What is body mass index (BMI)?

One of the most common topics patients address with their doctors is their weight. Some patients weigh too little, but others feel they weigh too much. Genetic, socioeconomic and physiological factors all contribute to a person’s weight.

There are several ways to measure a person's weight. The most common screening tool is the body mass index (BMI). The BMI is a number calculated from a person's weight and height. In most people, BMI relates with body fat. It is not accurate in some cases.

The chart can help you determine your BMI. The figure at which your height matches your weight is your BMI. BMI is classified as the following:

  • BMI under 18.5 is underweight.
  • BMI 18.5 to 24.9 is typically healthy weight.
  • BMI 25.0 to 29.9 may indicate overweight status.
  • BMI 30.0 to 39.9 may indicate obesity.

*The BMI as a screening tool has limitations depending on how much muscle a person has. Muscle is denser than fat, so BMI may overestimate body fat.

Body Mass Index chart

Does being overweight lead to any medical risks?

The best reason to attain and maintain your ideal weight is to reduce or eliminate medical problems that are more likely to occur with increasing weight. These conditions include high blood pressure, coronary artery disease, type 2 diabetes, cardiovascular disease, cancer, and other medical problems. All of these conditions contribute to an overall increase in mortality (rate of death).

A person with a BMI of greater than 30 may have high risk for diabetes, high blood pressure and heart disease. A low BMI may lead to other medical problems like malnutrition, body image issues and poor bone density.

Are treatment plans available to help me lose weight?

Yes, there are treatment plans to help with weight loss. A healthy diet and/or exercise may help you reach a healthy weight. Your doctor and your dietitian can help you plan to make changes.

What steps should I take to help me lose weight?

  • Decide you want to permanently lose weight.
  • Seek professional help from your doctor and a registered dietitian.
  • Educate yourself.
  • Have a realistic goal in mind.
  • Follow up with your care team for support.
  • Understand that obesity is a long-term condition and it will require life-long attention.

What is the healthy range of body fat?

Healthy body fat ranges are different for men and women. High body fat may lead to heart disease, stroke and diabetes. Low body fat may be related to malnutrition. Just the right amount of body fat helps vitamins and minerals get in the body. It also helps maintain body temperature and offers protection to the organs. It also provides a source of energy for the body.

Age
(years)

Healthy Range of
Body Fat for Females

Healthy Range of
Body Fat for Males
20-4021-33%8-19%
41-6023-35%11-22%

The chart is adapted by “Shape Up America!” from Gallagher D, et al. Am J Clin Nutr. 2000;72:694-701.

The amount of fat in the body can be measured. One method allows a weak current to run through the body. It runs through muscle, fat, water and bone at different levels and can estimate total body fat. A body fat analyzer measures the resistance the body gives off as this current flows through it.

Body fat percentage refers to the percentage of body fat mass (weight of the fat) in relation to body weight. The weight that is not fat is referred to as the fat-free or lean body mass. A change in diet and exercise may lead to less body fat and less risk for medical complications.

Last reviewed by a Cleveland Clinic medical professional on 09/18/2019.

References

  • World Health Organization. Obesity: Preventing and managing the global epidemic. In: Report of a WHO Consultation. Geneva, Switzerland: World Health Organization, 1998.
  • Nickerson BS, Esco MR, Bishop PA, et al. Validity of BMI based body fat equations in men and women: A four compartment model comparison. 2018;32(1):121-129.

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