Physical activity is highly important to human beings because it has many benefits that result in improvements in health. Physical activity is required for the maintenance of a functioning physiology and mental health is increasingly being linked to physical activity. However, the ability of exercise to cause weight loss in the obese is controversial, and has not been conclusively proven. Many studies conflate exercise and dietary variables and lack suitable controls, and therefore the conclusions that can be drawn from such studies are clouded by confounding variables and uncertainty. It is assumed that physical activity causes weight loss because it is assumed that excess energy intake is the cause of weight gain. However, high energy foods are often low quality foods, and low quality nutrition that contains refined starches and modified fats can drive insulin resistance and cause weight gain. The addition of exercise to a poor quality diet may yield comparatively poor results compared to dietary changes alone.
Many studies have compared diet with exercise, and also with diet plus exercise. The results of such studies often show that adding exercise to dietary changes yields no better results in terms of weight loss when compared to dietary changes alone. For example in a meta analysis of such studies1, authors compared the weight and fat loss effects of diet group (energy restriction), with exercise only groups, with exercise plus diet groups. The results of the analysis showed that weight loss and fat loss was not significantly different in groups who undertook just dietary changes compared to dietary changes plus exercise (weight loss was 11 kg in both groups and fat loss was 8 and 9 kg in the diet and diet plus exercise groups, respectively). The fat loss and weight loss in the exercise only group was significantly less than the diet and the diet plus exercise groups. Exercise therefore has no additional fat or weight loss effects when added to dietary changes alone, and yields comparatively poor results in isolation.
While the diet group in this study was defined as those who had undertaken energy restriction, such studies often also add changes to normal food intake, emphasising healthier foods, which confounds the results somewhat. Data from studies showing weight loss with just improvements in diet and no energy restriction suggest that it is these changes that drive weight loss, not the energy restriction. Energy restriction diets by definition restrict sugar and modified fats, and these changes may in turn cause improvements in insulin sensitivity and this may lead to weight loss. However, while exercise for weight loss is not proven, exercise does provide other less controversial and more fully understood benefits. Exercise is vital to the health, but the idea that exercise involves joining a gym and spending hours running on a treadmill like a hamster is founded on no real scientific basis. If exercise is seen as a health benefit rather than a weight loss tool, then it allows other more successful avenues for weight loss to be explored.
RdB
