
Most adults lose about ½ pound of muscle each year after the age of 20. Muscle mass is associated with metabolism. Muscle burns calories at a higher rate than fat, so the more muscle you have, the more efficient you are (and the more you need to eat). Resistance training builds muscle to prevent or reduce muscle loss and help improve metabolism – a key to maintaining your weight.
Benefits of Resistance Training
In addition to the physical appearance benefits, here are some of the other benefits shown in the literature:
Improved blood pressure
Increased bone density
Improved metabolic function
Improved balance and shock absorbency
Improved body composition
Increased strength of muscles and connective tissue which decreases the risk of injury.
http://www.nwhealth.edu/healthyU/getMoving/resistance.html