Measuring Overweight and Obesity

Are You Pleasingly Plump or Overweight?

Most people and healthcare providers used to determine their weight status by standing on a scale and comparing their resulting weight with standardized height and weight charts That had been developed using data collected by the Metropolitan Life Insurance Company.

The Problem with Height and Weight Tables

There were two key problems with the data collected for these charts. First of all, it was not colleted scientifically. It was derived from the height and weight information collected from people who applied for insurance instead of from a sample of the entire US population. Secondly, simply correlating weight with height does not account for genetic differences in body build, which can influence bone size and density. Consequently, these outdated charts misclassified people with very small or very large frames as underweight or overweight, respectively.

In the past 30 years, medical investigators have learned a lot about overweight, obesity and the health risks associated with these conditions. They have also developed additional tools with which to assess the amount of adipose (fat) tissue a person is carrying.

Since 1998, the National Institutes of Health has advocated that people use the Body Mass Index (BMI) chart instead of the height and weight chart to determine if they are overweight and if the amount of fat they are carrying puts them at risk for health problems.

What is BMI?

BMI is the ratio of a person’s weight in kilograms to their height in meters squared. This ratio is a much more accurate way to identify how much of a person’s body weight is due to adipose than height and weight comparisons. Health risks increase when BMI exceeds 25 and falls below 18.

Still, BMI is not a perfect tool. It tends to overestimate body fat content in very muscular athletes and in African Americans since they tend to have heavier skeletons than Caucasians. By contrast, it often underestimates body fat content in Asians since their skeletons tend to be less dense than Caucasians.

BMI’s value as a diagnostic tool can be improved by paring it with other measurements such as waist circumference.

Why Emphasize Waist Circumference?

Researchers have found that a person’s body fat distribution pattern is just as important as his/her body weight or percent body fat in assessing weight-related health risks. Simply put, overweight and obese people have two basic fat distribution patterns:

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This typically male pattern of fat distribution results in a large, apple-shaped abdomen. This pot-bellied appearance is favored by male sex hormones and is associated with a higher incidence of heart disease, hypertension, type 2 diabetes, and metabolic syndrome. Some studies have suggested that women with this pattern of fat accumulation also tend to be at greater risk of developing breast cancer.

Gynoid or Gynicoid

This typically female pattern of fat distribution results in large hips, buttocks, and thighs but in a small abdomen. The female sex hormone progesterone favors storage of fat in the lower area of the body. Lower body fat does not appear to increase the risk of heart disease, diabetes, or hypertension, but it does seem to be harder to lose weight in this area through diet and exercise than it is to lose abdominal fat with those traditional weight loss options.

During the 1990s, measuring hip and waist circumference and taking a ratio of these measurements was a popular diagnostic tool for assessing heart disease risk. Within the past two years, however, numerous large-scale studies, one of which involved over 27,000 people in 52 countries around the world, have shown that measuring waist circumference (WC) by placing a tape measure just above the umbilicus is often a more accurate method for predicting weight-related disease risk.

Since 2003, the American Association of Family Physicians has advocated BMI and WC measurements be obtained as part of all patients’ routine vital signs screening and that this information be used to discuss weight management’s role in good health, regardless of patients’ current BMI and WC.

Based on current research, men who have a WC greater than 40 inches and women who have a WC greater than 35 inches are at higher risk of diabetes, dyslipidemia (high blood fat levels), hypertension, and cardiovascular disease because of excess abdominal fat than individuals with trimmer waists. Individuals with a WC greater than these values should be considered one risk category above that defined by their BMI.