“Why diets don’t work: An internal “thermostat” may be the reason diets don’t work. A set of neurons in the brain stops mice from burning calories when they are not eating enough. This might prevent people from burning fat while on a diet (eLife, doi.org/b7gk).” (New Scientist, 2017, p.5).

This headline sounds great, but one must be careful when reading this. A human may be inclined to compensate by overeating after a period of under-eating (the concept most people consider a diet!). To state that if one does not eat they will not burn calories is somewhat misleading – one will still burn calories although at a much reduced rate.

Consider forced starvation (an extreme diet) which affects, for example, prisoners of war or victims of famine who may receive little or no calorie intake for days, weeks or months, they most definitely do lose weight.

If your not sure what Brown Adipose Tissue (BAT or Brown Fat) is, then read this article on Wikipedia which also describes White Adipose Tissue (WAT, commonly known as White Fat).

“Energy dissipation through interscapular brown adipose tissue (iBAT) thermogenesis is an important contributor to adaptive energy expenditure. However, it remains unresolved how acute and chronic changes in energy availability are detected by the brain to adjust iBAT activity and maintain energy homeostasis. Here, we provide evidence that AGRP inhibitory tone to iBAT represents an energy-sparing circuit that integrates environmental food cues and internal signals of energy availability. We establish a role for the nutrient-sensing mTORC1 signaling pathway within AGRP neurons in the detection of environmental food cues and internal signals of energy availability, and in the bi-directional control of iBAT thermogenesis during nutrient deficiency and excess. Collectively, our findings provide insights into how mTORC1 signaling within AGRP neurons surveys energy availability to engage iBAT thermogenesis, and identify AGRP neurons as a neuronal substrate for the coordination of energy intake and adaptive expenditure under varying physiological and environmental contexts.” (Burke et al., 2017).

References

New Scientist (2017) 60 Seconds: Why Diets Don’t Work. New Scientist. 27 May 2017.

Burke, L.K., Darwish, T., Cavanaugh, A.R., Virtue, S., ROth, E., Morro, J., Lui, S-M., Xia, J., Dalley, J.W., Burling, K., Chua, S., Vidal-Puig, T., Schwartz, G.J. & Blouet, C. (2017) mTORC1 in AGRP neurons integrates exteroceptive and interoceptive food-related cues in the modulation of adaptive energy expenditure in mice. https://elifesciences.org/articles/22848.