Much to their surprise, scientists at Duke University Medical Center have found that overweight and obese individuals actually have better survival rates for one year following a heart attack than normal-weight people.
Not so surprisingly, the researchers also determined the United States had the highest combined rate of obese and very obese people, while Asia had the highest percentage of normal-weight people.
The Duke team presented the findings April 1 at the American College of Cardiology's scientific sessions in Chicago.
One of the ironies in these findings, of course, is that being heavy is a risk factor for coronary artery disease, and may have been what helped land these patients in the hospital in the first place.
"We know that obesity is related to the development of coronary disease, so it's a risk factor. But for whatever reason, in this population, it doesn't seem to be associated with [poor] outcomes over the 90-day to one-year period," says Dr. Kristin Newby, co-author of the study and an associate professor of medicine at Duke University Medical Center. "The process of obesity as a risk factor for the development of coronary disease may be different than the way obesity affects short-term outcomes."
Newby and her colleagues had initially hypothesized that overweight and obese people would have higher mortality rates in the intermediate term.
To test the hypothesis, the researchers looked at data already collected for two related international trials and divided the 15,904 participants into four groups based on their body mass index (BMI): normal (BMI of 18.5 to 25), overweight (25 to 29.9), obese (30 to 34.9) and very obese (more than 35).
The results came as somewhat of a surprise to researchers used to equating overweight with poor health outcomes. One year after a heart attack, individuals in the obese grouping had the lowest death rate (2.2 percent), followed by those were classified as very obese (2.6 percent), overweight (2.7 percent mortality) and, finally, normal individuals bringing up the rear (4.3 percent).
Normal-weight participants also had the highest death rate after 90 days (2.6 percent) compared with overweight participants (1.6 percent), very obese participants (1.4 percent) and obese participants (1.3 percent).
A similar pattern was evident at 30 days, with normal weight individuals demonstrating a death rate of 1.7 percent, very obese individuals (1.2 percent), overweight individuals (1 percent), and obese individuals (0.9 percent).
The results may actually have more to do with the age of the people studied than their girth. "Youth hides a lot of sins," says Dr. Terrence Sacchi, chief of cardiology at Long Island University Hospital in New York City. "It seems that the patients in the overweight and obese group were younger, and also they were treated more aggressively."
"The findings still held up when adjusted in overweight and obese people, but not in the very obese group," says Eric Eisenstein, Newby's co-author and an assistant research professor in management at the Duke Clinical Research Institute. "Even after adjusting for all those factors, we still found that at one year the overweight and obese groups had a lower hazard of death than the normal people and the very obese people."
One thing to keep in mind is that this study looked only at intermediate-term survival, not long-term survival. "I don't think anyone is advocating remaining obese," Sacchi says. "It is associated with multiple risk factors."
Dr. Albert Chan, associate director of the catheterization laboratory at the Ochsner Clinic Foundation in New Orleans, says there may also be bias because the authors got their data from two different studies, which recruited people from different countries.
"What we don't want to come out of this is that we think weight control is a bad thing," Newby adds. "We don't understand these findings and we have a lot of work to do, but that doesn't mean that control of weight is not what we should be striving for. We only know out to about a year. There may be something that just happens in very short term, but over the long term there are still all the complications that come with obesity."
That means the United States is still in pretty bad shape when it comes to these risk factors. The study authors discovered this country had the highest rates of obese (24 percent) and very obese (13 percent) people and the lowest rates of normal (22 percent) people. Asia had the highest rate of normal-weight individuals (58 percent), Western Europe came next (31 percent), followed by Eastern Europe (29 percent), Latin America (28 percent), Australia/New Zealand (26 percent), and Canada (23 percent).
Australia/New Zealand and Canada tied for second place in the "very obese" category (7 percent each), followed by Latin America (6 percent), Eastern and Western Europe (4 percent each), and Asia (1 percent).