Energy expenditure and obesity

Understanding energy and macronutrient metabolism is critical to the understanding of obesity, especially etiology, relationship between genetic and environmental influences, and approaches to prevention and treatment. The importance of fat balance to obesity is emphasized, and this is first established by an analysis of energy and macronutrient balance based on known human physiology and then backed up by clinical studies. The known metabolic risk factors for body weight gain are briefly summarized, and the emerging pattern of their relationships with weight gain is described. The metabolic responses to weight loss are also examined, along with the question of possible metabolic adaptation to a hypocaloric diet. Since the fat balance concept has major implications for the prevention and treatment of obesity, some overall directions for these areas are presented.