"Metabolically healthy" overweight and obese patients may carry the same short-term risk as normal-weight patients for all-cause mortality and cardiovascular events, but their weight puts them at increased risk over the long term, according to a report published online Dec. 2 in Annals of Internal Medicine.
Several studies have reported finding a subgroup of obese individuals who have normal metabolic features despite their high adiposity, and the researchers have called this condition "benign obesity" or "metabolically healthy obesity." Such patients reportedly have the same or even lower all-cause mortality and CV risk as normal-weight patients. But those studies tended to have short follow-up, making their conclusions somewhat questionable, said Dr. Caroline K. Kramer of the Leadership Sinai Centre for Diabetes, Toronto, and her associates.
The findings from their meta-analysis of eight observational studies indicate that excess weight confers increased risk after 10 years, even in "metabolically healthy" obese patients. "Our results do not support this concept of ‘benign obesity’ and demonstrate that there is no ‘healthy’ pattern of obesity," the researchers wrote (Ann. Intern. Med. 2013 Dec. 2;159 [doi=10.7326/0003-4819-159-11-201312030-00002]).
Dr. Kramer and her colleagues pooled the results of eight studies that examined participants’ metabolic status as well as weight, which had follow-up intervals ranging from 3 years to 30 years. That yielded a sample of 61,386 patients, with 3,988 deaths or CV events.
Metabolic status was categorized as either healthy or unhealthy, depending on factors such as lipid profile, glucose tolerance, blood pressure, insulin resistance, and waist circumference.
In an initial analysis, overweight and obese patients who were metabolically healthy had similar outcomes as metabolically healthy normal-weight patients. But when the analysis was confined to studies with at least 10 years of follow-up, the metabolically healthy obese group had increased mortality and CV risk, with a risk ratio of 1.24.
In addition, all patients who were metabolically unhealthy were at increased risk for death and CV events, regardless of their weight. In fact, normal-weight patients who were metabolically unhealthy carried the same risk of death or CV events as did overweight and obese patients who were metabolically unhealthy. That indicates that normal-weight patients who are metabolically unhealthy are a patient population that merits particular attention in clinical practice, the investigators said.
"Our findings highlight the need for comprehensive evaluation of not only BMI [body mass index] but also metabolic factors for the prediction of future morbidity and mortality," Dr. Kramer and her associates said.
The findings also show that duration of follow-up "is a critical element in evaluating low-risk populations for future events, the researchers noted.
The investigators proposed that in patients erroneously deemed to have "benign obesity" or "metabolically healthy obesity," excess weight is associated with subclinical metabolic and vascular dysfunction that ultimately leads to increased mortality and CV events over time.
Dr. Kramer had no relevant conflicts of interest. One of her coauthors reported receiving grants and fees from Merck and Novo Nordisk.