and generally do their eating at night. In short, therefore, there was an association between eating at a time when eating is not usual and enhanced weight gain. This result is consistent with the results of the study linked to above.

In an effort to probe further the relationship between the lighting conditions, eating pattern and weight, the researchers restricted the food supply to when the mice would normally eat (night-time). When they did this, mice did not get significantly fatter.

In summary, therefore, exposing mice to light at night caused them to eat more at an abnormal time (during the day), and this appeared to cause weight gain in a way that was not explained by caloric balance.

Now, if we were to apply the same concept to humans, we might be open to the principle that ‘unnatural’ light exposure could lead to eating at abnormal times which could lead to enhanced risk of obesity. In the case of humans, we might want to avoid over-eating in the evening.

I generally counsel against big meals in the evening. A couple of strategies tend to work well here, without the need for constraint:

1.     Eat breakfast (preferably a protein rich one)

2.     Have a snack of something satisfying (such as some nuts) in the late afternoon or early evening


1. Fonken LK, et al. Light at night increases body mass by shifting the time of food intake. Proceedings of the National Academy of Sciences. 11 October 2010 [epub before print publication]

14 Responses to More evidence that weight control is determined by much more than ‘calories in/calories out’

  1. Hans Keer 13 October 2010 at 9:07 pm #

    In this case I would disagree with you. A better strategy would be:

    1 Abstain from breakfast (intermittent fasting)
    2 Don’t eat the nuts, this are omega 6 bombs, rather have some meat or fish as a snack.

  2. ben 13 October 2010 at 9:13 pm #

    Protein breakfast and a snack dinner, but what about lunch?

    Also, with the time change, it gets dark after 5pm, would this be time after which any eating should be avoided?

    Not that calories may matter, but it seems like a very low calorie diet!

  3. Robert 14 October 2010 at 5:31 am #

    I’m definitely a proponent of the calories in, calories out theory. The ONLY time I have ever been able to lose weight is by creating a caloric deficit, either through diet or diet and increased activity. The type of food eaten seems to be irrelevant. Its about the calories. At least, for me it is.

  4. Reijo Laatikainen 14 October 2010 at 8:06 am #

    Very interesting post. Your conclusion on the effect of evening eating on weight management gets support from from epidemiological studies done among shift workers. Midnight shift workers do not follow natural dietary and sleep rhythm, their meal pattern is shifted towards evening and night. Indeed, shift work is linked to metabolic syndrome and obesity (for example, see )

  5. simona 14 October 2010 at 2:50 pm #

    I think Dr. Briffa is suggesting strategies that reduce your appetite in the evening to avoid overeating at night. He didn’t mean to say eat only protein for breakfast and only a snack in the evening. The snack would be the fourth meal for those who go a long time between lunch and dinner and end up eating a lot at dinner time.

    Hans Keer
    2. (re omega 6 ‘bombs’) I thought so too but it’s not that simple. It depends how fresh the nuts are, what type of nuts, how many, how much omega 6 one is eating during the day, how much omega 3, omega 3/6 index in tissues, and I’m sure other things too, it’s not just avoid nuts all together. Plus not all LA is converted to AA.

  6. Nigeepoo 14 October 2010 at 7:43 pm #

    The energy balance equation doesn’t work if some of the terms are left out. Exercise activity (TEA) is only one term determining energy out. There’s also BMR/RMR, TEF & SPA/NEAT. Any of these could have changed in the test subjects when their Circadian rhythm was disturbed.

    Although I am in the “calories do count” camp, counting calories is often futile if the wrong diet is eaten, as hunger for food often overpowers logic (unless you have strong willpower).

  7. luis martinez (61,mexico) 15 October 2010 at 12:49 am #

    What is working well for me,after 5 months of succssefull weight loss and energy gain,plus improve sleep quality is; Breakfast=3 eggs (2 whites),plus dried meat shredded or bacon in lard or butter (ghee) mix with coconut oil 50/50,probiotics plus fibe,Lunch=beef stew,Dinner=Salad green with butter,plus ofal or fish (alternated)with coffee or relaxing tea with whey protein powder.I’ve even had to cutt 1/4 of my thyrioid med.(hipoth’sm. Please forgive my english.

  8. jane 15 October 2010 at 1:35 pm #

    …so would sleeping in an eye mask result in weight loss?

  9. John Shead 16 October 2010 at 11:22 am #

    I have recently purchased your book ‘Waist Disposal’ and have started following the excellent advice in it and have already (after only 2 weeks) started loosing weight (hopefully fat) and if this continues at the same rate (2 lbs per week) I shall be very happy. Following your advice which makes perfect sense to me since you explain the scientific principles behind what you suggest, I find that I no longer snack on all the wrong things between meals and, no longer, find that I feel hungry at times. Thank you for such excellent advice.

  10. Mat 17 October 2010 at 8:58 pm #

    @ Robert who is a proponent of the ‘Calories in, calories out’ theory.

    Please could you provide evidence of how this will work in the long term after your body has reset its basal metabolic rate to account for the calorie deficit.

    A vast proportion of people who are advocates of the ‘calories in, calories out’ theory seem to think that the laws of thermodynamics apply – They then totally mis-quote both the first and second laws as a massive and erroneous statement of ‘Energy in = energy out’.

    Granted, initially in a calorie-restricted diet, you will lose weight but this will slow down and stop when the body adjusts its calorific needs and then the only way to lose weight is to lower your calorific intake – rinse and repeat…

    All of this is working against your body! what is needed is to provide the body with an opportunity to lose weight. Adipose tissue is made up of triglyceride (three fatty acids bound with a molecule of glycerol) and the primary way that triglycerides are produced is by eating processed carbohydrates. Diet is, or should be about ‘unstoring’ adipose tissue and to do this, one would need to encourage the body to use triglycerides as an energy source. The best way to do this is to eat mainly proteins and fats (non-processed).

    If you are interested in reading about / studying the effects of calorie-restricted diets; search the internet for ‘The Minnesota Starvation Experiment’ – The results are quite eye-opening.

  11. Robert 25 October 2010 at 2:12 am #


    There is mild calorie restriction then there is calorie restriction as practiced by following a CRON diet. Evidence? I use the Okinawans traditional diet as a prime example of mild calorie restriction and their health and longevity record speaks for itself! I agree with you about long-term excessive calorie restriction. The idea that calories aren’t important leads people to the false impression that they can eat as much as they want.

  12. David 27 October 2010 at 6:16 pm #

    I bought John’s book in May and have lost a lot of weight by ‘inceasing’ my calorific intake.

  13. Robert 2 November 2010 at 1:06 am #


    My mind isn’t closed to the concept and your suggestion of looking into ‘The Minnesota Starvation Experiment’ has peaked my interest.

  14. Rosie 22 January 2011 at 4:12 pm #

    It might help to look at things another way – eating “properly” affects the brain and appetite differently than eating junk. The addictive effects of some parts of modern diets are a real issue, as anyone who has eaten a whole packet of MSG or yeast extract containing biscuits when they planned to stop at a small handful will tell you. Ditto for me for chocolate anything (except 70%+ dark chocolate, strangely).

    So eating a traditional (pre-industrial or ‘Mediterranean’ if not paleo) diet is probably more likely to work anyway because it reduces appetite and cravings, probably reducing calorie intake as a side effect. It may lift mood and reduce sluggishness, making exercise easier also. My experience is getting started is the hard part and then the ball starts to roll by itself.

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