Attività
Physical Activity, Obesity and Health
Epidemiology of obesity: occurrence, causes and consequences
Thorkild I.A. Sørensen,
Professor of Clinical Epidemiology, Director of the Institute of Preventive Medicine, University Hospital, Copenhagen, Denmark
The ongoing global epidemic of obesity is assumed to be due to the prevailing obesogenic environment promoting physical inactivity and overeating. However, the development of the epidemic shows heterogeneity in time and place that cannot be explained by corresponding differences in the obesogenic environment in the usual sense. In addition to the well established genetic susceptibility, there is evidence suggesting that there may be a lasting susceptibility that is induced by some environmental influences acting very early in life. If true, this gives promises of a feasible prevention in a narrow time window.
The role of physical inactivity in development of obesity is complex, and difficult to investigate properly because of the confounding by the dampening effects of obesity itself on physical activity. On the other hand, physical inactivity undoubtedly plays a major role for development of the obesity complications such as insulin resistance, impaired glucose tolerance and diabetes mellitus type 2. The long-term role of physical activity is, however, difficult to separate from the effects of weight changes, which by them selves influence physical activity.
The well-known relation between obesity and risk of morbidity and mortality may need to be qualified. Thus, most if not all health damaging effects of obesity seem to be a consequence of abdominal obesity, whereas the remainder of the body fat stores, especially in the gluteo-femoral region, in fact may have beneficial health effects.
Weight loss produces immediate improvements in risk indicators, but the long-term effects in the general population is more doubtful. Weight loss is associated with increased mortality, usually ascribed to confounding by underlying diseases or health damaging behaviour, but even intentional weight loss in healthy overweight subjects, induced by dieting, may have health damaging effects showing up in excess mortality. Combining the weight loss program with physical activity may reduce the long-term health risk of weight loss.
