We carry two kinds of fat in our bodies. “Essential fat” is stored in small amounts in bone marrow, organs, the central nervous system and muscles, and is needed for the normal, healthy functioning of all these body systems. “Storage fat” is stocked for energy. For men, essential body fat makes up about three percent of total body weight. For women, the percentage is higher – about 12 percent – because it includes amounts in the breasts, pelvis, hips and thighs believed necessary for normal female reproductive function.
For a woman of 25, a healthy amount of body fat ranges from 16.5 to 24.6 percent; less than 14 percent is considered a health risk. The amount of body fat considered healthy can increase with age, to 19.8 to 30.4 percent for women between 40 and 59 and to 23.2 to 31.3 percent for those 60 and older. The healthy ranges in men are from 10.5 to 21.3 percent for those age 20 to 39, from 17.4 to 24.6 percent for those between age 40 and 59, and 19.7 to 25.2 percent for those 60 and older.
We now believe that the minimum body fat percentage for women should range between 13 and 17 percent, although there’s no hard and fast rule on what is too low for an individual. One sign that your body fat is too low is disturbance of regular menstruation. If your periods stop, nature is telling you that you don’t have enough body fat to nurture a fetus should you become pregnant. Please don’t think of this as a convenient method of birth control – it isn’t. You need normal hormonal function for more than just menstruation and fertility. For example, bone health in women depends on adequate circulating levels of estrogen.
Regardless of age, the average healthy adult body fat range is 15 to 20 percent for men and 20 to 25 percent for women. Women with more than 32 percent body fat and men with more than 25 percent body fat are considered to be at increased risk for some diseases.
Be aware that when body fat percentage gets too low, exercise performance actually declines, and you can be at risk of nutrient deficiencies, fractures, illness, less tolerance for cold, as well as loss of reproductive function. As long as you continue to menstruate and have enough energy, your body fat percentage probably is OK. If not, you should try to gain a few pounds.
Andrew Weil, M.D.
Melanie Schorr et al, “Sex Differences in Body Composition and Association With Cardiometabolic Risk,” Biology of Sex Differences, June 27, 2018, DOI: 10.1186/s13293-018-0189-3