Could eating late in the day promote weight gain in a way that has nothing to do with calories?

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A mere 10 days ago one of my posts highlighted a study which had, apparently, found that a low carb diet was found to induce increased amounts of atherosclerosis (a key underlying process in the development of cardiovascular conditions such as heart attacks and strokes) in mice. I was sceptical of this study, partly on account of the fact that mice are not men (or women), and using them as a model for human disease is not always advised. There is also the matter of the huge volume of research which attests to the fact that low-carb diets have a range of favourable effects in humans, including weight loss and several markers of disease including blood fat, blood sugar and insulin levels.

However, I do not dismiss animal studies out-of-hand. I will and do refer to them sometimes when they genuinely appear to enhance our understanding of the relationship between, say, nutrition and health. For example, in my very last post I referred to a rat study which showed that artificial sweeteners appear to have the capacity to induce (not protect against) weight gain, compared to sugar.

And it’s another animal study that I want to talk about today. It concerns the feeding of nocturnal mice in two distinct ways [1]. Some mice were fed unlimited amounts of food (a high-fat diet) during the night (the normal eating time for these mice). Other mice were fed during the day (when they would normally be asleep). Food intakes and activity levels were measured over a period of 6 weeks. These were found not to differ significantly between the two groups.

With these facts as they are, one might expect the weight status of the two groups of mice to be the same. After all, calories in and out of these mice appeared to be pretty much the same. However, the results appear to defy the calorie principle, in that the mice eating during the night were found to have increased their weight by 20 per cent. The other group (eating at a time when they should, by rights, have been asleep) had, however, amassed an additional 48 per cent of their original weight.

This study suggests that there is something about the timing of eating that may influence whether it is metabolised or ends up being stored (as fat or something else) in the body. It also does cast some doubt on the ‘wisdom’ that weight status is all about the ‘calorie in and calories out’. Interestingly, there is some evidence that night-eating (consuming proportionately more of the diet during the evening and night) is associated with increased body weight [2].

Those keen to moderate how much they eat during the evening and night may be interested in research which shows that packing in food intake earlier in the day seems to put a natural brake on eating later on. In one study, the diet diaries of almost 800 men and women were examined [3].

Their food and calorific intake was assessed for each of five, four-hour periods stretching from 6 am to 2 am the following day. The results of this study showed that those who had consumed the bulk of their food near the end of the day ate, on average, significantly more calories than individuals who ate more substantial amounts of food early on. In addition to assessing food intake over the course of each day, the researchers also calculated how effective each meal was at sating the appetite. The so-called ‘satiety index’ of each meal was calculated by dividing the number of calories it contained into the time that elapsed before another meal or snack was eaten. Interestingly, food eaten later in the day was found to satisfy less, calorie for calorie, than food eaten earlier in the day.

One other thing that can really help to stave off unnecessary eating in the evening, in my experience, is to make sure hunger has not run out of control by this time. For most people, all this takes is to have a snack in the late afternoon, preferably of something that has true appetite-sating ability. A handful or two of nuts will normally do it.


1. Arble DM, et al. Circadian Timing of Food Intake Contributes to Weight Gain 3rd September 2009 [epub ahead of print]

2. Colles SL, et al. Night eating syndrome and nocturnal snacking: association with obesity, binge eating and psychological distress. Int J Obes (Lond). 2007;31(11):1722-30

3. de Castro JM. The time of day of food intake influences overall intake in humans. Journal of Nutrition 2004 134:104-111

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