ABSTRACT
Overweight and obesity are associated with an increased incidence of and mortality from a wide range of chronic illnesses. However, as yet the relative contribution to these problems of inadequate physical inactivity and an excessive intake of food remains unclear. Moreover, there is a possibility of reverse causality, with disease conditions reducing habitual physical activity and thus causing obesity. Nevertheless, obesity apparently has a substantial impact upon prognosis in a number of chronic diseases. The largest effect is seen in type 2 diabetes mellitus, where gross obesity increases mortality 6.3-fold in men, and 3.5-fold in women. Longitudinal studies further suggest that the risk is increased if a person gains weight, and is decreased if body mass is reduced. The overall effect associated with obesity is a 70 to 80 per cent increase in premature mortality, and this provides a strong argument both for maintaining an acceptable body mass and for correcting any excessive accumulation of body fat through tactics that should include both an increase of physical activity and a restriction of food intake.
