The increasing worldwide prevalence of obesity suggests that there is a chr
onic positive energy balance. This situation implies poor coupling between
energy intake and energy expenditure, but the contribution of each of these
factors remains unclear. Epidemiological data suggests that physical activ
ity has a role in the prevention of weight gain, although there is little e
vidence that it has a beneficial role in weight loss. High-fat diets have a
lso been implicated, evidence from a variety of sources suggests that diets
high in fat undermine appetite regulatory mechanisms. There has been much
research to investigate the coupling between energy expenditure and energy
intake in the short term in an attempt to elucidate some of the mechanisms
involved. However, mechanisms regulating appetite are very complex, and it
is currently unclear at which points physical activity and diet may have an
influence.