Some obese people have no greater risk of cardiovascular disease or cancer than normal-weight people, a new study suggests.
Moreover, for patients with heart disease, being obese may actually reduce the risk of death, a phenomenon called the "obesity paradox," another study finds.
"It is possible to be fat and fit -- but relatively few people are," said Dr. David Katz, director of the Prevention Research Center at Yale University School of Medicine. He took no part in either study.
"For the most part, the behaviors that promote fitness most effectively defend against fatness into the bargain. It is certainly possible to be thin and unhealthy, which is why health, not a particular weight, is what we should be aiming for as both individuals and a society," he said.
Both reports were published online Sept. 5 in the European Heart Journal.
For the first study, a team led by Francisco Ortega, of the department of biosciences and nutrition at the Karolinska Institute in Stockholm, collected data on more than 43,000 people who were part of the Aerobics Center Longitudinal Study.
Study participants were mostly white (98 percent), and were well-educated and worked in executive or professional positions.
Each participant answered questions about medical history and lifestyle, and took a treadmill test to evaluate their cardiovascular fitness. In addition, their height, weight, percent of body fat and waist size were measured, as well as blood pressure, cholesterol and blood sugar.
Study participants were recruited between 1979 and 2003, and followed until the end of 2003 or until they died.
The researchers found that among obese individuals, 46 percent were heart healthy and had a 38 percent lower risk of dying than those obese people who were not heart healthy.
Moreover, those healthy obese had the same reduced risk of heart disease and cancer as healthy normal-weight people, they added. Both groups had a 30 percent to 50 percent reduction in their risk for cardiovascular disease or cancer compared to obese people who were not heart healthy, the researchers found.
"Not every obese person is equally healthy/unhealthy," Ortega said. "There is a relatively large subset of obese people that are metabolically healthy, and if obesity is defined using body-fat percent (instead of body-mass index) and cardiac-respiratory fitness is taken into account, the future prognosis of metabolically healthy but obese people is similar to that of normal-weight people," he said.
Doctors should take into consideration that not all obese people have the same prognosis, Ortega said.
"Physicians could assess fitness, fatness and metabolic markers to do a better estimation of the risk of cardiovascular disease and cancer of obese patients," Ortega explained. "Our data support the idea that interventions might be more urgently needed in metabolically unhealthy and unfit obese people, since they are at a higher risk," he said.
Dr. Gregg Fonarow, a spokesman for the American Heart Association and professor of cardiology at the University of California, Los Angeles, said the study follow-up period was too short to really determine if obese people in the study were heart healthy.
"This study followed individuals for 15 years -- further studies are needed to determine the long-term health consequences of obesity in these individuals," he said.
In the second study, Dr. Oskar Angeras, a consultant cardiologist at the Sahlgrenska Academy of the University of Gothenburg in Sweden, and colleagues collected data on more than 64,000 people in the Swedish Coronary Angiography and Angioplasty Registry, who had heart disease or had a heart attack between May 2005 and December 2008.