Obesity among metabolically healthy individuals does not appear to increase the risk of acute myocardial infarction (AMI). However, obesity, regardless of metabolic health, does increase the risk of heart failure (HF), according to new population-based data published in the Journal of the American College of Cardiology.

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The prospective cohort HUNT study looked at 61,299 men and women in Nord Trøndelag County in Norway. Waist circumference and body mass index (BMI) were measured and patients stratified into three groups: normal weight (<25 kg/m2), overweight (25-29.9 kg/m2) and obese (≥30 kg/m2). Metabolic health was determined using non-fasting glucose, triglyceride and HDL cholesterol levels, and blood pressure. Participants were considered metabolically unhealthy if they had an elevated waist circumference (men >94 cm, women >80 cm) or were obese plus had two or more of the following: elevated non-fasting triglycerides, reduced HDL cholesterol, hypertension or use of antihypertensive medications, elevated non-fasting glucose or diabetes.

During 12 years of follow-up, 2,547 participants suffered an AMI. In multivariate analysis, the hazard ratio for AMI was 1.1 (95 percent CI 0.9-1.4) among obese and metabolically healthy participants, and 2.0 among obese and metabolically unhealthy participants, as compared to normal weight, metabolically healthy individuals. For the 1,201 participants who developed HF, obesity, regardless of metabolic health, conferred a substantially increased risk. The hazard ratios for HF in the metabolically healthy and unhealthy obese were 1.7 (95 percent CI 1.2-2.3) and 1.7 (95 percent CI 1.4-2.2), respectively. Severe obesity and long-lasting obesity, regardless of metabolic health, appeared to further increase HF risk.

According to the study investigators, obesity combined with healthy metabolic status did not confer substantial excess risk for AMI, not even for long lasting or severe obesity. However, the risk of AMI among metabolically unhealthy individuals appeared to be increased across the whole range of BMI.

“In contrast to the risk of AMI, obesity may be more important than metabolic factors for the development of HF,” the study investigators said. “Accordingly, even metabolically healthy obesity is mostly associated with increased risk for HF, particularly for long lasting and severe obesity.”

In an accompanying editorial, Carl J. Lavie, MD, FACC, University of Queensland School of Medicine, New Orleans, and co-authors emphasized several factors from the study, noting that in the presence of substantial weight gain, “preventing and treating cardiometabolic abnormalities seems merited.” The editorial also points out that obesity increases HF risk regardless of metabolic status, and that, ultimately, measures to prevent overweightness and obesity should be emphasized and encouraged. “By improving levels of physical activity, and thus an individual’s level of fitness, one would prevent both CHD [coronary heart disease] and HF, and improve the prognosis in these disorders,” the authors note. “However, in our current society, achieving this goal may involve a considerable amount of wishful thinking.”

Keywords: Prognosis, Myocardial Infarction, Overweight, Heart Failure, Coronary Disease, Obesity, Diabetes Mellitus

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