Fat Sites Best Predict Heart Risk
Study: Obesity alone not best forecaster, especially in women
TUESDAY, April 20, 2004 (HealthDayNews) -- The amount of body fat you carry around does not predict heart disease as well as its location does, a new study claims.
The findings should call into question the practice of recommending bariatric surgery solely on obesity rather than other heart disease risk factors, Dr. Edward Harry Livingston, chairman of gastrointestinal and endocrine surgery at UT Southwestern Medical Center, said April 20 at the Experimental Biology 2004 meeting in Washington, D.C.
The finding applies especially to women, said Livingston, who performs the surgery. There are several types of bariatric surgery to treat severe obesity, the most common of which involves making the stomach smaller.
In his analysis, he found death from heart disease did not increase in a totally linear fashion the fatter people became. And he found distribution of body fat, rather than overall weight, is a better predictor of heart disease risk, with fat on the abdomen more unhealthy than that on the thighs and hips.
"One of the reasons we do these operations is there is a concern for early mortality attributed to obesity," Livingston explained. Traditional thinking has it that the heavier a person is, the more heart disease risk factors he or she has.
But Livingston had noticed among his patients that the degree of obesity did not always correlate with the amount of heart disease. So he looked at two large national databases -- the National Health Interview Surveys, from 1986 to 1994, as well as the National Death Index. He classified patients by body mass index (BMI) and looked at the prevalence of other heart disease risk factors such as blood pressure and cholesterol.
Death rates from heart disease increased for women when they passed a body mass index of 25 (about 160 pounds for a woman 5 feet 6 inches tall) and kept increasing until they reached a BMI of 30 (about 185 pounds for a woman of the same height) and then leveled off. People are considered obese when their BMI reaches 30, and are overweight when their BMI is between 25 and 30.
If obesity alone was considered, a woman of that height was found no more likely to die of heart disease at a BMI of 50 (about 310 pounds) than at a BMI of 35 (215 pounds).
For men, the death rate from heart disease continued to increase as BMI climbed, with a steep increase at a BMI of 40 (279 pounds for a man 5 feet 10 inches tall). As the BMI increased in men, at least up to 50, the highest they evaluated, so did heart disease death risk, Livingston said.
Fat distribution was key to heart disease death risk, he also found. There was a negative correlation with the buttock or thigh fat and a positive correlation with waist diameter.
It's the apple-pear story that's been told before: those who collect fat around their middles and are apple-shaped are less heart-healthy than the pears, who collect fat around the buttocks and thighs. Some who store fat in their lower bodies don't experience an increase in cholesterol, as do some who store it around their middle and become very obese with a rise in heart disease risk.
"What this means," said Livingston, "is that some people have the potential for becoming very obese by collecting fat in their lower body -- but that does not necessarily correlate to cardiovascular disease risk factors."
Currently, Livingston said, the criteria for bariatric surgery is based on size alone, with those at a BMI of 40 and above considered candidates.
"This [study] adds another piece to the puzzle about cardiovascular disease risk factors," he said.
The findings don't indicate that being obese is without risk, he said. But they do suggest that not everyone who is obese is always at increased risk of dying from heart disease.
But a cardiologist familiar with the study is skeptical. "It's an interesting observation, but there is not enough information to convince me," said Zi-Jian Xu, a cardiologist at Santa Monica/UCLA Medical Center in California.
"When obesity increases, your risk of heart disease increases," he said. "We have no reason to think risk will level off."