Obesity

One of every two Americans is overweight, and one in five is obese.

There are various ways of determining whether you are overweight or obese — none of which is perfect. One of the easiest is to compare your weight with the recommended weights on the table from the federal government's "Dietary Guidelines for Americans." Another commonly used method is to calculate your body mass index or BMI.

But no height-weight table or BMI calculation can take into account individual variations in proportions of fat and lean tissue (since muscle weighs more than fat) or the distribution of fat in the body. For instance, a person with a great deal of muscle may be overweight according to the table or BMI calculator, but have a very low proportion of body fat and thus not be obese.

Where your body's weight is distributed also has an important bearing on your risk of cardiovascular disease. In some obese people, most of the excess fat is deposited in the abdomen (visceral fat) — they are called "apple-shaped" — while it settles around the hips and thighs in "pear-shaped" folks. Apple-shaped people (more commonly men) have a higher risk of heart disease than do those shaped like a pear (more commonly women). One possible reason: While other fat cells empty their fat content directly into the general blood circulation, the contents of abdominal fat cells go directly to the liver before entering the bloodstream. Abdominal obesity is associated with a resistance to insulin; in an effort to compensate for this resistance, the pancreas secretes excessive amounts of insulin. The resulting high blood levels of insulin set up a complex chain of reactions that eventually leads to hypertension, elevated triglycerides, low HDL levels and accelerated atherosclerosis; diabetes and coronary heart disease may follow.

One way to estimate your risk is to divide your waist circumference by your hip measurement. A ratio less than 0.80 is desirable for women, and a ratio less than 1.0 is desirable for men.

One way to help determine whether you have too much visceral fat is to divide your waist circumference by your hip measurement. A ratio greater than 0.80 for women or a ratio greater than 1.0 for men suggests excess visceral fat.