We Have Subconscious Urges to Over-Eat During the Winter

By Sondra Forsyth

If you find that you are tempted to eat more than usual when the temperatures drop, you’re not alone. A study done at the University of Exeter in the UK found that people have evolved to have subconscious urges to over-eat, and limited ability to avoid becoming obese –and that this propensity is more prevalent during the winter.

A release from the university notes that there is not yet an evolutionary mechanism to help us overcome the lure of sweet, fatty and unhealthy food. and avoid becoming overweight for understandable and sensible reasons, according to researchers. This is because in the past, being overweight posed less of a threat to survival than being underweight. The urge to maintain body fat is even stronger in winter when food in the natural world is scarce in many parts of the world.

The researchers used computer modeling to predict how much fat animals should store by assuming that natural selection gives animals, including humans, a perfect strategy to maintain the healthiest weight. Their model predicts how the amount of fat an animal stores should respond to food availability and the risk of being killed by a predator when foraging.

The model shows that the animal should have a target body weight above which it loses weight and below which it tries to gain weight. Simulations showed that there is usually only a small negative effect of energy stores exceeding the optimal level, so subconscious controls against becoming overweight would be weak and therefore easily overcome by the immediate rewards of tasty food.

The release quotes lead author Dr Andrew Higginson, from the College of Life and Environmental Sciences at the University of Exeter, as saying, “You would expect evolution to have given us the ability to realize when we have eaten enough, but instead we show little control when faced with artificial food. Because modern food today has so much sugar and flavor the urge humans have to eat it is greater than any weak evolutionary mechanism which would tell us not to.

“The model also predicts animals should gain weight when food is harder to find. All animals, including humans, should show seasonal effects on the urge to gain weight. Storing fat is an insurance against the risk of failing to find food, which for pre-industrial humans was most likely in winter. This suggests that New Year’s Day is the worst possible time to start a new diet.”

The evolutionary model also shows that there is no evidence to support the “drifty gene” hypothesis, which some researchers have previously suggested would explain why some people become overweight and others do not.

The paper was published in January 2016 in Proceedings of the Royal Society B. It was written with John McNamara from the School of Mathematics at the University of Bristol, and Alasdair Houston from the School of Biological Sciences at the University of Bristol.