Over the years, someone who gains 30 pounds of body weight may have really lost 15 pounds of muscle and gained 45 pounds of fat. Weight training rebuilds this loss of muscle caused by years of inactivity. Weight training preserves muscle mass.
Posture improves and the body firms up.
The body uses oxygen better and the muscles and bones are stronger. Muscle strength is built by overloading the muscle. This means lifting more weight than one usually lifts. The body responds to this challenge by becoming stronger. One method of weight training rotates the areas of the body.