Abstract

It is without question that the prevalence of overweight and obesity has seen unprecedented increases over the last several decades. One of the largest contributors to body weight change is an imbalance in the energy consumed and energy expended, wherein weight gain results from a positive energy balance and weight loss is induced by a negative energy balance. The components of energy balance include energy intake, energy expenditure, and energy storage. Traditional representations of energy balance assume static models wherein energy intake minus energy expenditure equals energy storage and thus body weight. Contrary to this model, energy balance is hugely dynamic and far more complex. Each component interacts with each other and is differentially regulated by multiple metabolic, physiological, and behavioural systems. Both dietary and exercise interventions have been shown to affect energy balance and thus body weight; however, biochemical and physiological compensatory responses to each may attenuate weight loss or make it difficult to achieve weight maintenance—further work is needed to delineate these mechanisms and generalize to populations with varied demographic characteristics. With the advance of technology in the last few decades, several innovative methodological opportunities have emerged that can provide a more comprehensive understanding of energy balance, body weight and composition, and the impact of lifestyle interventions.