According to a recent poll, about 60 percent of overweight people don’t realize they need to lose weight. Other researchers found that 85 percent of obese people don’t recognize that they are so. So how can you determine whether you’re in either category?
The most accurate way to determine whether you are overweight is to measure the amount of body fat you have. Because this is not easy, doctors typically rely on surrogate measures, such as body mass index (BMI) and waist circumference, to determine who needs to lose weight.
Height/weight tables are the most straightforward way to assess your weight, but they are not the best method. The tables are not based on scientific calculations of ideal weight. Instead, they were derived from the height, weight and mortality data of people seeking life insurance. Moreover, they do not take into account your body composition. For these reasons, height/weight tables are rarely used.
Body mass index (BMI)
The standard method to determine whether you are overweight or obese is to calculate your BMI, a measurement of your weight as it relates to your height. It correlates strongly with the amount of body fat you have, although it does not measure body fat directly. National guidelines define overweight as a BMI of 25 to 29.9 and obesity as a BMI of 30 or greater. Extreme morbid obesity is a BMI of 40 or greater.
BMI is calculated by multiplying your weight in pounds by 703, then dividing the result by the square of your height in inches. For example, if you are 140 pounds and 5 feet 4 inches tall, multiply 140 × 703 (which equals 98,420). Then divide this number by 64 inches squared, or 4,096 (98,420 ÷ 4,096). In this case, your BMI is 24.
While BMI is a general assessment of body weight and disease risk, waist circumference provides a more specific indication of health risk because it measures harmful abdominal fat. Research shows that death rates from and risks of diabetes, high blood pressure and heart disease are substantially higher in those with a disproportionate amount of body fat stored in the abdomen—and evidence is accumulating that waist circumference is a better predictor of these risks than BMI.
Even in people who are of normal weight, an increased waist circumference may be linked to an elevated health risk. In addition, in men and women who are overweight or obese, a large waist circumference increases the already elevated risk of disease. Fortunately, abdominal fat is often the first to go when you lose weight.
To determine your waist circumference, wrap a tape measure around your waist at the top of your hip bones until the tape feels snug without compressing your skin. Then, exhale normally and take the measurement. A waist circumference greater than 40 inches in men or 35 inches in women indicates abdominal obesity.
Abdominal obesity is particularly dangerous because it can make the body resistant to the actions of insulin, a hormone that regulates blood glucose levels. Belly fat is associated with inflammation throughout the body, which is believed to contribute to insulin resistance as well as cardiovascular disease.
Insulin resistance is associated with a condition called metabolic syndrome, which significantly increases the risk of diabetes, heart attacks and strokes. People with metabolic syndrome have three or more of the following risk factors: a large waist circumference (abdominal obesity), high blood glucose or triglyceride levels, a low high-density lipoprotein (HDL) cholesterol level and high blood pressure.
Men are more likely than women to deposit fat in the abdomen—developing what’s commonly called a potbelly, beer belly or apple shape. Women tend to accumulate fat around the hips, buttocks and thighs, a distribution called a pear shape. Nevertheless, women are not immune to accumulating abdominal fat.