The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial
Background: A previous paper reported the 6-month comparison of weight loss and metabolic changes in obese adults randomly assigned to either a low-carbohydrate diet or a conventional weight loss diet.
Objective: To review the 1-year outcomes between these diets.
Design: Randomized trial.
Setting: Philadelphia Veterans Affairs Medical Center.
Participants: 132 obese adults with a body mass index of 35 kg/m2 or greater; 83% had diabetes or the metabolic syndrome.
Intervention: Participants received counseling to either restrict carbohydrate intake to <30 g per day (low-carbohydrate diet) or to restrict caloric intake by 500 calories per day with <30% of calories from fat (conventional diet).
Measurements: Changes in weight, lipid levels, glycemic control, and insulin sensitivity.
Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was –5.1 ± 8.7 kg compared with –3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (–1.9 kg [95% CI, –4.9 to 1.0 kg]; P = 0.20). For persons on the low-carbohydrate diet, triglyceride levels decreased more (P = 0.044) and high-density lipoprotein cholesterol levels decreased less (P = 0.025). As seen in the small group of persons with diabetes (n = 54) and after adjustment for covariates, hemoglobin A1c levels improved more for persons on the low-carbohydrate diet. These more favorable metabolic responses to a low-carbohydrate diet remained significant after adjustment for weight loss differences. Changes in other lipids or insulin sensitivity did not differ between groups.
Limitations: These findings are limited by a high dropout rate (34%) and by suboptimal dietary adherence of the enrolled persons.
Conclusion: Participants on a low-carbohydrate diet had more favorable overall outcomes at 1 year than did those on a conventional diet. Weight loss was similar between groups, but effects on atherogenic dyslipidemia and glycemic control were still more favorable with a low-carbohydrate diet after adjustment for differences in weight loss.