Fat is not bad, just misunderstood.

• Position: Research on body fat as health factor - Special Newsletter Edition: Your Health

Purdue University researchers have developed an unusual theory about obesity that says percentage of body fat is not itself a health risk. They maintain that it is the ability of the fat cells to remove harmful substances from the blood, not the amount of body fat, that determines a person's health risk. What this means for most people is that a varied, lowfat diet coupled with adequate exercise likely will allow the fat cells to function properly, even in overweight individuals.

Body fat cells, known as adipose tissue, remove substances such as glucose, lipids and triglycerides (also known as fatty acids), and cholesterol from the bloodstream that can be harmful when they are present in high concentrations. It is the excess of these substances, not the amount of fat a person has, that causes diseases.

Under ideal circumstances, the fat cells act as "buffers," taking in the substances during periods of excess and releasing them into the bloodstream when the body needs more. If the body produces too much of these substances, however, the fat cells become saturated and lose their ability to remove them from the bloodstream. Because a diet high in fat causes the body to produce more of the compounds, it is the most common reason fat cells become saturated.

R. Paul Abernathy, professor of foods and nutrition, points out that there currently is no adequate method to determine the fullness of someone's adipose tissue. Two indicators, though, are blood glucose and blood pressure levels. If...