Obesity has been associated with metabolic disorders such as type 2 diabetes, high cholesterol levels, high triglycerides levels, increased visceral fat deposits, and high blood pressure. Obesity has also been associated with the metabolic syndrome, a condition which increases cardiovascular risk and predisposes to heart attack and stroke. As a result, obesity has generally been considered an unhealthy state. There are some obese individuals who do not have any of the previously mentioned metabolic disorders. Despite being obese, these individuals are generally metabolically healthy and lead an active lifestyle, obtain regular exercise, and are physically fit. It has been unclear whether these metabolically healthy but obese individuals have the same heart health risks as those individuals that are metabolically unhealthy and obese.
Researchers, led by Dr. Francisco Ortega of the University of Granada in Spain, have found that individuals that are metabolically healthy but obese do not have increased risk of heart disease. The results of their study were published online in the European Heart Journal. The researchers measured physical fitness by exercise testing and body fat was measured by body mass index (BMI) and body fat percent by hydrostatic weighing or skinfolds in 43,265 study participants. Metabolically healthy was defined as meeting 0 or 1 of the criteria for metabolic syndrome. Metabolically healthy but obese individuals had 38% lower risk of all-cause mortality, and 30-50% lower risk of non-fatal and fatal cardiovascular disease, and cancer mortality when compared to metabolically unhealthy and obese individuals. In addition, there was no observed difference between metabolically healthy but obese and metabolically healthy normal fat individuals.
The authors wrote, “The results of the present study suggest that: (i) metabolically healthy but obese individuals have better fitness than their metabolically abnormal obese peers, both in men and women and using BMI or [body fat percent] to define obesity; (ii) for a given fitness level, the metabolically healthy but obese phenotype is a benign condition, since these individuals had a lower risk for mortality and morbidity than that observed in metabolically abnormal obese individuals”.
The authors also wrote, “The results from the current study have important clinical implications. Our data suggest that accurate [body fat percent] and fitness assessment can contribute to properly define a subset of obese individuals who do not have an elevated risk of [cardiovascular disease] or cancer”.
In an accompanying editorial it was commented, “Obesity may carry benefit up to a certain degree, and it should be recognized that obesity is not necessarily associated with abnormal metabolic function”.
This study suggests that obesity is important for health based upon where the fat is carried and how obesity affects other aspects of health. Obesity in and of itself does not appear to be a health risk factor if the individual has good physical fitness. When obesity is associated with type 2 diabetes, high blood pressure, high triglycerides, and the metabolic syndrome, it should be considered an unhealthy state. Despite this though, as this study has pointed out, metabolically healthy but obese appears to be a benign condition that does not carry increased morbidity and mortality risk.
Francisco B. Ortega et al. “The intriguing metabolically healthy but obese phenotype: cardiovascular prognosis and role of fitness” European Heart Journal First published online September 4, 2012 doi: 10.1093/eurheartj/ehs174