Metabolism is the process your body uses to burn calories for energy. Because metabolism naturally slows with age, you may need fewer daily calories as you get older. But your metabolism doesn't dictate your weight. To lose excess weight, include physical activity in your daily routine. The calories you'll burn will help promote weight loss. Second, start a strength training program. Muscle tissue burns more calories than fat tissue does, even when you're at rest. Whether you use hand-held weights, resistance tubing or another type of resistance, you'll reduce your body fat, increase your lean muscle mass and burn calories more efficiently.