1. It boosts your metabolism.
A pound of muscle burns about six calories a day, while a pound of fat burns just two. So the more muscle you have, the faster you metabolize energy—around the clock.
2. It'll keep you young.
Starting around age 40, we lose about a half pound of muscle mass every year, and unfortunately, we tend to replace it with fat. Resistance training can counteract age-related muscle loss, keeping your weight down and making you feel (and look) years younger.
3. It's an excellent way to burn fat.
A recent study conducted at the University of New South Wales found that high-intensity intermittent exercise (like strength training) may be better for reducing both belly and under-the-skin fat than steady-state exercise (like jogging). This might be because beta oxidation—the process that breaks down fatty acids—increases during the recovery periods between activity.
4. It reduces arthritis pain.
This is true especially for your knees and back, in part because strong muscles help support and protect your joints and because building muscle promotes weight loss, which reduces pressure on your joints.
5. It keeps your mind sharp.
In 2010 researchers from the University of British Columbia reported that women between 65 and 75 who did resistance training once a week for a year improved their cognitive abilities by 12.6 percent. (The control group regressed slightly.) Lead study author Teresa Liu-Ambrose, PhD, has speculated that this may be because resistance training (like all exercise) improves blood flow to the brain, and also requires the brain to build new circuitry as you master new moves.
6. It strengthens your bones.
Researchers think weight-bearing exercise may induce biochemical changes that improve the body's ability to form bone tissue. A study of more than 61,000 postmenopausal women found that this kind of activity can slash a person's risk of hip fracture by 41 percent.
7. It helps control blood sugar.
In patients at high risk for diabetes, resistance training can decrease blood sugar levels by about 15 points—an enormous improvement. During exercise, the body metabolizes excess glucose for fuel.
Dr. Oz on Building Muscle: