Definition of Lean Body
The definition of a lean body is often subjective and judged by the beholder. However, there are concrete numerical ranges for body composition, or fat-to-lean mass, that are optimal for health. Guidelines for what constitute optimal lean body mass are based on relative levels of fat, and as such will differ between groups of people such as men and women. They also differ based on age and health status.
According to guidelines from the National Institutes of Health, women should have a body fat of 20 to 21 percent, meaning that the rest of their body composition will be lean tissue — organs, muscle, bone — and water. A woman with more than 30 percent body fat is considered obese. The recommended body fat for men is 13 to 16 percent, with 25 percent or higher classified as obese.
Measuring Lean Tissue
Muscle Mass & BMI
Lean tissue can be measured with a variety of devices, which range in technique, accuracy, cost and ease of use. Scales that use bioelectric impedence analysis (BIA), a small electric current that measures fat and lean tissue, can be purchased for home use. Calipers can also be purchased, but should be used by a trained professional. Advanced techniques which are more accurate and costly include underwater weighing and dual energy X-ray absorptiometry (DEXA), a scan that can measure muscle, fat and bone density.
- Lean tissue can be measured with a variety of devices, which range in technique, accuracy, cost and ease of use.
- Scales that use bioelectric impedence analysis (BIA), a small electric current that measures fat and lean tissue, can be purchased for home use.
Benefits of a Lean Body
Having enough lean body mass to fall under the recommended fat levels reduces the risks for health problems such as high blood pressure, high cholesterol and diabetes, according to the American Heart Association. The Centers for Disease Control recommend changes to diet and increased exercise as a means to increase lean body mass.
Lean Body Misconceptions
What Is Normal Body Fat?
The definition of a lean body is not necessarily a body devoid of fat. Certain groups of people, such as athletes and trained bodybuilders, will have very low body-fat levels and high lean-tissue mass, but this is not ideal for everyone. Some fat is essential for vital bodily functions such as energy storage and organ insulation, and most Americans fall at or above the recommended fat ranges.
Muscle Mass & BMI
What Is Normal Body Fat?
Body Frame & Ideal Body Weight
How Much Should a 5'11 Male Weigh?
The Ideal Body Fat Percentage
What Body Type Am I if I Gain & Lose Weight Easily?
How Much Should a Woman Who Is 5'8 Weigh?
Healthy Body Fat Percentage Loss
Normal Weight for a 5'4" Girl
How Much More Muscle Mass Does a Male Have Than a Female?
- American Heart Association: Body Composition Tests
- Centers for Disease Control: Physical Activity and Health
- Lee SY, Gallagher D. Assessment methods in human body composition. Curr Opin Clin Nutr Metab Care. 2008;11(5):566-72. doi:10.1097/MCO.0b013e32830b5f23
- St-onge MP, Gallagher D. Body composition changes with aging: the cause or the result of alterations in metabolic rate and macronutrient oxidation?. Nutrition. 2010;26(2):152-5. doi:10.1016/j.nut.2009.07.004
- Clark JE. Erratum to: Diet, exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18-65 years old) who are overfat, or obese; systematic review and meta-analysis. J Diabetes Metab Disord. 2015;14:73. doi:10.1186/s40200-015-0154-1
- American Academy of Orthopaedic Surgeons. Female Athlete Triad: Problems Caused by Extreme Exercise and Dieting. http://orthoinfo.aaos.org/topic.cfm?topic=A00342.
- American Council on Exercise. Tools and Calculators. https://www.acefitness.org/acefit/healthy_living_tools_content.aspx?id=2
- Fahey TD. Fit & Well: Core Concepts and Labs in Physical Fitness and Wellness. New York: McGraw-Hill Education; 2017.
- National Heart, Lung, and Blood Institute. Assessing Your Weight and Health Risk. https://www.nhlbi.nih.gov/health/educational/lose_wt/risk.htm.
Pha Lo has received fellowships from the American Society of Newspaper Editors and the California Women's Foundation. Her work has been published in the "San Francisco Chronicle," "Sacramento Bee," "Pacific News Service" and "Audrey Magazine." She graduated from the University of California at Berkeley with a Bachelor of Arts in political science. Lo is a nutrition educator and a certified food safety manager.