Define Physical activity as a factor for obesity?

Sedentary life style with lack of an exercise schedule tends to make one obese. As we approach middle age, our physical activity generally decreases without a corresponding decrease in food consumption leading to obesity. Activity may be decreased because of a debilitating illness like arthritis or cardiac disease. A change of occupation or simply because of the fact that period of quiet, rest and relaxation have increased, may lead to decreased activity. In addition, when we are more active, the body prefers to metabolize fat as an energy source leading to a decrease in the adipose tissue.