Underweight but metabolically abnormal phenotype: Metabolic features and its association with cardiovascular disease

•Nearly 20% of underweight people are identified as metabolically abnormal in China.•This underweight phenotype has comparable metabolic feature with obese people.•This underweight phenotype is associated with presence of cardiovascular disease.

BackgroundPrevious studies revealed that among people with normal and high body mass index (BMI), metabolic abnormalities contribute to the increased risk of cardiovascular disease (CVD). However, studies investigating the metabolic features and its association with CVD are limited.MethodsA national representative sample of adult population in China was used. Underweight was defined as BMI < 18.5 kg/m2. Participants who had less than 2 criteria of metabolic syndrome were classified as metabolically healthy; those who had 2 or more criteria of metabolic syndrome were classified as metabolically abnormal. Presence of CVD and albuminuria were compared among groups stratified by BMI and metabolic status.ResultsAmong 46 308 participants, 2267 (4.6%) were classified as underweight; and 372 (16.4%) of them were identified as metabolically abnormal. Metabolic features were comparable between underweight but metabolically abnormal participants and obese participants. Compared with participants with normal weight and normal metabolic features, the underweight but metabolically abnormal participants were more likely to have CVD and albuminuria, with an adjusted odds ratio of 2.33 (95% confidence interval (CI) 1.34–4.05) and 2.56 (95% CI 1.86–3.52), respectively. Among underweight participants, factors associated with metabolic abnormal phenotype included leisure time physical inactivity, mild occupational physical activity, and waist circumference.ConclusionsMetabolically abnormal phenotype is not rare among underweight population in China, and preventive strategy against CVD should also be considered in that population.