Also indexed as: BMI, Body Mass Index, Weight (Ideal)
People are often concerned about their weight because fashion trends and celebrities’
physical appearances influence popular body-image ideals—but these ideals do not
necessarily represent healthy weight ranges.
Since people usually increase their body fat when they gain weight, overweight often leads
to health risks.1 However, not all weight gain represents excessive fat. Weight
gain in bodybuilders, for example, is due to increases in muscle that is part of the
body’s lean mass, and there is no evidence that increased lean body mass is unhealthful.
Similarly, weight gain during pregnancy is a natural and essential process for supporting
fetal growth. Health concerns about overweight are actually concerns about the effects of
excess body fat on disease or the risk of disease.2
How do I know if my weight is affecting my health?
In 1998, a report containing the conclusions of a panel of health experts set guidelines
for deciding when excess weight should be considered a health risk.3 They
determined that three pieces of information were needed to decide whether weight loss should
be recommended to improve current and future health:
Body weight compared to height
Health professionals currently use the Body Mass Index (BMI) to estimate the health risks
associated with being overweight or underweight. BMI is calculated by one of the following
- BMI = weight in kilograms/(height in meters squared)
- BMI = [weight in pounds/(height in inches squared )] x 703
Body Mass Index chart
You can also obtain a simple measurement of BMI using following chart. Find your height in the
left-hand column, then follow the bottom row to the right until you reach your weight. From
left to right, the four chart areas show the ranges of low, normal, high, and very-high
Body Mass Index values
The Body Mass Index is only one tool for assessing health risks associated with weight. To
learn more, read this full article and see a health professional for a more precise
- 18.5 or less: Low BMI (underweight)
- 18.5 to 24.9: Medium BMI (normal weight)
- 25 to 29.9: High BMI (overweight)
- 30 and above: Very-High BMI (obese)
Note: For a very muscular person, a high BMI does not necessarily indicate
overweight, since the extra weight might be muscle, rather than fat.
Abdominal fat has been recognized as the type of fat leading to the highest health risks
compared with fat located elsewhere in the body. Waist circumference is considered a good
indication of the amount of abdominal fat a person is carrying.
To measure waist circumference, the top of the upper-right hip bone (known as the iliac
crest) is marked and a measuring tape is passed around the abdomen at this level. The tape
should be snug but should not compress the skin, and the waist circumference measurement
should be made at the end of a normal breath following exhalation.
Presence or risk of weight-related disease
People with weight-related diseases such as cardiovascular disease, and those who have high
risk for those diseases, may need to lose weight, even if they are only moderately overweight,
in order to promote optimal health.
If you have been told you have coronary heart disease, symptomatic carotid artery disease,
peripheral arterial disease, abdominal aortic aneurysm, type 2 diabetes, or sleep apnea, you
are in the high-health-risk category for the purpose of determining whether you should lose
weight. You are also in this category if you have any two or more of the following heart
disease risk factors:
- You are a male aged at least 45 years.
- You are a female aged at least 55 years or you are a postmenopausal woman.
- One or more members of your immediate family (parents or siblings) had premature severe
heart disease. Premature means before age 55 in a male relative or before age 65 in a female
relative. Severe heart disease means either a heart attack or sudden death assumed to be
- You are a cigarette smoker.
- You have been told you have high blood pressure or you are taking antihypertensive
- You have high blood levels of LDL (low density lipoprotein or “bad”)
- You have low blood levels of HDL (high density lipoprotein or “good”)
- You have high blood levels of glucose (elevated fasting glucose).
Some less serious diseases are also related to excess weight, and overweight people with
these diseases are usually advised to lose weight. These diseases include gallbladder disease,
osteoarthritis, stress incontinence, and gynecological problems such as excessive menstrual
bleeding (menorrhagia) and loss of menstrual periods (amenorrhea). Consult your healthcare
provider to find out whether any other health problem you have is related to excess
Who should lose weight to improve their health?
According to the report of the expert panel in 1998, people should lose weight if they fit any
of the following descriptions using the above measures of weight, waist circumference, and
- A BMI of 30 or above
- A BMI of 25 or above in people with existing cardiovascular disease or other diseases
associated with excess weight
- A BMI of 25 or above in people with two or more heart disease risk factors
- High-waist circumference (greater than 35 inches (88 cm) in women or 40 inches (102 cm) in
men) in people with existing cardiovascular disease or other diseases associated with excess
- High-waist circumference (greater than 35 inches (88 cm) in women or 40 inches (102 cm) in
men) in people with two or more heart disease risk factors
Are there other ways for measuring excess
weight or excess body fat?
Height-weight charts such as those published by the Metropolitan Life Insurance Company
were once popular for determining appropriate body weight. However, these charts have been
criticized because they were based on risk of death rather than disease, and because they were
not representative of the entire population of men and women.4
Since health concerns about overweight are actually concerns about the effects of excess
body fat on disease or the risk of disease, it could be useful to measure body fat directly.
