OBJECTIVE: Levels of fasting plasma glucose (FPG) and fasting insulin (FI) were studied as diet-specific prognostic markers for successful weight loss maintenance in participants with overweight.

METHODS: After losing ≥ 8% of body weight, participants received one of three ad libitum diets for 6 months: (1) a moderate-fat diet high in monounsaturated fatty acids (MUFA); (2) a low-fat, high-fiber diet (Nordic Nutrition Recommendations [NNR]); and (3) the Average Danish Diet (ADD). Participants were categorized as having low (< 90 mg/dL) or high (90-105 mg/dL) FPG based on preintervention values. Median FI among those having high FPG was used as a cutoff for FI (FI ≤ 50 pmol/L; FI > 50 pmol/L).

RESULTS: Participants with low FPG and randomized to MUFA, NNR, and ADD regained similarly 2.1 to 2.5 kg after 6 months. By contrast, participants with high FPG and randomized to MUFA, NNR, and ADD regained 2.73 kg (95% CI 1.33 to 4.13; P < 0.001), -0.05 kg (95% CI -1.95 to 1.86; P = 0.96), and 4.16 kg (95% CI 2.27 to 6.06; P < 0.001) after 6 months, respectively, resulting in lower weight regain on NNR compared to ADD (-4.21 kg [95% CI -6.83 to -1.59]; P = 0.002) and MUFA (95% CI -2.77 kg [-5.12 to -0.43]; P = 0.020). The addition of FI strengthened these associations.

CONCLUSIONS: Slightly elevated pretreatment FPG determined success in dietary weight loss maintenance among overweight patients on ad libitum diets differing in macronutrient and fiber content.