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