Individuals who are metabolically healthy obese or underweight are at a higher risk of heart disease compared with metabolically healthy normal weight individuals, according to the largest study to date comparing weight and metabolic status with cardiovascular risk, published Sept. 11 in the Journal of the American College of Cardiology. Normal weight individuals with metabolic abnormalities showed similar risk as those who were healthy obese and healthy underweight.

Rishi Caleyachetty, MBBS, PhD, et al., compared electronic health records of 3.5 million British adults over a five-year follow-up period. The individuals were initially free from heart disease and divided into four body size phenotypes using body mass index: underweight (BMI less than 18.5), normal weight (more than 18 but less than 25), overweight (more than 25 but less than 30) and obese (more than 30). The study also factored in age, sex, smoking status and social deprivation (determined based on income, education and employment).

Approximately 15 percent of participants were classified as obese with no metabolic abnormalities. These individuals were most likely to be younger, male, current smokers and socially deprived. Those who were metabolically healthy obese had an increased risk of developing coronary heart disease, cerebrovascular disease and heart failure compared with individuals with normal weight and no metabolic abnormalities. Metabolically healthy obese individuals had a decreased risk of peripheral vascular disease compared with normal weight individuals with no metabolic abnormalities. Underweight individuals with zero metabolic abnormalities were also at an increased risk for cerebrovascular disease, heart failure and peripheral vascular disease. These risks may be due to smoking-related diseases such as chronic obstructive pulmonary disease and lung cancer. Underweight individuals who did not smoke were not found to have a risk for cerebrovascular disease.

According to the authors, the data show that at a population level, metabolically healthy obese is not a harmless condition and increases risk of cardiovascular events.

In an accompanying editorial comment, Jennifer Bea, PhD, writes, “With an impending obesity epidemic, examination of specific cardiovascular outcomes in this way is timely and highly significant. Caleyachetty et al. confirmed that obesity without metabolic abnormality is not benign. Even with no evident metabolic dysfunction, obese individuals were not ‘healthy.’” 

Keywords: Thinness, Body Mass Index, Smoking, Smoke, Cardiovascular Diseases, Follow-Up Studies, Risk Factors, Overweight, Body Weight Changes, Obesity, Body Size, Heart Failure, Pulmonary Disease, Chronic Obstructive, Heart Diseases, Coronary Disease, Cerebrovascular Disorders, Peripheral Vascular Diseases, Employment, Phenotype, Electronic Health Records, Lung Neoplasms

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