Part of the story of weight loss is understood in terms of metabolism. The food we eat is turned into energy to support our basal metabolism needs and also to support physical activity. If we eat more food than we need, the body stores the surplus as fat. Basal metabolic rates differ from person to person. Therefore, two people can eat the same amount of food over a lifetime, and one person is slender while the other is overweight.
Exercise builds lean muscle mass.
By developing the amount of lean muscle you have, you can actually burn more calories even while resting. In general men's basal metabolic rates are about 15 percent faster than women's. The more physically active you are, the more calories you burn. You must burn 3,500 calories to lose one pound. Just sitting around and watching TV burns between 1 and 2 calories a minute.