Body Mass Index in Adults

The benefits of maintaining a healthy weight go far beyond improved energy and smaller clothing sizes. By losing weight or maintaining a healthy weight, you are also likely to enjoy these quality-of-life factors:

• Fewer joint and muscle pains
• More energy and greater ability to join in activities they enjoy
• Better control of bodily fluids and blood pressure
• Reduced burden on your heart and circulatory system
• Better sleep patterns
• Reductions in blood triglycerides, blood glucose and your risk of developing Type 2 diabetes
• Reduced risk for heart disease and certain cancers

What is BMI?

BMI is an indicator of the amount of body fat for most people. It is used as a screening tool to identify whether an adult is at a healthy weight.

• BMI is a numerical value of your weight in relation to your height. A BMI between 18.5 and 25 kg/m² indicates a normal weight. A BMI of less than 18.5 kg/m² is considered underweight. A BMI between 25 kg/m² and 29.9 kg/m² is considered overweight. A BMI of 30 kg/m² or higher is considered obese.
• To check your BMI, type your height and weight into the BMI calculator for adults from the National Institute of Health. A separate BMI percentile calculator should be used for children and teens that takes a child’s age and sex into consideration.
• To calculate your BMI manually, multiply your weight in pounds by 703, divide by your height in inches, then divide again by your height in inches.
• Waist circumference is the distance around your natural waist (at the iliac crest, or hip bone). If your BMI is between 25-35 kg/m², your goal for waist circumference is less than 40 inches if you're an adult man and less than 35 inches if you're a non-pregnant woman. 
• Some well-trained people with dense muscle mass may have a high BMI score but very little body fat. For them, the waist circumference, the skinfold thickness or more direct methods of measuring body fat may be more useful measurements than BMI. 

Excess weight increases the heart's work. It also raises blood pressure and blood cholesterol and triglyceride levels and lowers HDL (good) cholesterol levels. It can make diabetes more likely to develop, too.

Lifestyle changes that help you maintain a 3% to 5% weight loss are likely to result in clinically meaningful improvements in blood glucose and triglycerides and lower your risk of developing Type 2 diabetes. Greater weight loss (5% to 10%) can even help reduce blood pressure and improve blood cholesterol. 

Your body is made up of water, fat, protein, carbohydrates and various vitamins and minerals. If you have too much fat — especially if a lot of it is at your waist — you're at higher risk for health problems such as high blood pressure, high blood cholesterol and diabetes. That increases your risk for heart diseases and stroke. 

To determine your risk, find your height in feet and inches in the first column of the following table. The ranges of weight that correspond to minimal risk, moderate risk (overweight) and high risk (obese) are shown in the three columns for each height.

Obesity is a major, independent risk factor for heart disease. If you're overweight or obese, you can reduce your risk for heart disease by losing weight and keeping it off.

_{(Adapted from Obesity Education Initiative: Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, Obesity Research 1998, 6 Suppl 2:51S-209S)}