Effects of low-carbohydrate and low-fat diets: a randomized trial.

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.