Too much eating while stressed leads to faster weight gain

Weight is often presented as a simple math: eat excessively a certain number of calories and you will gain a corresponding amount of body fat; under-eating a number of calories, you will lose a corresponding amount of body fat.

It's a neat idea on paper – but in the real world, biology is rarely so neat.

The types of calories you consume can affect how much fat you will gain or lose. So can the time of day when you eat them. And according to Australian scientists, your stress level could also have a powerful effect.

A team at Sydney's Garvan Institute of Medical Research found that mice fed a high-calorie diet gained more weight when stressed than when their lives were easy to live with.

"While it's bad to eat junk food, eating high calorie and stressful foods is a double whammy that promotes obesity," said Professor Herbert Herzog, laboratory manager. eating disorders in Garvan.

"This study indicates that we need to be much more aware of what we eat when we are stressed, to avoid faster development of obesity,"

Their study is published in the journal Cell metabolism.

The researchers noted that when they were stressed, most people eat more than they would – and that, whether they eat too much or not enough, people stressed are more likely to consume "very appetizing foods".

It's basically the code for junk food – those high in calories, fat and sugar and low in nutrients. (Nobody has ever taken a bucket of comforting salad after a breakup or a hard week at work.)

The Garvin team sought to determine the mechanisms behind this behavior by feeding mice with normal, high-fat foods that were normal and stressed. (If you are curious about how to stress a mouse: in this study, they were placed briefly in cages filled with one centimeter of cold water.)

The stress-related weight gain has finally been linked to a brain molecule called neuropeptide Y, or NPY, that mice and humans produce in response to stress. According to the article, NPY "exerts a powerful orexigenic effect" – or, translated into English, stimulates appetite.

The researchers confirmed the link between stress, obesity and NPY by stopping the production of the molecule in the amygdala – the region of the brain that processes the emotions – thereby reducing the weight gain of the mouse.

"Without NPY, weight gain in a high-fat diet with stress was identical to weight gain in a stress-free environment," said lead author of the study, Dr. Kenny Chi Kin Ip, in a statement.

Ip and his team found that when they were both stressed and fed with high fat diets, the mice had levels of insulin – the essential hormone this tells the cells to absorb excess sugar from the blood and sends the brain the signal to stop eating.

These supercharged levels caused the insensitive desensitization of nerve cells from the amygdala, which eventually stopped detecting it completely. This then stimulated the production of NPY by the nerve cells, which caused even more food consumption and slowed the metabolism of the mouse.

"Our results revealed a vicious cycle: high chronic insulin levels, stress-related, and a high-calorie diet favoring more and more food," Herzog said.

When most people think insulin they think Diabetesbut the hormone goes well beyond this condition. Herzog said he was "surprised" by the magnitude of the role played by the insulin imbalance in this study, an effect that he and his team hope to explore further in their future research.

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