Energy Expenditure, Physical Activity, Body Weight and Body Composition

Abstract

It is difficult to keep up high-intensity training with a higher body weight, as described in the foregoing chapter. There is a complicated interaction between physical activity and body weight. Body movement requires energy as produced by muscles. Thus, there is an interaction between physical activity, body weight, body composition and energy expenditure. To move, one uses muscles and energy as stored in body fat. Excess weight in heavier subjects usually implicates excess body fat, limiting weight-bearing activities like running. In addition to body weight and body composition, physical activity is a function of predisposition and environment. There typically are those that are always on the move and those you cannot get on the move. The main part of variation in physical activity between individuals can be ascribed to predisposition. Physical activity affects body composition and to a lesser extent body weight. Additionally, the effect is age dependent. Children and young adults that become more physically active through exercise training show little or no weight change but do have changes in body composition. They get less fat and more muscular. The active elderly subject is not less fat and more muscular than a same aged more sedentary person. It seems difficult to overcome muscle loss with increasing age. However, a physically active lifestyle does improve muscle function and thus reduces fall-risk in elderly people. Overweight does not induce a proportional increase in activity induced energy expenditure and is associated with a reduction of body movement. Underweight is associated with a reduction of body movement through a loss of physical capacity. Chronic disease reduces physical capacity as well, possibly through a limited energy supply.