1. The more muscle you have, the higher your base metabolism will be and the more calories you will burn even at rest.
2. Second reason is more important. Whenever you lose weight, you will lose some muscle along with the fat. If you don't exercise and do some strength training, up to 30% of the weight you lose can come from muscle loss, that isn't likely to be healthy over the long haul.
Good strength and muscle tone are essential for functional living and health. You can hold your muscle loss down to 3-5% total weightloss with moderate strength training.
Strength training helps to preserve bone density, balance, and many other important things.
Strength train each muscle group at least twice a week--this really only takes about 30-45 minutes per workout. Better yet, try circuit training, where you lift weights without resting between sets. This method meets both cardio and strength requirements because you keep your heart rate elevated throughout your workout, increasing the amount of calories you burn per workout.
Lifting Heavy is the Key to Weight Loss. We know that losing fat involves increasing your metabolism. What you may not know is that muscle plays a huge role in raising metabolism. A pound of muscle burns about 10-20 calories a day while a pound of fat burns 5 calories. That means any growth in your muscle tissue is going to help you burn more calories all day long. In fact, strength training has all kinds of great effects on your body like: