What Is Body Composition?

Body composition is a term used often by doctors and health professionals. It refers to the percentage of fat, bone, and muscle in your body. Doctors use body composition to see if you’re at a healthy weight for your individual body. 

Why Is Body Composition Important?

Body composition is a universal term used in the health and fitness industry. Doctors use body composition to find what percentage of your body weight is fat. This helps them find out your level of health. Body composition is important because someone else can be the same height and weight as you, but they might have more body fat and less muscle. This could lead to different health issues in them. 

The scale won’t tell you how much of your body is made up of fat and muscle mass. But assessing body composition can help you find that. Healthier body composition is less fat and more muscle mass. Too much body fat can lead to risks like cancer, diabetes, heart disease, and other health problems.

What Is Body Fat?

Your body is made up of water, protein, fat, and minerals. There are two types of fat in your body. 

Non-fat mass. This is also known as essential fat. This kind of fat is in your bones, liver, kidneys, intestines, and muscles. Fat in these places is required for your body to function normally. 

Fat mass. Also known as stored fat, this is found in your adipose tissue. This type of fat is used as energy for your body. It insulates and cushions your body. It surrounds your organs and is just under your skin. 

Excessive stored fat can be harmful to your health. Having too much stored fat can lead to chronic diseases and conditions.

These may include: 

Checking your body composition lets you know the shifts in your body fat and muscle mass. If you exercise less or more but your weight stays the same on the scale, your internal body composition could have changed. 

How Body Mass Index Is Different

When thinking about body composition, body mass index (BMI) might come to mind. But BMI doesn’t measure body fat. Doctors use BMI to find out your weight status. There’s a range of healthy to unhealthy BMIs. BMI only tells you the ratio of your weight to your height, however, so it's not an incredibly accurate tool to know if you’re at a healthy level or not. 

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Typically, a high BMI of more than 30 does indicate obesity. If you have a BMI of over 30, you may have a higher body fat percentage. This could put you at risk for health problems like hypertension (high blood pressure), osteoarthritis, stroke, or type 2 diabetes. 

Doctors use BMI to measure your height and weight, and to find if you are underweight, normal weight, overweight, or obese. BMI is associated with body fat percentage but doesn’t give an accurate picture of your body makeup. 

BMI is more helpful as a global index for nutrition. When used to help determine if a person is overweight, obese, or has an eating disorder, it can be useful. But if it’s used for body composition, it’s not as accurate or helpful.

Determining Body Composition

To find out what your body fat percentage is, a health professional might use skin calipers to measure your stored fat. However, there are other more accurate ways of measuring your body composition.

Skin calipers.  A health professional will use skin calipers to measure your skinfold thickness. They’ll measure areas where stored fat is commonly found. When done with a good technique, skin calipers can be very accurate. But human error can cause many fluctuations.

Underwater weighing. When underwater, your lean tissue sinks, and fat floats. Your underwater weight helps estimate how much fat mass you have. This is a very accurate method of finding body composition. But it requires special equipment. 

A body pod. This kind of machine measures how much air your body displaces. It’s a more convenient option compared to underwater weighing. It also takes less time. 

Dual x-ray absorptiometry (DEXA) scan. A DEXA scan uses low-level x-rays to find how much body fat, muscle, and bone are in your body. It's quick and also includes bone in the assessment.

Bioelectrical impedance. This analysis sends electrical currents through your body. It then measures the speed at which it travels. It’s the cheapest method of measuring your body fat, after skin calipers. However, the accuracy depends on a lot of factors. It’s best for monitoring changes in your body fat. 

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According to the American Journal of Clinical Nutrition, there are healthy body fat percentages based on your age. For people aged 20 to 39, women should aim for 21% to 32% of body fat. Men should have 8% to 19%. For people 40 to 59, women should fall between 23% to 33% and men should fall around 11% to 21%. If you’re aged 60 to 79, women should have 24% to 35% body fat and men should have 13% to 24%. 

Women naturally have a higher body fat percentage than men. Their body fat will also naturally increase as they age. 

WebMD Medical Reference Reviewed by Melinda Ratini, DO, MS on June 02, 2021

Sources

SOURCES:

Archives of Disease in Childhood: “Measure body composition.”

Beth Israel Lahey Health Winchester Hospital: “Your Body Fat Percentage: What Does It Mean?”

For Care Education and Research.org: “What is Body Composition? The Definition, Guide and Test.”

UC Davis Health: “Body Composition.”

University of Virginia: “Body Composition.”

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