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Body Fat Percentage vs. Body Mass Index

Updated: May 14

man running on treadmill

Maintaining a healthy weight is important for overall well-being, but it can be challenging to determine what "healthy" means. The truth is that the number on the scale does not paint a full picture of a person’s health. As you know, two people can be the same exact weight but look different due to body type. Usually when people say “I want to lose weight”, they really mean that they want to change their overall body composition. Body composition is a term used by health professionals to refer to the percentages of muscle, fat, and bone in your body. It is a more accurate representation of the health of your body. Two common measurements used to assess weight are body fat percentage and body mass index (BMI). While both are useful, they differ in what they measure and their accuracy in assessing overall health.

Body Fat Percentage:

Body fat percentage measures the amount of fat in your body relative to your total body weight. Our bodies use fat and store it as energy for later use. More importantly, according to Harvard Health, it helps give your body energy, protects organs, supports cell growth, and helps your body absorb vital nutrients. Nevertheless, many health issues arise when there is an excess of body fat in the body. This can lead to heart disease, high blood pressure, and diabetes. This measurement takes into account both essential fat or brown fat (the fat necessary for basic bodily functions) and non-essential fat or white fat (the fat that accumulates under the skin and around organs). The American Council on Exercise (ACE) provides the following body fat percentage categories:

Essential fat: Men: 2-5%, Women: 10-13%

Athletes: Men: 6-13%, Women: 14-20%

Fitness: Men: 14-17%, Women: 21-24%

Acceptable: Men: 18-24%, Women: 25-31%

Obese: Men: 25%+, Women: 32%+

Body Mass Index:

BMI, on the other hand, is a measurement of body weight relative to height. It is calculated by dividing weight in kilograms by height in meters squared. The World Health Organization (WHO) provides the following BMI categories:

Underweight: BMI < 18.5

Normal weight: BMI 18.5-24.9

Overweight: BMI 25-29.9

Obesity class 1: BMI 30-34.9

Obesity class 2: BMI 35-39.9

Obesity class 3: BMI 40+

BF% vs. BMI:

While BMI is an easy and cost-effective way to assess weight, it has limitations. It does not differentiate between fat and muscle, meaning that someone with a high amount of muscle mass may have a high BMI but a low body fat percentage. Similarly, an elderly person or someone with a health condition that causes muscle loss may have a low BMI but a high body fat percentage.

Body fat percentage, on the other hand, provides a more accurate assessment of body composition. However, it can be difficult to measure accurately, as methods such as skinfold calipers and bioelectrical impedance analysis can be influenced by factors such as hydration levels and the time of day. There are many ways to measure body fat and each has its own level of reliability and accuracy.


The weight scale doesn’t always paint the full picture of health. Actually, sometimes actual pictures are the best method for tracking progress. Both body fat percentage and BMI are useful measurements for assessing weight and offering a quick glimpse at what an individual’s health could be. While BMI is easy to calculate, it has limitations in that it does not differentiate between fat and muscle. Body fat percentage provides a more accurate assessment of body composition, but can be difficult to measure accurately. Body fat percentage may be a more accurate assessment of overall health. Ultimately, it is important to use these measurements as tools rather than the sole determinants of health and to consult with a healthcare professional for personalized advice.

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