I'd go so far as to say that it doesn't matter how thin you are. If you don't have muscle fitness, you're not in shape. Aerobics may burn calories and improve cardiovascular stamina, but weight training provides multiple benefits. Weight training also builds greater support for one's spine, which can straighten posture and ease chronic back pain. In addition, greater strength builds greater confidence, said DiBrezzo.
Women tend to feel empowered and more self-reliant when they know their muscles are in shape.