The number of overweight and obese individuals has reached epidemic proportions worldwide, according to the World Health Organization. Obesity poses health risks including type 2 diabetes, heart disease, stroke and some types of cancer. There are several methods to help assess body fat, body-fat distribution, weight and chronic disease risk. These include BMI--or body mass index--waist circumference and waist-to-hip ratio.
BMI
BMI is used as a guide to help determine if an individual’s weight in relation to height is in a healthy range. BMI is also a reliable estimate of body fat in most cases--exceptions include extremely muscular individuals or the elderly. Those with BMIs below 18.5 are considered underweight; BMIs of 18.5 to 24.9 are healthy weights; BMIs of 25.0 to 29.9 are overweight; and BMIs of 30.0 and above are considered obese.
Determining BMI
The method for determining BMI is the same for men and women. According to the American Dietetic Association, BMIs can be determined using the following formula: weight in pounds times 703, divided by height in inches, divided by height in inches again. For example, a person who is 5 feet 5 inches tall and weighs 160 lbs. has a BMI of: 160 Ibs. times 703, divided by 65 inches, divided by 65 inches, which equals 26.6 and would be in the overweight category. The American Dietetic Association provides a useful adult BMI calculator on its website.
Waist-to-Hip Ratio
Waist-to-hip ratio is another tool used along with BMI to help assess weight status, body fat and disease risk. People with more fat accumulation around the waist typically have an increased disease risk.
Measurements for waist-to-hip ratios are performed by placing a tape measure around the waist and hips. Waist measurements should be taken at the narrowest point of the waist and hip measurements at the widest point around the hips. The waist-to-hip ratio is determined by dividing the waist measurement--in inches--by the hip measurement--in inches. According to AIDS InfoNet, waist-to-hip ratios below .8 for women and below .9 for men are considered healthy measurements.
Expert Insight
Compared to waist-to-hip ratio, waist circumference is a quicker and easier method for assessing body fat and disease risk. According to the National Heart, Lung, and Blood Institute, waist-to-hip ratios have no advantage as assessment tools compared to waist circumference alone.
A 2003 study published in the monthly journal of the Association of Physicians found that although waist circumference and waist-to-hip ratio were both good measures of subcutaneous abdominal fat tissue, waist circumference was the strongest predictor of distribution of fat tissue in several abdominal fat compartments in men.
Waist Circumference
Waist circumference can be used in place of waist-to-hip ratio since it's a quicker and easier assessment method and a strong indicator of adipose tissue and disease risk. Even if BMI falls within a normal range, a high waist circumference can put an individual at risk for disease.
Waist measurements should be taken around the smallest part of the waist just above the hip bone. According to the Weight-control Information Network, individuals with waist measurements of more than 35 inches for women and more than 40 inches for men have an increased risk for disease due to a higher percentage of abdominal fat.
References
- World Health Organization: Obesity and overweight
- American Dietetic Association: What’s Your Number?
- National Heart, Lung, and Blood Institute: Identification, Evaluation and Treatment of Overweight and Obesity in Adults.
- AIDS InfoNet: Body Composition Tests
- "Monthly Journal of the Association of Physicians"; Waist circumference, waist-to-hip ratio and body mass index as predictors of adipose tissue compartments in men; DC chan et al.; June 2003
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