Stating the obvious, we typically eat different foods at different times of day. But why should that be so? While much of this variation is likely down to cultural factors, the dietitians also have plenty to say on the matter of what we should be eating when, in order, for instance, to lose weight. There is undoubtedly much cultural variation in the kinds of foods that different people like to eat at different times of day, as anyone who has stumbled across the sticky, slimy fermented soy bean dish known as natto at the breakfast buffet in Japan will know only too well. How could anyone contemplate eating that first thing in the morning?

Breakfast is often described as the most important meal of the day. It provides sustenance and energy (i.e. calories) for the day ahead, or as nutritionist Adelle Davis famously put it back in the 1960s: “Eat breakfast like a king, lunch like a prince and dinner like a pauper.”1 Supporting this suggestion, a 2013 study documented a 27% increase in coronary heart disease amongst those North American men who regularly failed to eat breakfast, and a 55% higher incidence amongst those men who ate after going to bed compared to those who did not.2 The general advice, then, is to eat a substantial well-balanced breakfast. There are, however, those who have other ideas: One Japanese researcher, for instance, recently reported that eating ice-cream when you wake-up helps make you smarter (at least temporarily – it increases Alpha brain wave activity in the brain, apparently). However, although this story was widely covered in the global press, it is hard to find a peer-reviewed academic research study to back this particular claim up. Perhaps this is because Prof. Kago only compared brain activity in those who ate ice-cream with those who ate nothing. Hence, it is impossible to say for sure whether it was eating ice-cream, or just eating ‘anything’ at all, that led to effects he reported.3

Meanwhile, back in 2012, Israeli researchers garnered almost as much media attention with their suggestion that complementing one’s regular breakfast with a slice of chocolate cake could help reduce sweet pangs later in the day.4 The suggestion was that a slice of cake (or rather, a high carbohydrate and protein breakfast) might even help you to lose some weight. This one sounds just too good to be true as well, doesn’t it? However, beyond the cultural factors and the latest dieting trends being peddled by the health consultants, one can ask whether there are any more fundamental factors at work, governing what we eat when, during the day. There are certainly a number of important diurnal variations (circadian rhythms)5 that may underpin, at least in part, our food behaviours/ preferences.
The most important of these may well be the diurnal changes in our ability to detect sweetness. Research shows that we are most sensitive to sweetness in the morning, while finding it significantly harder to detect this taste in food and drink at the end of the day. Interestingly, however, there is no such variation for the other basic tastes (salt, sour, bitter, or umami). It turns out that our recognition threshold for detecting sweetness is tied to circulating plasma levels of the hormone leptin; the suggestion being that the change in sweetness perception may help regulate food intake.6 Our mood also shows some degree of variation over the course of the day, and this might exert some influence over the food choices we make too. And finally, it wouldn’t surprise me to find that the diurnal variation in the pattern of ambient sensory stimulation might also play some small role in biasing our food behaviours.7

So, in conclusion, there are undoubtedly some profound cultural differences in the kinds of foods that people want, or think it appropriate, to eat at different times of day. However, beyond these cultural factors, and the latest recommendations from the dietitian’s, there are also more fundamental psycho-physiological reasons as to why consumers may be drawn to different foods at different times of day.8 Rest assured that many of the major food companies out there selling breakfast cereals are eagerly trying to figure out how to make their products more appealing for consumers at other times in the day (e.g. for lunch and dinner). Meanwhile, there are also many other food companies who would dearly love to break into the breakfast market and so increase their sales. While achieving this goal is none too easy, paying attention to the fundamental psycho-physiological changes taking place in all consumers over the course of the day provides a start. It is an interesting question for bakery professionals to consider how they too can also achieve this cross-over in sales, by changing the way in which the products are marketed so that the consumers may be tempted to eat them throughout the day, rather than just for breakfast, say.

References below


Sifferlin, A. (2013). When to eat breakfast, lunch and dinner. Time, July 23rd. http://time.com/4408772/besttimesbreakfastlunchdinner/.


Cahill, L. E., Chiuve, S. E., Mekary, R. A., Jensen, M. K., Flint, A. J., Hu, F. B., & Rimm, E. B. (2013). A prospective study of breakfast eating and incident coronary heart disease in a cohort of male U.S. health professionals. Circulation, 128, 337-343.


For critical coverage of the reporting of this industry-funded ‘study’, see Letzter, R. (2016). A viral story that claimed eating ice cream for breakfast will make you smarter points to a bigger problem in health journalism. Business Insider, November 30th. http://www.businessinsider.com/donteaticecreambreakfast201611.


Jakubowicz, D., Froy, O., Wainstein, J., & Boaz, M. (2012). Meal timing and composition influence ghrelin levels, appetite scores and weight loss maintenance in overweight and obese adults. Steroids, 77(4), 323-331; Pettit, H. (2016). Eating ice cream for breakfast could make you SMARTER. Daily Mail Online, November 23rd. http://www.dailymail.co.uk/sciencetech/article3964054/SobrainfreezeEatingicecreambreakfastmakeSMARTER.html. See also http://www.telegraph.co.uk/news/health/news/9069276/Chocolate-cake-breakfast-could-help-you-lose-weight.html.


Aschoff, J. (1965). Circadian rhythms in man. Science, 148, 1427-1432. Intriguingly, the rate at which we spontaneously salivate also shows significant diurnal variation; We essentially stop salivating while we sleep. See Spence, C. (2011). Mouth-watering: The influence of environmental and cognitive factors on salivation and gustatory/flavour perception. Journal of Texture Studies, 42, 157-171, for a review.


Nakamura, Y., Sanematsu, K., Ohta, R., Shirosaki, S., Koyano, K., Nonaka, K., Shigemura, N., & Ninomiya, Y. (2008). Diurnal variation of human sweet taste recognition thresholds is correlated with plasma leptin levels. Diabetes, 57, 2661-2665.


E.g., natural daylight has a warmer hue at the end of the day than at the beginning, as any photographer knows only too well (see Collins, J. F. (1965). The colour temperature of daylight. British Journal of Applied Psychology, 16, 527-532). My suspicion is that the level of ambient olfactory and auditory stimulation also varies in predictable ways over the course of the day, and that this may be internalized as a slight change in the pattern of sensory dominance across the course of the day.


E.g., see Baertlein, L. (2015). Breakfastarians are feeding US restaurant growth. Money, August 4th. http://time.com/money/3984124/breakfast-restaurant-meals-mcdonalds-dennys-sonic/.

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