Restricted Carbohydrate Diets High in Fat Are Associated with Increased Likelihood of Prevalent Metabolic Syndrome

OBJECTIVES: This study evaluated the association between a restricted carbohydrate diet (<45% energy from carbohydrate) and metabolic syndrome stratified by fatty acid classes in a nationally representative sample of U.S adults. METHODS: Data on food and nutrient intake, and markers of metabolic syndrome, were obtained from 19,078 respondents ≥20 y in the National Health and Nutrition Examination Survey (NHANES) 1999–2018. The National Cancer Institute's usual intake methodology was used to evaluate the associations between usual dietary intake and prevalent metabolic syndrome. RESULTS: Compared to individuals that met all AMDR macronutrient recommendations, the odds of having metabolic syndrome were 1.085 (95%CI: 1.077–1.094) times higher among those that consumed a restricted carbohydrate diet (P < 0.001) and 1.115 (1.153–1.156) times higher for those that met only current recommendations for total carbohydrates (P < 0.001). Higher fat intake, regardless of class, was associated with increased likelihood of metabolic syndrome among individuals that consumed restricted carbohydrate diets but not among individuals that met current carbohydrate recommendations. CONCLUSIONS: The likelihood of prevalent metabolic syndrome was moderately higher (8.5%) among individuals that consumed restricted carbohydrate diets compared to individuals that met all macronutrient recommendations. High intake of fat of any class was associated with increased likelihood of metabolic syndrome in those consuming a restricted carbohydrate diet. FUNDING SOURCES: This work was supported by the Institute for the Advancement of Food and Nutrition Sciences (IAFNS) Carbohydrate and Lipid Committees. IAFNS is a nonprofit science organization that pools funding from industry collaborators and advances science through the in-kind and financial contributions from public and private sector participants. IAFNS had no role in the design, analysis, interpretation, or presentation of the data and results.