Food tricks the body: how fats disrupt biological rhythms

Researchers from the University of California, San Francisco (UCSF) came to this conclusion after studying how saturated and unsaturated fats interact with the body's circadian rhythms. The results are published in the journal Science.

The scientists found that the type of fat consumed - especially saturated fats, such as hydrogenated oils in snack foods - directly affects the functioning of a protein called PER2, which regulates metabolism and the biological clock. This protein "decides" whether the body needs to store or burn fat, centred not only on the length of daylight hours, but also on the composition of food.

How the body "feels" the change of seasons

In nature, many mammals, such as bears, increase their food intake in summer and lose their appetite in winter. Until recently, day length was thought to be the main cue. But a new study in mice has shown that saturated fat in food can "trick" the body into thinking it is summer and activate energy storage - even if it is deep autumn.

According to Professor of Neuroscience Louis Ptacek, co-author of the study, "if there is still plenty of food around in autumn, the body receives mixed signals: on the one hand, the days are getting shorter, on the other hand, saturated fats tell the body to keep eating."

Plants do produce more saturated fats in the summer, and animals eating them get the signal: "the season of plenty continues". As winter approaches, the composition of fats changes - plants produce more unsaturated fats, which better helps them tolerate the cold. This shift in diet is an additional "switch" that helps the body go into "lean mode."

An experiment with mice and fatty foods

In the experiment, mice were placed in conditions that mimicked the changing seasons: first equal day and night (12 hours each), then "summer" with 20 hours of light and "winter" with 20 hours of darkness. Some groups were fed a moderate diet, while others were fed a high-fat diet.

It turned out that the mice on the high-fat diet adapted poorly to winter conditions: they emerged from hibernation later and showed disrupted activity rhythms. This was particularly evident when consuming hydrogenated fats found in processed foods.

What this means for humans

Although the study was conducted on mice, scientists believe that similar processes can occur in humans. With modern lifestyles - with constant artificial light and year-round access to high-calorie foods - our internal 'seasonal' clocks are disrupted. This can be one of the causes of sleep disorders, obesity, diabetes and other chronic diseases.

"Even one festive cupcake in winter can trick your body into thinking it's summer - and you'll reach for a second one tomorrow," warns one of the paper's authors, postdoc Dan Levine.

The study emphasises the importance of not only calories, but also the composition of fats in the diet. Regular consumption of saturated fats can interfere with the body's natural rhythms and prevent it from adapting to the changing seasons.