The notion that some people can be overweight or obese and still remain healthy is a myth, according to a new Canadian study.
Even without high blood pressure, diabetes or other metabolic issues, overweight and obese people have higher rates of death, heart attack and stroke after 10 years compared with their thinner counterparts, the researchers found.
"These data suggest that increased body weight is not a benign condition, even in the absence of metabolic abnormalities, and argue against the concept of healthy obesity or benign obesity," said researcher Dr. Ravi Retnakaran, an associate professor of medicine at the University of Toronto.
The terms healthy obesity and benign obesity have been used to describe people who are obese but don't have the abnormalities that typically accompany obesity, such as high blood pressure, high blood sugar and high cholesterol, Retnakaran explained.
"We found that metabolically healthy obese individuals are indeed at increased risk for death and cardiovascular events over the long term as compared with metabolically healthy normal-weight individuals," he added.
It's possible that obese people who appear metabolically healthy have low levels of some risk factors that worsen over time, the researchers suggest in the report, published online Dec. 3 in the Annals of Internal Medicine.
Dr. David Katz, director of the Yale University Prevention Research Center, welcomed the report. "Given the recent attention to the 'obesity paradox' in the professional literature and pop culture alike, this is a very timely and important paper," Katz said. (The obesity paradox holds that certain people benefit from chronic obesity.)
Some obese people appear healthy because not all weight gain is harmful, Katz said. "It depends partly on genes, partly on the source of calories, partly on activity levels, partly on hormone levels. Weight gain in the lower extremities among younger women tends to be metabolically harmless; weight gain as fat in the liver can be harmful at very low levels," Katz said.
A number of things, however, work to increase the risk of heart attack, stroke and death over time, he added.
"In particular, fat in the liver interferes with its function and insulin sensitivity," Katz said. This starts a domino effect, he explained. "Insensitivity to insulin causes the pancreas to compensate by raising insulin output. Higher insulin levels affect other hormones in a cascade that causes inflammation. Fight-or-flight hormones are affected, raising blood pressure. Liver dysfunction also impairs blood cholesterol levels," Katz said.
In general the things people do to make themselves fitter and healthier tend to make them less fat, he added.
"Lifestyle practices conducive to weight control over the long term are generally conducive to better overall health as well. I favor a focus on finding health over a focus on losing weight," Katz noted.
For the study, Retnakaran's team reviewed eight studies that looked at differences between obese or overweight people and slimmer people in terms of their health and risk for heart attack, stroke and death. These studies included more than 61,000 people overall.
In studies with follow-ups of a decade or more, those who were overweight or obese but didn't have high blood pressure, heart disease or diabetes still had a 24 percent increased risk for heart attack, stroke and death over 10 years or more, compared with normal-weight people, the researchers found.
Greater risk for heart attack, stroke and death was seen among all those with metabolic disease (such as high cholesterol and high blood sugar) regardless of weight, the researchers noted.
As a result, doctors should consider both body mass and metabolic tests when evaluating someone's health risks, the researchers concluded.
