The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-up of a Randomized Trial

  1. Linda Stern, MD;
  2. Nayyar Iqbal, MD;
  3. Prakash Seshadri, MD;
  4. Kathryn L. Chicano, CRNP;
  5. Denise A. Daily, RD;
  6. Joyce McGrory, CRNP;
  7. Monica Williams, BS;
  8. Edward J. Gracely, PhD; and
  9. Frederick F. Samaha, MD
  1. From Philadelphia Veterans Affairs Medical Center, University of Pennsylvania Medical Center, and Drexel University College of Medicine, Philadelphia, Pennsylvania.

    Abstract

    Background: A previous paper reported the 6-month comparison of weight loss and metabolic changes in obese adults randomly assigned to either a low-carbohydrate diet or a conventional weight loss diet.

    Objective: To review the 1-year outcomes between these diets.

    Design: Randomized trial.

    Setting: Philadelphia Veterans Affairs Medical Center.

    Participants: 132 obese adults with a body mass index of 35 kg/m2 or greater; 83% had diabetes or the metabolic syndrome.

    Intervention: Participants received counseling to either restrict carbohydrate intake to <30 g per day (low-carbohydrate diet) or to restrict caloric intake by 500 calories per day with <30% of calories from fat (conventional diet).

    Measurements: Changes in weight, lipid levels, glycemic control, and insulin sensitivity.

    Results: By 1 year, mean (±SD) weight change for persons on the low-carbohydrate diet was −5.1 ± 8.7 kg compared with −3.1 ± 8.4 kg for persons on the conventional diet. Differences between groups were not significant (−1.9 kg [95% CI, −4.9 to 1.0 kg]; P = 0.20). For persons on the low-carbohydrate diet, triglyceride levels decreased more (P = 0.044) and high-density lipoprotein cholesterol levels decreased less (P = 0.025). As seen in the small group of persons with diabetes (n = 54) and after adjustment for covariates, hemoglobin A1c levels improved more for persons on the low-carbohydrate diet. These more favorable metabolic responses to a low-carbohydrate diet remained significant after adjustment for weight loss differences. Changes in other lipids or insulin sensitivity did not differ between groups.

    Limitations: These findings are limited by a high dropout rate (34%) and by suboptimal dietary adherence of the enrolled persons.

    Conclusion: Participants on a low-carbohydrate diet had more favorable overall outcomes at 1 year than did those on a conventional diet. Weight loss was similar between groups, but effects on atherogenic dyslipidemia and glycemic control were still more favorable with a low-carbohydrate diet after adjustment for differences in weight loss.

    Article and Author Information

    • Acknowledgment: The authors thank Dr. Stephen E. Kimmel and Dr. David Asch for their detailed review and comments on this manuscript, as well as Dr. Justine Shults for her valuable consultation on the statistical analyses.

    • Grant Support: By the Veterans Affairs Healthcare Network Competitive Pilot Project Grant.

    • Potential Financial Conflicts of Interest: None disclosed.

    • Requests for Single Reprints: Frederick F. Samaha, MD, Cardiology, 8th Floor, MC 111C, Philadelphia Veterans Affairs Medical Center, University and Woodland Avenue, Philadelphia, PA 19104; e-mail, rick.samaha{at}med.va.gov.

    • Current Author Addresses: Drs. Stern, Iqbal, Seshadri, and Samaha, Ms. Chicano, Ms. Daily, Ms. McGrory, and Ms. Williams: Philadelphia Veterans Affairs Medical Center, Cardiology, 8th Floor MC 111C, University and Woodland Avenues, Philadelphia, PA 19104.

    • Dr. Gracely: Family, Community, and Preventive Medicine, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129.

    • Author Contributions: Conception and design: L. Stern, N. Iqbal, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, E.J. Gracely, F.F. Samaha.

    • Analysis and interpretation of the data: P. Seshadri, E.J. Gracely, F.F. Samaha.

    • Drafting of the article: L. Stern, N. Iqbal, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, F.F. Samaha.

    • Critical revision of the article for important intellectual content: L. Stern, N. Iqbal, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, E.J. Gracely, F.F. Samaha.

    • Final approval of the article: L. Stern, N. Iqbal, P. Seshadri, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, E.J. Gracely, F.F. Samaha.

    • Provision of study materials or patients: L. Stern, N. Iqbal, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, F.F. Samaha.

    • Statistical expertise: E.J. Gracely, F.F. Samaha.

    • Obtaining of funding: L. Stern, N. Iqbal, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, F.F. Samaha.

    • Administrative, technical, or logistic support: F.F. Samaha.

    • Collection and assembly of data: L. Stern, N. Iqbal, P. Seshadri, K.L. Chicano, D.A. Daily, J. McGrory, M. Williams, F.F. Samaha.

    Responses to this article

    • Low Carbohydrate Diet
      • Dean Ornish
      Ann Intern Med published online October 26, 2009
    • Low Carbohydrate Diets and Cardiovascular Risk
      • Frederick F. Samaha and
      • Frederick F. Samaha and Linda Stern
      Ann Intern Med published online October 26, 2009

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    1. Ann Intern Med May 18, 2004 vol. 140 no. 10 778-785
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