Updated June 25, 2002

Obesity, Type 2 Diabetes, and Physical Activity
What's the Connection?

by Richard M. Weil, M.Ed., C.D.E.

It's no coincidence that the rate of Type 2 diabetes is rising as rapidly as the rate of obesity in the United States. The two are strongly related: The heavier people are, the more likely they are to develop diabetes. So strong is the connection between obesity and diabetes that a new word, "diabesity," has been coined by the medical community. (The first diabesity conference was held in Virginia in March 2001.)

It's also no coincidence that Type 2 diabetes and obesity are on the rise at a time when physical inactivity is commonplace. Currently, more than 70% of the U.S. population is physically inactive. People who are physically inactive tend to be heavier than people who are active, and they tend to have more diabetes too.

While the rises in obesity and Type 2 diabetes show no signs of slowing any time soon, research suggests that something can be done to increase the number of people who are physically active and to decrease the number who develop obesity and Type 2 diabetes. This article offers suggestions to help individuals make informed decisions about losing weight and becoming more physically active.

Overweight or obese

In 1960, 43% of American adults (ages 20-80) were overweight or obese. Today, that number is 55%, or 97 million adults. If the increase in overweight and obesity continues at the current rate, by the year 2020, 61%, or 103 million adults, will be overweight or obese.

Overweight refers to an excess of body weight compared with standards set by the National Institutes of Health and the National Heart, Lung, and Blood Institute (NHLBI). The excess weight may come from muscle, bone, fat, or body water.

Obesity refers specifically to having an abnormally high proportion of body fat. One can be overweight without being obese, but many people who are overweight are also obese. Of the 97 million adults in the United States who are overweight or obese, almost 40 million are obese.

The most up-to-date method of assessing whether a person is overweight or obese is to calculate his body-mass index (BMI). This is done by dividing body weight (in kilograms) by height (in meters) squared. (See the Adobe Acrobat PDF file "Body-Mass Index" for determining your BMI based on your weight in pounds and height in inches.) According to the NHLBI, normal weight is defined as a BMI less than 25 kg/m2, overweight as a BMI of 25-29.9 kg/m2, and obesity as a BMI of greater than or equal to 30 kg/m2.

Although BMI is simple and inexpensive to calculate and applies to both men and women (but not to children), it has some drawbacks. One problem is that it may misclassify individuals who are muscular. For example, a lean, muscular football player who is 5'11" and weighs 225 pounds has a BMI of 31.5 kg/m2. By definition, that puts him in the obese category, but he obviously isn't obese.

BMI is best used to help estimate your relative, weight-related risk of disease compared to normal weight. But since some people can be healthy even if their BMI is high, don't make assumptions about your health risk based solely on your BMI. Check with your doctor for other indicators of health risks such as high blood pressure, high blood sugar, low HDL cholesterol, and high total cholesterol, triglycerides, and LDL cholesterol. If your BMI is 25-29.9 kg/m2 and you don't have any risk factors, you probably don't need to lose any weight for health reasons.

Health risks of overweight

Richard Weil is an exercise physiologist and a consultant to the Naomi Berrie Diabetes Center at Columbia Presbyterian Medical Center in New York City.

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