The Challenge: People gain weight for different reasons as they age. Chief among them is a decline in physical activity. When you move less, a greater number of calories get stored in the body as fat, instead of getting converted into energy to fuel activity. What’s more, we naturally lose muscle mass as we age — upwards of 3-5% after age 30 if you’re inactive — which, in turn, leads to a slower metabolism.
The Solution: Strength training can help put the brakes on the loss of muscle mass, as well as build new muscle. Since muscle cells are far more metabolically active than fat cells, they burn more calories. As you increase your muscle mass, you also boost your metabolism.
Be sure to warm up before training, and start slow to build strength without injuring yourself. Begin with two sessions a week of 10 reps of 8–10 different exercises for the upper and lower body and the core. Utilize your own body weight for things like pushups and pullups and 5- to 10-pound dumbbells for other exercises. You should feel like you can’t do more than an extra rep or two at the end of each exercise — if you can, it’s time to increase the weight.
Source: My Fitness Pal