The Average Lean Body Mass

The human body is made up of many different materials including fat and lean tissue. Total body mass consists of body fat and lean body mass. Lean body mass includes more than two-thirds water, according to Medline Plus, and the remainder other lean tissues such as muscle, organs and bone. Body composition tests estimate body fat percentage. The average American’s body fat percent is higher than what is recommended.

Average Body Composition

The Average American’s body composition is different for men and women. This is because women naturally hold more body fat and men tend to have a larger amount of lean muscle mass. According to Medline Plus, the average woman in America holds about 22 to 25 percent body fat and the average American man holds approximately 17 to 19 percent body fat.

Body Composition Recommendations

People are considered obese if their body fat exceeds 30 percent for women and is 25 percent or higher for men. Medline Plus recommendations for body fat are 20 to 21 percent for women and 13 to 17 percent for men. In her book, "Sports Nutrition," Christine Rosenbloom states that body fat levels of approximately 10 to 22 percent in men and 20 to 32 percent in women are generally considered acceptable; she also states that in general, body fat percentages lower than 5 percent in men and 12 percent in women are not recommended.

Athletes

Many athletes have a higher percentage of lean body mass compared to sedentary individuals due to having more muscle and less body fat. Lean body mass in athletes varies depending on the sport they participate in. Athletes with some of the highest lean body mass and lowest body fat include runners and body builders. Rosenbloom states that male distance runners have body fat percentages of approximately 4.7 percent and female distance runners approximately 14.3 percent.

Older Adults

As the human body ages, body composition typically changes, as well. Older adults usually see an increase in body fat and a decrease in lean body mass, especially muscle tissue and bone density. Ways to help reduce changes in body composition related to aging include engaging in regular exercise, consuming adequate calcium and following a healthy, well-balanced diet, according to Medline Plus.

Body Composition Tests

Body composition tests can help to estimate an individual’s body fat percentage vs. lean body mass. Rosenbloom states that most body composition tests typically have an error of 3 percent to 4 percent, at best.

BMI, or body mass index, is usually a good estimate of body fat with the exception of extremely muscular individuals and older adults. The American Dietetic Association’s website provides an adult BMI calculator. Skin fold measurements are commonly used to help estimate body composition due to their low cost and ease of use. Underwater weighing, bioelectrical impedance, DEXA scanning, waist circumference and waist-to-hip ratios are other body composition tests available.