Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial

Ann Intern Med. 2014 Sep 2;161(5):309-18. doi: 10.7326/M14-0180.

Abstract

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.

Publication types

  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Aged
  • Blood Glucose / metabolism
  • Blood Pressure
  • C-Reactive Protein / metabolism
  • Cardiovascular Diseases / prevention & control*
  • Cholesterol, HDL / blood
  • Cholesterol, LDL / blood
  • Creatinine / blood
  • Diet, Carbohydrate-Restricted*
  • Diet, Fat-Restricted*
  • Female
  • Humans
  • Insulin / blood
  • Male
  • Middle Aged
  • Obesity / diet therapy*
  • Risk Factors
  • Triglycerides / blood
  • Waist Circumference
  • Weight Loss*
  • Young Adult

Substances

  • Blood Glucose
  • Cholesterol, HDL
  • Cholesterol, LDL
  • Insulin
  • Triglycerides
  • C-Reactive Protein
  • Creatinine

Associated data

  • ClinicalTrials.gov/NCT00609271