An adiposity force induces obesity in humans independently of a normal energy balance system-a thought experiment

Obesity in humans represents a cumulative retention of a tiny fraction of total energy intake as fat, which is accompanied by growth of the metabolically active, energy-demanding, lean body mass. Since the energy balance regulation operates irrespective of the excess fat storage, availability of the required energy supplies is a permissive condition for obesity development. It occurs predominantly among people genetically predisposed and/or living with social or mental challenges. I propose a theory in which the body responds to social disruptions as threats of a future lack of food by an adiposity force building a reserve of energy independent of the regulation of the energy balance. It is based on the assumption that our evolutionary development required collaboration in gathering and sharing of food, combined with precautionary measures against anticipated failing food supplies. Social challenges are perceived as such threats, which activate the adiposity force through the brain to instigate the growth of fat and lean mass by neuro-hormonal signalling. If both perceived social threats and food abundance continue, the adiposity force pushes the fat accretion process to continue without inhibition by feedback signals from the fat mass, eventually leading to more obesity, and more so among the genetically predisposed.This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

Automated summary

Human obesity is caused by the accumulation of a small portion of energy intake as fat, accompanied by growth of lean body mass. The energy balance regulation is not related to excess fat storage, but rather to the availability of energy supplies. Obesity predominantly occurs among individuals genetically predisposed and/or facing social or mental challenges. The proposed theory suggests that social disruptions are perceived as threats of future food shortages, leading the body to build up energy reserves through fat accumulation independent of the energy balance regulation.