Why Do We Gain Weight as We Age?
As we age, a decrease in our physical abilities leads to a decrease in our metabolic rate (amount of energy used in a given period), which in turn contributes to weight gain. The physiological changes that accompany increasing age affect the body's composition and cardiopulmonary (heart and lung) function, thus reducing our ability to work and exercise and lose weight. Genetics, muscle mass, gender, calorie consumption versus expenditure, and lifestyle are all factors in weight gain.
Changes Occurring with Age
Behaviors such as frequent dieting have been shown to affect the resting metabolic rate and your weight. Individuals who diet frequently have a significant decline in their basal metabolic rate. This decline is prolonged and sustained for several months and cannot be attributed to that expected from a loss in muscle mass or fat free mass. Periods of extreme starvation can produce as much as a 45% decline of the metabolic system. Studies have shown that calorie restriction in short-lived animal species not only causes a decrease in the basal metabolic rate but also an increase in lifespan. Studies are now underway to evaluate calorie restriction in humans and its effect on longevity.
Physical activity refers to body movements that result in the production of energy. The type, frequency, and duration of activity, as well as rate of progress, should be considered when choosing an exercise program. Physical activity has been shown to decrease the occurrence of some chronic diseases. There is a large body of evidence that the risk of death from disease is decreased in individuals who are physically active. The strongest evidence of this has been shown for coronary artery disease. There is moderate evidence that physical activity decreases the risk of hypertension, obesity, colon cancer, noninsulin-dependent diabetes, and osteoporosis. Physically active individuals have been shown to perform daily activities with less effort.
Unfortunately, there is not an age-related decline in appetite. Most individuals consume calories in excess of requirements, resulting in weight gain over the years. To prevent this age-related gain in weight, considerable motivation is required. One has to avoid the imbalance between calorie consumption and expenditure and consider the effects of aging while maintaining a healthy lifestyle.
William E. Roundtree, MD