Study Title
Effects of Low-Carbohydrate and Low-Fat Diets
Annals of Internal Medicine

Lydia A. Bazzano, MD, PhD, MPH; Tian Hu, MD, MS; Kristi Reynolds, PhD; Lu Yao, MD, MS; Calynn Bunol, MS, RD, LDN; Yanxi Liu, MS; Chung-Shiuan Chen, MS; Michael J. Klag, MD, MPH; Paul K. Whelton, MD, MSc, MB; and Jiang He, MD, PhD


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.
Setting: A large academic medical center.
Participants: 148 men and women without clinical cardiovascular disease and diabetes.
Intervention: A low-carbohydrate (less than 40 g/d) or low-fat (less than 40 g/d) or low-fat (less than 30% of daily energy intake from total fat [less than 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, -3.5kg [95% CI, -5.6 to -1.4kg]; P= 0.002), fat mass (mean difference in change, -1.5% [Cl, -2.6% to -0.4%]; P= 0.011, ratio of total-high density lipoprotein (HDL) cholesterol (mean difference in change, -0.44 [Cl, -0.71 to -0.16] mmol/L [-14.1 mg/dL] [Cl, -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/gL] [Cl, 0.08 to 0.28 mmol/dL {3.0 to 11.0 mg/dL}]; P less than 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.

September 2, 2014
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Weight LossLow-CarbLow-FatCardiovascular Risk Factors

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