Effects of Low-Carbohydrate and Low-Fat Diets

BACKGROUND: Low-carbohydrate diets are popular for weight loss, but their cardiovascular effects have not been well-studied, particularly in diverse populations. OBJECTIVE: To examine the effects of a low-carbohydrate diet compared with a low-fat diet on body weight and cardiovascular risk factors. DESIGN: A randomized, parallel-group trial. (ClinicalTrials. gov: NCT00609271). SETTING: A large academic medical center. PARTICIPANTS: 148 men and women without clinical cardiovascular disease and diabetes. INTERVENTION: A low-carbohydrate (<40 g/d) or low-fat (<30% of daily energy intake from total fat <7% saturated fat) diet. Both groups received dietary counseling at regular intervals throughout the trial. MEASUREMENTS: Data on weight, cardiovascular risk factors, and dietary composition were collected at 0, 3, 6, and 12 months. RESULTS: Sixty participants (82%) in the low-fat group and 59 (79%) in the low-carbohydrate group completed the intervention. At 12 months, participants on the low-carbohydrate diet had greater decreases in weight (mean difference in change, -3. 5 kg 95% CI, -5. 6 to -1. 4 kg; P = 0. 002), fat mass (mean difference in change, -1. 5% CI, -2. 6% to -0. 4%; P = 0. 011), ratio of total-high-density lipoprotein (HDL) cholesterol (mean difference in change, -0. 44 CI, -0. 71 to -0. 16; P = 0. 002), and triglyceride level (mean difference in change, -0. 16 mmol/L -14. 1 mg/dL CI, -0. 31 to -0. 01 mmol/L -27. 4 to -0. 8 mg/dL; P = 0. 038) and greater increases in HDL cholesterol level (mean difference in change, 0. 18 mmol/L 7. 0 mg/dL CI, 0. 08 to 0. 28 mmol/L 3. 0 to 11. 0 mg/dL; P < 0. 001) than those on the low-fat diet. LIMITATION: Lack of clinical cardiovascular disease end points. CONCLUSION: The low-carbohydrate diet was more effective for weight loss and cardiovascular risk factor reduction than the low-fat diet. Restricting carbohydrate may be an option for persons seeking to lose weight and reduce cardiovascular risk factors. PRIMARY FUNDING SOURCE: National Institutes of Health.