Why the caveman in all of us makes yo-yo diets fail

IT’S the time of year when many of us overindulge, only to try to shed the weight in the new year.

But yo-yo dieting can make us fatter because of the caveman in us, scientists say.

Changes in consumption tell our hunter-gatherer brains that food supplies are unreliable and so they prepare for famine by telling our bodies to store extra fat, much like birds fattening up before winter.

The result is a spiral of dieting and weight gain, researchers from Bristol and Exeter universities say.

And those who yo-yo diet tend to gain more weight overall than those who never diet at all, they found.

Dr Andrew Higginson, senior lecturer in psychology at Exeter, said: “This happens because non-dieters learn the food supply is reliable so there is less need for the insurance of fat stores.”

The findings came from a mathematical model of animal responses to food supply.

The study suggests we use energy now in a similar way to hunter-gatherer humans, who lived more than 12 000 years ago and needed to build up fat supplies to avoid starving in winter.

The researchers modelled how our brains respond to a “good world”, where food is rarely scarce, and a “bad world”, where the supply is unreliable.

Yo-yo dieting, the model predicts, convinces us we are in a bad world, as our ancestors were. The brain then sends messages to the body to build up fat, so that, even if they lose weight on a diet, yo-yo slimmers often gain more overall, the study, published in the journal Evolution, Medicine and Public Health, found.

Professor John McNamara, a mathematician at Bristol University, said: “Our model shows weight gain does not mean people’s physiology is malfunctioning or that they are being overwhelmed by unnaturally sweet tastes, but uncertainty about the food supply triggers the evolved response to gain weight.”

The odds are against slimmers, the team said, because those who were overweight beforehand received brain signals of a “glut” of food, causing it to overcompensate further when a diet suggests food is in short supply.

And the hunter-gatherer response to the “famine’ of a diet can cause binge-eating afterwards, as it drives us to eat high-calorie food. – Daily Mail