LDL cholesterol rises with BMI only in lean individuals: Cross-sectional U.S. And Spanish representative data

Abstract

OBJECTIVE: Elevated LDL cholesterol (LDLc) is not strongly associated with obesity or metabolic syndrome (MS), but this relationship repeatedly has been examined assuming a linear association. This study aimed to assess the dose-response relationship between body mass index (BMI) or waist circumference (WC) and LDLc and to evaluate its link to metabolic impairment. RESEARCH DESIGN AND METHODS: Participants in the continuous National Health and Nutrition Examination Survey (NHANES, 1999-2010) (n = 12,383) and the Study on Nutrition and Cardiovascular Risk (ENRICA, 2008-2010) (n = 11,765), representative samples of U.S. and Spanish noninstitutionalized populations, were cross-sectionally investigated. LDLc was modeled with age- and sex-adjusted regressions, with BMI and/or WC as explanatory variables included in models as two-segment linear and natural cubic splines. RESULTS: In NHANES and ENRICA, slopes of the BMI-LDLc association changed (P < 0.001) at BMI 27.1 and 26.5 kg/m2, respectively, forming an inverted U shape. Below these BMI inflection points, LDLc rose 2.30 and 2.41 mg/dL per kg/m2 (both P < 0.001). However, above said points, LDLc declined 20.37 and 20.38 mg/dL per kg/m2 (both P < 0.001). The WC-LDLc relationship was similar to the BMI-LDLc relationship. Accumulation of MS traits was associated with a weakening of the positive BMI-LDLc association among lean participants (below the BMI inflection point). Aging shifted the inflection point of the BMI-LDLc relationship to lower BMI values. CONCLUSIONS: The BMI- and WC-LDLc relationships have inverted U shapes. Diminishing associations between BMI and LDLc might indicate metabolic impairment as a result of aging or other metabolic diseases. In lean individuals, small weight losses might help to lower LDLc for cardiovascular prevention.