Many women exercise to reduce body fat. Shedding body fat can be more challenging for women compared to men, primarily because women need a certain amount of body fat for normal reproductive function. If females lose too much body fat, particularly if they’re exercising and restricting calories, levels of sex hormones like estrogen that affect fertility drop. This leads to menstrual cycle changes and changes in fertility or even a complete lack of menstruation. These changes sometimes happen to women athletes, especially runners, who train hard and get down to a very low body fat percentage. The drop in estrogen can lead to other problems such as loss of bone density and an increased risk for osteoporosis.
What Determines Body Fat Percentage Anyway?
Body fat percentage is simply the weight of the total fat you carry on your body divided by total body weight. If you weigh 120 pounds and have 30 pounds of body fat, your body fat percentage would be 30/120 or 25%. There are a number of ways to measure body fat percentage with varying degrees of accuracy including skin-fold calipers, with a bioelectric impedance scale, underwater weighing or with a DEXA scan. DEXA scan and underwater weighing are more accurate than skin-fold measurements and bioelectric impedance scales, but they’re also more expensive and time-consuming.
Women Need a Certain Minimal Amount of Fat for Health
The fat women need to maintain their menstrual cycles, fertility and a baseline level of health is called “essential fat.” The essential fat that women need is between 10% and 13%. When body fat drops below these levels, it can trigger health problems including loss of menstrual periods and fertility and lead to a decrease in bone density and an increased risk for osteoporosis and fractures. So, what’s a “healthy” body percentage for women? Based on the American Council on Exercise between 21% and 31% is considered healthy for women, but this doesn’t take into account age.
The council guidelines consider women in this age range who fall below 21% to be “underfat,” a term that means underweight from a fat standpoint. It’s still common for women athletes to be below 21% body fat, and most female fitness competitors have body fat percentages that are lower than this with no ill effects. On the other hand, when a woman’s body fat percentage falls below 13%, it can trigger physiological changes that lead to bone loss and menstrual cycle changes, especially if a female is restricting calories and spending a lot of energy working out, putting them into a catabolic state.
Ideal Body Fat Percentages Vary with Age
Although 21% to 31% body fat is considered a healthy body fat range for women, it doesn’t distinguish by age. Muscle mass declines with age and body fat increases, so there’s more leeway in what’s considered healthy. Women under the age of 30 would probably be considered most healthy with a body fat percentage in the low 20s, while women in their 40s and 50s would still be healthy if they were at the higher end of this range, in the mid-20s to low 30s. The average body fat for women as a general group is between 26% and 29%.
Body Fat Percentages in Female Athletes
Ever wonder what the average body fat percentages of female athletes are? Long-distance runners average around 17% body fat, swimmers around 18.5%, while volleyball and basketball players are in the 23% range. Female long-distance runners who compete at a national level average around 15% body fat. Tennis players? About 22%.
The Bottom Line?
There is an essential amount of body fat that women need to maintain health and fertility. Once you fall below 13%, most women will be at higher risk for health problems. Once your body fat rises above 31%, your risk for health problems of a different nature starts to rise – the risk for obesity-related problems like heart disease and type 2 diabetes. It’s not a good idea to focus on body fat but measure it periodically to make sure you’re in a healthy range.
ACE Fitness. “What are the guidelines for the percentage of body fat loss?”
Exercise Physiology: Energy, Nutrition and Human Performance. Fifth Edition. 2001.