Question: what percentage of body weight should be muscle mass?
Answer: According to Withings, normal ranges for muscle mass are: Ages 20-39: 75-89 percent for men, 63-75.5 percent for women. Ages 40-59: 73-86 percent for men, 62-73.5 percent for women. ages 60-79: 70-84 percent for men, 60-72.5 percent for women.