Why do many diets fail? A team of scientists from the University of Cambridge publishes a study that reveals how our own brain activates its defense mechanisms in the face of lack of food and literally boycotts the diet plan.
” Weight loss strategies can be inefficient because the body works like a thermostat and associates the amount of calories we burn with the amount we have eaten,” explains Clémence Blouet, one of the authors of the work. “When we eat less, our body compensates for it and burns fewer calories , making weight loss difficult. We knew that the body is capable of regulating this caloric thermostat, but how it achieves it was a mystery.”
The researchers focused on a structure located in the hypothalamus that helps regulate the amount of food eaten. It is a group of neurons called AGRP (for its acronym in English: agouti-related neuropeptide neurons ) that when activated cause an increase in appetite, and when inhibited they decrease it.
Using a genetic trick to ‘turn off’ or ‘turn on’ these neurons , the authors of the work studied the behavior of mice located in special chambers in which energy expenditure could be measured in terms of temperature, and where the amount was varied. of food available.
The results revealed that AGRP neurons not only regulate appetite, but are also capable of influencing energy expenditure based on the amount of food available. When activated, the mice ate more, but when no food was available, the consequence was a decrease in energy expenditure, limiting the number of calories burned and therefore weight loss. As soon as food was available again, this effect was interrupted and energy expenditure returned to normal values.
It is therefore a mechanism that has lasted throughout evolution to defend ourselves in times of famine, but which today is a nuisance for people who want to lose weight. In them, the diet is not very effective, as the body compensates for the reduction in calories.
Then what do we do? “This study could help in the design of new therapies to combat obesity but, at least for those people who only need moderate weight loss, combining diet with increased physical exercise could be the solution”, concludes Luke Burke , another of the authors.
So, you know: the next time your diet fails, you can blame it on your neurons .
Reference:
Burke, LK et al. 2017 mTORC1 in AGRP neurons integrates exteroceptive and interoceptive food-related cues in the modulation of adaptive energy expenditure in mice. eLife, DOI: 10.7554 / eLife.22848
