Is obesity still a coronary risk factor?

Abstract

Although obesity and, in particular, abdominal obesity is clearly a risk factor for developing coronary artery disease, once coronary artery disease has been established, the correlation of obesity with total mortality, cardiovascular mortality, myocardial infarction, and revascularization is unclear and still remains a matter of debate. The relationship between obesity and mortality in patients with coronary artery disease has so far only been investigated by post-hoc analysis of cohort studies, which have produced contradictory results. When a higher percentage body fat has been found to be a strong independent predictor of event-free survival, the phenomenon has been described as an 'obesity paradox' or 'reverse epidemiology'. A recent meta-analysis, appearing in the August 19 issue of Lancet on 250.152 patients with documented coronary artery disease, suggests that after grouping 40 cohort studies with adjusted risks, overweight patients were consistently associated with a better survival and lower cardiovascular events than patients with a low body mass index, whereas obesity was associated with a higher total mortality only in patients with history of coronary artery bypass graft, and severe obesity was associated with a significantly higher cardiovascular mortality but not with an increased risk for total mortality. Far from proving that obesity is harmless, these findings suggest that alternative methods might be required to better characterize individuals who truly have excess body fat and that additional studies with different methods are needed. Moreover, still unknown is the unique contribution of higher muscle-to-fat ratio, which may be merely a surrogate of increased physical fitness. Future research is needed to assess the link between high muscle mass, high body fat and clinical outcomes.