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Estimating Body Fat Percentage and Lean Body Mass

When determining the body composition, experts distinguish between two types of body fat: essential fat and storage fat. Essential fat is necessary for normal functioning of the body, for example for providing important metabolic fuel for energy production. This type of fat includes fat in the heart, liver, kidneys, intestines, lungs, muscles, marrow of the bones, spleen as well as the brain and the spinal cord. It is higher in women than men due to gender-characteristic fat reserves needed for child-bearing (e.g. fat in the mammary glands and pelvic region).

Storage fat includes the fat that accumulates in adipose tissue to protect the body from injury and cold. This type of fat is located around internal organs and right beneath the skin. Storage fat does not include blood lipids (cholesterol and triglycerides), which are needed for transporting fat-soluble vitamins.

Lean Body Weight

The body’s fat-free component, on the other hand, represents the lean body mass, which includes the total weight of water, bones, muscles, tendons, ligaments and internal organs, excluding the essential fat found in the internal organs and bone marrow. When calculating an individual’s fat-free mass, the amount of essential fat is estimated and then subtracted along with storage fat from the person’s actual weight. There are several formulae, you can use, which were designed to simplify the process of estimating the lean body weight, such as the Hume formula:

Lean Body Weight (men) = 0.32810 × Weight in kilograms + 0.33929 × Height in centimetres – 29.5336

Lean Body Weight (women) = 0.29569 × Weight in kilograms + 0.41813 × Height in centimetres – 43.2933

You can also use this calculator which employs the above formula to estimate your lean body mass:

Or alternatively, you may try the James formula, which typically gives slightly higher results for lean body weight:

Lean Body Weight (men) = (1.1 × Weight in kilograms) – 128 × (Weight in kilograms ^ 2/Height in centimetres ^ 2)

Lean Body Weight (women) = (1.07 × Weight in kilograms) – 148 × (Weight in kilograms ^ 2/Height in centimetres ^ 2)

When you know your lean body mass, then you also know the weight of your body fat, which is your actual body weight less your lean body weight as calculated above, and so you can easily calculate your percentage of body fat (read on to learn more about how to calculate the body fat percentage using different other methods).

A person’s body composition should contain the proper balance between the fat and fat-free component. Excessive body fat is known to present serious health risks, including cardiovascular disease, hypertension, diabetes, gallbladder disease, joint problems and respiratory dysfunction. Studies show that fat which accumulates around the waist creating an “apple-shaped” body (more common in men) tends to present greater health risks than fat around the thighs and buttocks creating a “pear-shaped” body (more common in women). This puts men at greater risk of developing the aforementioned health problems.

However, being too thin also poses potential health risks. People who do not consume enough calories may not have the energy needed to maintain good health and may be at an increased risk for conditions such as menstrual problems, infertility, increased vulnerability to infections and osteoporosis and may also be less able to preserve underlying tissue when battling cancer.

Normal-weight body fat composition falls between 13% and 21% for men, and 23% and 31% for women. Health problems are more likely to begin when body fat exceeds 22% in young men and 25% in men over 40. Women are at an increased risk of developing health problems when their body fat exceeds 32% (young women) and 35% (those over 40 years of age). In contrast, normal body functions may be endangered if body fat falls below 5% for men and 15% for women. However, some people may need higher levels of body fat. For instance, a pregnant woman may need more body fat to help ensure the healthy growth of the fetus. Likewise, a person who works outdoors in cold-weather may also benefit from slightly higher levels of body fat.

As people age their fat content changes and so does their body composition. After age twenty, people tend to gain between one and three percent of body fat per decade up to the age of sixty. Bone mass may also decrease by about three percent per decade after about age thirty-five. Therefore, people who weigh the same amount at age sixty as they did at age twenty may in fact have significantly higher stores of body fat than they did when they were young.

Measuring Body Fat

When monitoring a person’s weight and body composition, health care professionals often use one or more of three basic measurements, including the body mass index (BMI), waist-to-hip ratio and waist-to-height ratio. Other sophisticated tests of body composition that are not commonly available and are only performed in specialized facilities have been described in our previous post where you can also calculate your BMI.

Body Fat Calculation Using Waist-to-Hip Ratio

As it was mentioned earlier, having excess fat around the waist poses greater risk of developing health complications than carrying excess weight around the hips. Waist-to-hip ratio is therefore a simple but very useful tool for assessing potential health risks associated with excess weight. You can try the waist-to-hip ratio calculator below to assess your own health risks. Make sure to measure your waist circumference at your bellybutton (at the narrowest point) and your hip circumference at the widest point.

Body Fat Calculation Using Waist-to-Height Ratio

Waist-to-height ratio is yet another simple indicator of a person’s health risks associated with excess body weight. A waist-to-height ratio above 49% for women and 53% for men is indicative of an increased risk of health complications. You can use the waist-to-height calculator below to check your own risks.

Body Fat Calculator Using Wrist, Waist, Hip and Forearm Circumference

There is yet another commonly used approach to estimating the body fat percentage based on formulae that are largely different for men and women. The formula for men estimates the body fat percentage on the basis of a person’s weight and waist circumference whereas the formula for women is much more complex, using also factors such as wrist, hips and forearm circumferences in addition to weight and waist circumference. The respective formulae are as follows:

Body fat percentage (men) = (Weight in pounds – (94.42 + Weight in pounds × 1.082) + (Waist Circumference in inches × 4.15))/Weight in pounds

Body fat percentage (women) = (Weight in pounds – (8.987 + Weight in pounds × 0.732) – (Wrist Circumference in inches/3.14) + (Waist Circumference in inches × 0.157) + (Hip Circumference in inches × 0.249) – (Forearm Circumference in inches × 0.434))/Weight in pounds

The following body fat calculator can do all that work for you:

See also: Calculating the Basal Metabolic Rate (BMR) and Calculating the Body Adiposity Index (BAI)