Chronic positive mass balance is the actual etiology of obesity: A living review

The fundamental cause of obesity is widely assumed to be an energy imbalance between calories consumed and calories expended (i.e., the energy balance theory). However, this century-old obesity paradigm is fallacious. According to known laws of physics, the actual etiology of obesity is chronic positive mass balance, not positive energy balance. Furthermore, the relevant physical law in body mass regulation is the Law of Conservation of Mass, not the Law of Conservation of Energy. It is important to understand that energy balance and mass balance are separate balances in the human body. Since calories simply represent the heat released on food oxidation, they have no impact on body mass. Body mass can only change as a result of net mass flow; thus, the only food property that can augment body mass is its nutrient mass, not its energy content. The recently proposed mass balance model describes the temporal evolution of body weight and body composition under a wide variety of feeding experiments, and it seems to provide a highly accurate description of the very best experimental human feeding data. By shifting to a mass balance paradigm of obesity, a deeper understanding of this condition may follow in the near future. The purpose of this living review is to present the core issues of the upcoming paradigm shift and some practical applications related to the subject.