title: Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial.
abstract: BACKGROUND
  Popular diets, particularly those low in carbohydrates, have challenged current recommendations advising a low-fat, high-carbohydrate diet for weight loss. Potential benefits and risks have not been tested adequately.
  
  
  OBJECTIVE
  To compare 4 weight-loss diets representing a spectrum of low to high carbohydrate intake for effects on weight loss and related metabolic variables.
  
  
  METHODS
  Twelve-month randomized trial conducted in the United States from February 2003 to October 2005 among 311 free-living, overweight/obese (body mass index, 27-40) nondiabetic, premenopausal women.
  
  
  METHODS
  Participants were randomly assigned to follow the Atkins (n = 77), Zone (n = 79), LEARN (n = 79), or Ornish (n = 76) diets and received weekly instruction for 2 months, then an additional 10-month follow-up.
  
  
  METHODS
  Weight loss at 12 months was the primary outcome. Secondary outcomes included lipid profile (low-density lipoprotein, high-density lipoprotein, and non-high-density lipoprotein cholesterol, and triglyceride levels), percentage of body fat, waist-hip ratio, fasting insulin and glucose levels, and blood pressure. Outcomes were assessed at months 0, 2, 6, and 12. The Tukey studentized range test was used to adjust for multiple testing.
  
  
  RESULTS
  Weight loss was greater for women in the Atkins diet group compared with the other diet groups at 12 months, and mean 12-month weight loss was significantly different between the Atkins and Zone diets (P<.05). Mean 12-month weight loss was as follows: Atkins, -4.7 kg (95% confidence interval [CI], -6.3 to -3.1 kg), Zone, -1.6 kg (95% CI, -2.8 to -0.4 kg), LEARN, -2.6 kg (-3.8 to -1.3 kg), and Ornish, -2.2 kg (-3.6 to -0.8 kg). Weight loss was not statistically different among the Zone, LEARN, and Ornish groups. At 12 months, secondary outcomes for the Atkins group were comparable with or more favorable than the other diet groups.
  
  
  CONCLUSIONS
  In this study, premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake, lost more weight at 12 months than women assigned to follow the Zone diet, and had experienced comparable or more favorable metabolic effects than those assigned to the Zone, Ornish, or LEARN diets [corrected] While questions remain about long-term effects and mechanisms, a low-carbohydrate, high-protein, high-fat diet may be considered a feasible alternative recommendation for weight loss.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00079573.
authors.affiliation: Stanford Prevention Research Center and the Department of Medicine, Stanford University Medical School, Stanford, Calif, USA. cgardner@stanford.edu
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Gardner
authors.forename: Alexandre
authors.initials: A
authors.lastname: Kiazand
authors.forename: Sofiya
authors.initials: S
authors.lastname: Alhassan
authors.forename: Soowon
authors.initials: S
authors.lastname: Kim
authors.forename: Randall S
authors.initials: RS
authors.lastname: Stafford
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Balise
authors.forename: Helena C
authors.initials: HC
authors.lastname: Kraemer
authors.forename: Abby C
authors.initials: AC
authors.lastname: King
mesh_terms: D000328:Adult; D001786:Blood Glucose; D001794:Blood Pressure; D015992:Body Mass Index; D004033:Diet Fads; D004038:Diet, Reducing; D004040:Dietary Carbohydrates; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008055:Lipids / Q000097:blood; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000178:diet therapy*; D050177:Overweight; D017697:Premenopause; D012307:Risk Factors; D015431:Weight Loss
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D008055:Lipids