So the more muscle you have the higher your metabolic rate the less muscle you have the lower your metabolic rate and fewer calories you burn. This explains why it is crucial to protect your metabolic rate and not have muscle loss. Loss of muscle also leads to loss of tone underneath the skin leaving you soft and unshapely with no form or contour. If you lose weight too rapidly your skin wont have time to adjust either. Also muscle is what gives you strength and loss of it means a weak body.