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A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia
A Randomized, Controlled Trial
- William S. Yancy, Jr., MD, MHS;
- Maren K. Olsen, PhD;
- John R. Guyton, MD;
- Ronna P. Bakst, RD; and
- Eric C. Westman, MD, MHS
- From the Center for Health Services Research in Primary Care, Department of Veterans Affairs Medical Center, and Duke University Medical Center, Durham, North Carolina.
Abstract
Background: Low-carbohydrate diets remain popular despite a paucity of scientific evidence on their effectiveness.
Objective: To compare the effects of a low-carbohydrate, ketogenic diet program with those of a low-fat, low-cholesterol, reduced-calorie diet.
Design: Randomized, controlled trial.
Setting: Outpatient research clinic.
Participants: 120 overweight, hyperlipidemic volunteers from the community.
Intervention: Low-carbohydrate diet (initially, <20 g of carbohydrate daily) plus nutritional supplementation, exercise recommendation, and group meetings, or low-fat diet (<30% energy from fat, <300 mg of cholesterol daily, and deficit of 500 to 1000 kcal/d) plus exercise recommendation and group meetings.
Measurements: Body weight, body composition, fasting serum lipid levels, and tolerability.
Results: A greater proportion of the low-carbohydrate diet group than the low-fat diet group completed the study (76% vs. 57%; P = 0.02). At 24 weeks, weight loss was greater in the low-carbohydrate diet group than in the low-fat diet group (mean change, −12.9% vs. −6.7%; P < 0.001). Patients in both groups lost substantially more fat mass (change, −9.4 kg with the low-carbohydrate diet vs. −4.8 kg with the low-fat diet) than fat-free mass (change, −3.3 kg vs. −2.4 kg, respectively). Compared with recipients of the low-fat diet, recipients of the low-carbohydrate diet had greater decreases in serum triglyceride levels (change, −0.84 mmol/L vs. −0.31 mmol/L [−74.2 mg/dL vs. −27.9 mg/dL]; P = 0.004) and greater increases in high-density lipoprotein cholesterol levels (0.14 mmol/L vs. −0.04 mmol/L [5.5 mg/dL vs. −1.6 mg/dL]; P < 0.001). Changes in low-density lipoprotein cholesterol level did not differ statistically (0.04 mmol/L [1.6 mg/dL] with the low-carbohydrate diet and −0.19 mmol/L [−7.4 mg/dL] with the low-fat diet; P = 0.2). Minor adverse effects were more frequent in the low-carbohydrate diet group.
Limitations: We could not definitively distinguish effects of the low-carbohydrate diet and those of the nutritional supplements provided only to that group. In addition, participants were healthy and were followed for only 24 weeks. These factors limit the generalizability of the study results.
Conclusions: Compared with a low-fat diet, a low-carbohydrate diet program had better participant retention and greater weight loss. During active weight loss, serum triglyceride levels decreased more and high-density lipoprotein cholesterol level increased more with the low-carbohydrate diet than with the low-fat diet.
Article and Author Information
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Acknowledgments: The authors thank Keith Tomlin, Bill Bryson, Juanita Hepburn, Christine Perkins, and Angela Braswell for assistance with the interventions and data collection; David Simel and John Williams for manuscript review; and John J.B. Anderson, Howard Eisenson, Jarol Boan, Jim Lane, Truls Ostbye, and Robert Rosati, members of the Oversight Committee.
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Grant Support: By the Robert C. Atkins Foundation, New York, New York. Dr. Yancy is supported by a Veterans Administration Health Services Research Career Development Award.
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Potential Financial Conflicts of Interests:Grants received: E.C. Westman (Robert C. Atkins Foundation); Grants pending: E.C. Westman and W.S. Yancy Jr. (Robert C. Atkins Foundation).
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Requests for Single Reprints: Eric C. Westman, MD, MHS, Duke University Medical Center, Box 50, Suite 200-B Wing, 2200 West Main Street, Durham, NC 27705; e-mail, ewestman{at}duke.edu.
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Current Author Addresses: Drs. Yancy and Olsen: Health Services Research and Development (152), Veterans Affairs Medical Center, 508 Fulton Street, Durham, NC 27705.
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Dr. Guyton: Duke Lipid Clinic, Duke University Medical Center, Box 3510, Durham, NC 27710.
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Ms. Bakst: Duke University Medical Center, Box 3921, Durham, NC 27710.
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Dr. Westman: Duke University Medical Center, Box 50, Suite 200-B Wing, 2200 West Main Street, Durham, NC 27705.
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Author Contributions: Conception and design: W.S. Yancy Jr., E.C. Westman.
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Analysis and interpretation of the data: W.S. Yancy Jr., M.K. Olsen, J.R. Guyton, E.C. Westman.
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Drafting of the article: W.S. Yancy Jr., J.R. Guyton, E.C. Westman.
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Critical revision of the article for important intellectual content: W.S. Yancy Jr., M.K. Olsen. J.R. Guyton, R.P. Bakst, E.C. Westman.
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Final approval of the article: W.S. Yancy Jr., M.K. Olsen, J.R. Guyton, R.P. Bakst, E.C. Westman.
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Provision of study materials or patients: W.S. Yancy Jr., E.C. Westman.
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Statistical expertise: W.S. Yancy Jr., M.K. Olsen, E.C. Westman.
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Obtaining of funding: E.C. Westman.
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Administrative, technical, or logistic support: R.P. Bakst, E.C. Westman.
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Collection and assembly of data: W.S. Yancy Jr., R.P. Bakst, E.C. Westman.
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