Healthy obesity a myth, say researchers at Mount Sinai Hospital

Obesity carries an additional risk of premature death compared to that of normal-weight individuals, regardless of the obese person’s cholesterol and sugar levels, a study from Mount Sinai Hospital’s Lunenfeld-Tanenbaum Research Institute shows.

“Our research findings challenge the myth that there is such a thing as healthy obesity if people maintain normal-range readings of cholesterol, blood glucose, and blood pressure,” says co- author Dr. Ravi Retnakaran, an endocrinologist at the Leadership Sinai Diabetes Centre at Mount Sinai Hospital in Toronto, and Associate Member of the hospital’s Lunenfeld-Tanenbaum Research Institute. Co-authors are Dr. Caroline K. Kramer and Dr. Bernard Zinman, also of the Lunenfeld-Tanenbaum Research Institute.

The paper was published on-line in Annals of Internal Medicine, December 2. The journal supported the paper with an independent editorial commentary stressing the findings’ importance for both clinical and policy considerations.

Lead author Dr. Caroline Kramer with Dr. Bernard Zinman, Senior Investigator

at the Lunenfeld-Tanenbaum Research Institute.

Researchers reviewed the data of 61,386 individuals in eight separate studies from the past decade.  Each study observed adults defined as normal weight, overweight, and obese (body mass index or BMI of 30 or greater). Each study evaluated the individuals’ metabolic status, i.e. cholesterol levels, blood sugar levels, and blood pressure. The studies compared fatal and nonfatal cardiovascular events such as heart attack and stroke, as well as other causes of death, across the three weight categories. 

The comparative risks for premature death in the three weight groups became especially apparent after 10 years of follow-up.

The key finding is that even in the absence high blood pressure or cholesterol (in other words, a metabolic problem), an obese person whose BMI is 30 or greater may be at 24% additional risk for cardiovascular event or premature death compared to a person of normal weight, says Dr. Retnakaran.

“The finding of increased risk of death or cardiovascular events for obese individuals suggests that gaining excess weight is associated with risk that may accumulate over time, even before metabolic and cardiovascular signs become apparent in lab tests,” adds Dr. Retnakaran. “This is a signal to general practitioners and family physicians to guide their obese patients to weight loss, regardless of lab tests,” he says.

Co-author Dr. Ravi Retnakaran

The compiled data of more than 60,000 people make this finding a sturdy and significant guidepost for treating physicians, says Dr. Bernard Zinman. “When we compared the three weight groups, we found that obesity stood out as the key risk factor for premature death from any cause, including cardiovascular events. That’s true for obese people with so-called healthy metabolic status as well as obese people with poor metabolic status – that is, high blood pressure, cholesterol, and blood glucose levels,” he says. Dr. Zinman is a Senior Investigator at the Lunenfeld-Tanenbaum Research Institute and Director of the Leadership Sinai Centre for Diabetes at Mount Sinai Hospital.

Additional findings in this study include:

• Increased risk is presented by poor metabolic status, regardless of weight – i.e., both overweight and obese individuals are at the same level of risk
• “Blood pressure, waist circumference, and insulin resistance increased, and HDL cholesterol decreased, across the BMI categories” in people with both healthy and unhealthy metabolic status

The findings are also important from a policy perspective, explains lead author Dr. Caroline Kramer. “The idea that we don’t need to target health care resources toward obese people whose lab tests are ‘normal’ turns out to be false,” she says. Dr. Kramer is a post-doctoral fellow at the Lunenfeld-Tanenbaum Research Institute.

“Our message to physicians is that for obese individuals, normal metabolic status regarding blood pressure, cholesterol and blood glucose is not protective. If they can start to lose weight, that’s a benefit,” she says.

This perspective is supported by the Annals’ editorial, which says that the study “fuels the debate about the existence of a subset of obese persons who […] should not be targeted for treatment.” 

The researchers are funded by Leadership Sinai Centre for Diabetes, Canadian Diabetes Association, Sam and Judy Pencer Family Chair in Diabetes Research, and Ontario Ministry of Research and Innovation. The paper is called: Are Metabolically Healthy Overweight and Obesity Benign Conditions? A  Systematic Review and Meta-analysis of the Effect of Body Mass Index and Metabolic Status Phenotypes on All-cause Mortality and Cardiovascular Events.