April 2004

Federation of American Societies for Experimental Biology

Obesity alone not a good predictor of cardiovascular risk and death, fat distribution proved best

The most frequent cause of death for obese people is cardiovascular. But in a study of 17,234 men and women, obesity alone - especially severe obesity in women - was not a good predictor for cardiovascular risk. Cardiovascular deaths in women rose as obesity increased, then leveled off before the average weight was even 200 pounds. However, death rates for men continued to climb as weight went up. Body shape - whether fat was distributed on the abdomen or on the thighs and hips - proved a better predictor.

The new study by University of Texas Southwestern researcher Edward Harry Livingston was presented at Experimental Biology 2004 as part of The American Physiological Society's scientific sessions.

Dr. Livingston, a surgeon who performs bariatric surgery for the extremely obese, says obesity clearly causes diabetes and hypertension, which in turn cause cardiovascular diseases. Yet, he points out, several large studies have failed to show that obesity and mortality are clearly related. For that reason, he used data from the NHIS and NHANES III surveys to determine the relationships between obesity, cardiovascular mortality, and individual cardiovascular risk factors such as cholesterol, triglycerides, blood sugar, and blood pressure. He also looked at body shape as defined by circumference of waists and thighs.

Death from cardiovascular disease increased steadily for women once they passed a body mass index of 25 (approximately 160 lbs. for a 5'6" woman) until they reached body mass index of 30 (approximately 185 lbs.), then it leveled off. Based on obesity alone, a woman was no more likely to die at a body mass index of 50 (approximately 310 lbs.) than at 35. For men, death from cardiovascular death continued to climb as body mass index climbed. Only blood pressure, both diastolic and systolic, increased in anything resembling a similar pattern.

The worst combination of cardiovascular risk factors, irrespective of weight, was found in people with large waists and narrow thighs. Seriously obese individuals without this body type had a better cardiovascular risk profile than individuals with this body type who were smaller.

Dr. Livingston says these findings do NOT indicate that being obese is without risk, as the elevated death rates indicate. But the findings do call into question whether moving from one level of overweight/obesity to a higher one always increases the risk of dying from heart disease. The findings also reinforce the importance of body shape. Some very obese individuals appear to have the ability to store fat in their lower bodies without causing an increase in cholesterol as occurs in those who store fat in their abdomen, allowing them to become massively obese without a corresponding rise in cardiovascular risks.

This article comes from Science Blog. Copyright 2004