Body Composition and Body Fat Percent

How to measure and interpret your body fat percentage

Woman measuring percentage of body fat on waist
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Body composition is the proportion of fat and fat-free mass in your body. A healthy body composition is one that includes a lower percentage of body fat and a higher percentage of fat-free mass, which includes muscle, bones, and organs.

Body composition is measured to assess your health and fitness level. Often, you will have body composition measured at the start of a weight loss or fitness program and checked periodically to monitor your progress.

What Is Body Composition?

Your body is composed of two types of mass: body fat and fat-free mass.

  • Body fat can be found in muscle tissue, under the skin (subcutaneous fat), or around organs (visceral fat). Some fat is necessary for overall health. It is called essential fat and it helps protect internal organs, stores fuel for energy, and regulates important body hormones. But you may also have excess storage of fat and non-essential body fat.
  • Fat-free mass includes bone, water, muscle, organs, and tissues. It may also be called lean tissue. These tissues are metabolically active, burning calories for energy, while body fat is not.

Body fat percent is a measurement of body composition telling how much of the weight of your body is fat. The percentage of your body that is not fat is fat-free mass. There are normal ranges for body fat, which differ for men and women.

Weighing yourself on a regular bathroom scale does not truly assess your body composition because a regular scale cannot tell how much of your total weight is comprised of water, fat, or muscle.

To know if your body composition is healthy, you should get an estimate of your body fat percent.

Healthy Body Composition

The American Council on Exercise (ACE) gives these ranges of values for different populations:

ACE Body Fat Percent Norms for Men and Women

DescriptionWomenMen
Essential Fat10%  to 13%2% to 5%
Athletes14% to 20%6% to 13%
Fitness21% to 24%14% to 17%
Acceptable25% to 31%18% to 24%
Obeseover 32%over 25%

Athletes tend to have lower body fat, which may be beneficial for performance in sports such as running and cycling. But having an extremely low body fat percent is a health problem. The female athlete triad increases the risk of injury and health issues. It includes eating disorders, amenorrhea and decreased bone mass with an increased risk of stress fractures and osteoporosis.

If you are overweight or obese, you have an excessive amount of body fat and a high body fat percentage. You can improve your body composition by gaining lean body mass through building muscle and bones, and through losing excess body fat.

How to Measure Your Body Composition

There are several ways to get an estimate of your body fat percentage at home, at the gym, or from your doctor:

  • Bioelectrical Impedance: This is the method used by handheld units and by BIA body fat scales you step onto like a regular scale. A small electrical current passes through your body. Fat, water and lean tissue impede the current difference to give the reading. Many scales are sold for home use and no special training is required. Some scales, like the Fitbit Aria 2, even sync with your fitness tracker so that you can see how changes to your daily activity and diet affect your weight. 

  • Skinfold Measurements: This method is often used by fitness trainers or as part of a weight loss program. Calipers are used to take measurements at different parts of your body.

  • DEXA Scan (dual energy x-ray absorptiometry): This scan is performed in a medical setting and can also be used to check for bone density.
  • Hydrostatic Weighing: It's harder to find this gold standard for body fat measurement that involves being dunked in a water tank.
  • Body Fat Calculators: There are calculators that use various body measurements, including body mass index (BMI).

Factors Affecting Body Composition

Your body composition can be influenced by factors you can't control:

  • Age: People lose muscle mass as they age if they don't maintain it with sufficient weight training. This results in a slower metabolism.
  • Sex: Women have more body fat than men as nature's way of preparing for pregnancy and nursing.
  • Genes: These play a role in whether you are naturally lean or have a tendency to retain fat, including where you store it.
  • Hormones: These can influence water retention and body composition.

Should You Change Your Body Composition?

If your body fat percent is too high, you may want to try to decrease it to improve your health, athletic performance, and wellbeing. You may also be able to decrease your risk of disease. If your body fat percent is below the level of essential fat, you may also want to make changes to bring it up to that level as that will reduce your health risks.

To change your body composition for better health and fitness, aim to increase muscle mass and decrease excess fat mass. You can change your diet, start an exercise program, or combine both methods.

A Word From Verywell

Your body composition and body fat are important measurements when you are on a weight loss program. You could be successful in losing fat and gaining muscle without seeing your weight go down. Tracking your weight loss and fitness efforts with body composition measurement is a good way to see your progress. It is easier than ever with the wide availability of body fat scales.

Sources:

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.

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