Understanding the development of obesity

Abstract:

Obesity, defined as excessive accumulation of body fat, is usually considered a result of positive energy balance. This refers to the 1st thermodynamic law specifying that the energy content in a closed physical system is the cumulative difference between input and output of energy. For obesity, this implies the energy stored as fat in the body is a passive result of an energy intake that has exceeded the body's energy requirements to maintain basal metabolism and physical activity. While the 1st thermodynamic law is valid as a quantitative description of the relations among energy intake, expenditure and storage, it is not really helpful in understanding the development of obesity. This straightforward application of the energy balance concept implicitly involves an assumption that storage of fat in the adipose tissue is a passive process. There is growing evidence that this is not the case. I discuss a theory based on accumulation of adipose tissue based on active regulation of fat storage through integrated higher brain functions responding to psychosocial stimuli. Consideration of this theory may allow more comprehensive synthesis of the existing evidence, and suggest future research and novel opportunities for prevention and treatments.