Abstract P142: Mediation of Effects of a Low-Carbohydrate Dietary Intervention on Hemoglobin A1c Through Weight: A Randomized Clinical Trial

Introduction: Low-carbohydrate diets lead to weight loss and improvement in hemoglobin A1c and other cardiometabolic outcomes. However, there is limited research on how much of the glycemic effects of low-carbohydrate diets are mediated by weight loss. Hypothesis: The effect of a low-carbohydrate dietary intervention on hemoglobin A1c would be mediated by weight loss. Methods: We conducted a 6-month randomized clinical trial on the effects of a low-carbohydrate diet intervention (target Results: 150 participants (mean [SD] age 59 [8] years; 108 [72%] female; 88 [59%] Black) were randomized to either the low-carbohydrate diet intervention (75 participants) or usual diet (75 participants) arm. Mean (SD) HbA1c was 6.16% (0.30%) at baseline. Six-month data was collected on 142 participants (95%). Compared with the usual diet arm, the low-carbohydrate diet intervention arm had significantly greater 6-month reduction in HbA1c (net difference, -0.23% [95% CI, -0.32 to -0.14%]) and body weight (-5.9 kg [95% CI, -7.4 to -4.4 kg]). In mediation analyses, 59% of the total effect of intervention on 6-month change in hemoglobin A1c was mediated by weight measured at 3 months (Table). Conclusions: In mediation analyses, a substantial proportion (59%) of the total effect of intervention on 6-month change in hemoglobin A1c was mediated through weight measured at 3 months. Future research should further explore contributions of weight loss to reductions in glycemia in other populations.