Several methods for measuring body fat are available in health clinics, fitness centers,
college athletic departments, and other facilities. All of the following can be reliable for
estimating body fat if the person performing the measurement is well-trained and if the
equipment is of good quality and in optimum working condition:5 6
- Measurements of fat under the skin. These are done with skinfold calipers, or
infrared or ultrasound devices. Several measurements must be taken at different locations on
the body for the best accuracy.
- Measurements of whole body size and density. The most common methods used are
underwater (“hydrostatic”) weighing and air-displacement plethysmography (e.g.,
the “BOD POD”).
- Bioelectric impedance analysis. In this method a low-grade, imperceptible
electrical current is sent through the body, and changes in this current are measured and used
to calculate lean body mass and body fat. Methods that measure current from wrist to foot are
considered more accurate that those that measure current between both hands or both feet.
Although the above methods are considered potentially reliable for estimating body fat, no
well-researched guidelines exist for determining what levels of body fat are detrimental to
health, and there is no agreement about how to use these measurements to decide when weight
loss should be recommended.7 8 Excessive percentage body fat has been
suggested to begin at 21 to 25% for men and 31 to 32% for women depending on the
authority,9 10 11 but more research is needed to confirm
Is focusing on weight loss the best way to address the health
risks of excess weight?
Some authorities believe that too much public health emphasis is placed on losing excessive
weight instead of focusing on the promotion of a healthy lifestyle, including diet, exercise
habits, and other behaviors that reduce the risk of disease.12 13
14 They point out that not all obese people have increased health risks,15
and that weight-loss programs frequently fail in the long term, or result in only an
insignificant amount of weight loss.16 At the same time, healthy lifestyle changes
often result in a reduction in disease risk and other important health benefits, even if
weight change is not impressive. 17 18 19 20References:
1. Bray GA. Risks of obesity. Endocrinol Metab Clin North Am
2. Bray GA. Risks of obesity. Endocrinol Metab Clin North Am
3. National Heart, Lung, and Blood Institute. Clinical Guidelines on the
Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence
Report. NIH Publication No. 98-4083. Washington DC: National Institutes of Health, 1998.
4. McArdle WD, Katch FI, Katch VL. Sports and Exercise
Nutrition. Philadelphia: Lippincott Williams & Wilkins, 1999, 378.
5. Ellis KJ. Human body composition: in vivo methods. Physiol
Rev 2000;80:649–80 [review].
6. Fogelholm M, van Marken Lichtenbelt W. Comparison of body composition
methods: a literature analysis. Eur J Clin Nutr 1997;51:495–503 [review].
7. Svendsen OL. Should measurement of body composition influence therapy
for obesity? Acta Diabetol 2003;40 Suppl 1:S250–S253.
8. Prentice AM, Jebb SA. Beyond body mass index. Obes Rev
9. Heyward VH. Advanced Fitness Assessment and Exercise Prescription.
Champaign, IL: Human Kinetics, 1998.
10. Body Fat Content Chart for Women and Men. In software: NutriBase
Clinical Nutrition and Fitness Manager. Phoenix, AZ: CyberSoft, Inc., 2004.
11. Standing Committee on the Scientific Evaluation of Dietary Reference
Intakes, Food and Nutrition Board, Institute of Medicine. Dietary reference intakes for
energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids.
Washington DC: National Academy Press, 2002, 5–15.
12. Gaesser GA. Obesity, health, and metabolic fitness.
http://www.mesomorphosis.com/articles/gaesser/obesity.htm, accessed 5/10/2004.
13. Lyons P, Miller WC. Effective health promotion and clinical care for
large people. Med Sci Sports Exerc 1999;31:1141–6.
14. Miller WC, Jacob AV. The health at any size paradigm for obesity
treatment: the scientific evidence. Obes Rev 2001;2:37–45 [review].
15. Brochu M, Tchernof A, Dionne IJ, et al. What are the physical
characteristics associated with a normal metabolic profile despite a high level of obesity in
postmenopausal women? J Clin Endocrinol Metab 2001;86:1020–5.
16. NIH Technology Assessment Conference Panel. Methods for voluntary
weight loss and control. Ann Int Med 116: 942–949, 1992.
17. Gaesser GA. Thinness and weight loss: beneficial or detrimental to
longevity? Med Sci Sports Exerc 1999;31:1118–28 [review].
18. Tremblay A, Doucet E, Imbeault P, et al. Metabolic fitness in active
reduced-obese individuals. Obes Res 1999;7:556–63.
19. Tremblay A, Despres JP, Maheux J, et al. Normalization of the
metabolic profile in obese women by exercise and a low fat diet. Med Sci Sports Exerc
20. Appel, LJ, TJ Moore, E Obarzanek, et al. A clinical trial of the
effects of dietary patterns on blood pressure. N Engl J Med 336: 1117–24,