Targeting dietary fat or glycemic load in the treatment of obesity and type 2 diabetes: a randomized controlled trial

Aims

To compare the effects of lifestyle modification programs that prescribe low-glycemic load (GL) vs. low-fat diets in a randomized trial.

Methods

Seventy-nine obese adults with type 2 diabetes received low-fat or low-GL dietary instruction, delivered in 40-week lifestyle modification programs with identical goals for calorie intake and physical activity. Changes in weight, HbA_1c, and other metabolic parameters were compared at weeks 20 and 40.

Results

Weight loss did not differ between groups at week 20 (low-fat: −5.7 ± 3.7%; low-GL: −6.7 ± 4.4%, p = .26) or week 40 (low-fat: −4.5 ± 7.5%; low-GL: −6.4 ± 8.2%, p = .28). Adjusting for changes in antidiabetic medications, subjects on the low-GL diet had larger reductions in HbA_1c than those on the low-fat diet at week 20 (low-fat: −0.3 ± 0.6%; low-GL: −0.7 ± 0.6%, p = .01), and week 40 (low-fat: −0.1 ± 1.2%; low-GL: −0.8 ± 1.3%; p = .01). Groups did not differ significantly on any other metabolic outcomes (p ≥ .06).

Conclusions

Results suggest that targeting GL, rather than dietary fat, in a low-calorie diet can significantly enhance the effect of weight loss on HbA_1c in patients with type 2 diabetes.