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Comparison of Popular Weight Loss Diets

This study has been completed.
Community Foundation of Southeastern Michigan
Information provided by:
National Center for Complementary and Integrative Health (NCCIH) Identifier:
First received: March 9, 2004
Last updated: August 16, 2006
Last verified: August 2006
This study will compare the safety and effectiveness of three popular weight loss plans. These plans will be compared with the USDA Dietary Guidelines.

Condition Intervention Phase
Obesity Behavioral: Atkins diet (extremely low carbohydrate) Behavioral: Zone diet (low carbohydrate, high protein) Behavioral: Ornish diet (very low fat) Phase 2

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single
Primary Purpose: Treatment
Official Title: Benefits & Risks of Popular Weight Loss Diets

Resource links provided by NLM:

Further study details as provided by National Center for Complementary and Integrative Health (NCCIH):

Primary Outcome Measures:
  • Weight; measured at each study visit
  • Percent body fat; measured at each study visit

Secondary Outcome Measures:
  • Blood lipids (cholesterol, triglycerides); measured at each study visit
  • Fasting insulin and glucose; measured at each study visit
  • Behavioral variables; measured at each study visit

Estimated Enrollment: 300
Study Start Date: July 2002
Estimated Study Completion Date: June 2004
Detailed Description:

Obesity is the single most significant, nutrition-related health issue of the new millennium. Several “medical experts” have designed and promoted weight loss diets that dramatically differ from one another and from the USDA Dietary Guidelines. These diets have gained surprisingly widespread and persistent popularity among Americans despite the lack of evidence supporting their claims. This clinical trial will provide preliminary feasibility data for a full-scale study that will examine health outcomes (e.g., benefits, risks, success) of three popular weight loss diets. The study will investigate behavioral and physiological factors that influence adherence and retention to these diet plans.

Overweight women will be randomly assigned to one of four diets for 1 year: Atkins (extremely low carbohydrate), Zone (low carbohydrate, high protein), Ornish (very low fat), or USDA/Food Pyramid (high carbohydrate/moderate-low fat). Behavioral and physiological data will be collected. Participants attend study visits at baseline, 8 weeks, 6 months, and 1 year. At these visits, measurements will include that will include weight and blood pressure measurements and blood tests. Participants will be asked to complete ten questionnaires over the course of the study to assess behavior and appetite. Participants will also undergo a DEXA scan to assess body composition.


Ages Eligible for Study:   30 Years to 50 Years   (Adult)
Sexes Eligible for Study:   Female
Accepts Healthy Volunteers:   Yes

Inclusion Criteria

  • Body mass index (BMI) between 27 and 40 kg/m2
  • Weight stable for last 2 months
  • Not actively on a weight loss plan
  • No plans to move from the area over the next 2 years
  • Willing to accept random assignment

Exclusion Criteria

  • Pregnant or breastfeeding
  • Within 6 months of giving birth or planning to become pregnant in the next 2 years
  • Diabetes (type 1 or 2) or history of gestational diabetes
  • Renal or liver disease, active neoplasms, or recent myocardial infarction
  • Hyper- or hypothyroidism
  • Lipid lowering medications or medications known to affect weight/energy expenditure
  • Excessive alcohol intake (self-reported, > 3 drinks/day)
  • Postmenopausal, including surgical menopause
  • Currently under psychiatric care or severely clinically depressed (> 17 on Beck Inventory)
  Contacts and Locations
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Please refer to this study by its identifier: NCT00079573

United States, California
Stanford Prevention Research Center
Stanford, California, United States, 94305
Sponsors and Collaborators
National Center for Complementary and Integrative Health (NCCIH)
Community Foundation of Southeastern Michigan
Principal Investigator: Christopher D. Gardner, PhD Stanford University
  More Information

Additional Information:
Publications automatically indexed to this study by Identifier (NCT Number): Identifier: NCT00079573     History of Changes
Other Study ID Numbers: R21AT001098-01A1 ( U.S. NIH Grant/Contract )
Study First Received: March 9, 2004
Last Updated: August 16, 2006

Keywords provided by National Center for Complementary and Integrative Health (NCCIH):
Weight Loss
Premenopausal women

Additional relevant MeSH terms:
Weight Loss
Body Weight Changes
Body Weight
Signs and Symptoms processed this record on August 17, 2017