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Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease


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Title: Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease

Comparison of the Atkins, Ornish, Weight
Watchers, and Zone Diets for Weight Loss and
Heart Disease Risk Reduction A Randomized Trial
  • Melody Lee, MD
  • UCSF Family and Community Medicine
  • Journal Club
  • January 21, 2005

Introduction Context
  • Obesity has become an epidemic

Introduction Context
  • Popular diets have become increasingly prevalent
    and controversial
  • Patients and clinicians are interested in using
    popular diets for disease prevention
  • However, there is little data regarding the
    relative benefits, risks, effectiveness and
    sustainability of popular diets

Comparison of the Atkins, Ornish, Weight
Watchers, and Zone Diets for Weight Loss and
Heart Disease Risk Reduction A Randomized Trial
  • Michael L. Dansinger Joi Augustin Gleason John
    L. Griffith Harry P. Selker Ernst J. Schaefer
    JAMA. Jan 5, 200529343-53.

  • Assess the effectiveness of four popular diets
    for weight loss and cardiac risk factors, and to
    assess self-reported adherence rates to each diet

Study description
  • Single-center one-year randomized trial at an
    academic center in Boston, Mass
  • Enrolled July 2000- January 2002

Methods Inclusion Criteria
  • Adults with BMI between 27 and 42
  • At least one of the following metabolic risk
  • Fasting glucose 110mg/dL
  • Total cholesterol 200 mg/dL
  • LDL cholesterol 130 mg/dL
  • HDL cholesterol
  • Triglycerides 150 mg/dL
  • SBP 145 or DBP 90
  • Or current use of oral medications to treat HTN,
    DM, or dyslipidemia

Methods Exclusion Criteria
  • Unstable chronic illness
  • Insulin therapy
  • Urinary microalbumin 2 times normal
  • Serum creatinine 1.4mg/dL
  • Clinically significant LFT or TFT abnormalities
  • Weight loss medication
  • Pregnancy

Methods Participants
  • Recruited in Greater Boston area via newspaper
    advertisements, television publicity
  • 1010 screened via telephone (513 not interested
    or too busy)
  • 247 screened in person (22 no risk factors, 14
    too busy, 13 diets too extreme)
  • 160 final participants
  • 40 participants randomized to each diet group

Methods Randomization
  • Participants chose 1 of 4 class times
  • Once approximately 10 participants per class
    time, 1 of 4 diets were assigned to the small
    group by according to computer-generated
    randomized Latin square sequence
  • Each diet was assigned to each class time only
    once per cycle x 4 cycles

Methods Blinding
  • Study personnel blinded to dietary assignment
    until after small group roster finalized to avoid
    recruiting bias
  • Diet assignment was revealed to small group at
    first meeting and participants were given diet
    specific rationale, written materials, and
    official diet cookbook
  • Lab personnel were blinded

Methods Intervention
  • One of four popular diets Atkins, Zone, Weight
    Watchers, or Ornish
  • Only dietary components, not other aspects that
    may be unique to dietary program

Methods Dietary Intervention
  • Less than 20 g of carbohydrate daily with a
    gradual increase to 50 g daily
  • 40-30-30 balance of percentage calories from
    carbohydrate, fat, and protein respectively

Methods Dietary Intervention
  • Keep total daily points in a range determined
    by current weight. Each point 50 calories.
    Participants roughly aimed for 24-32 points
    daily. Point values for certain food provided
    through diet
  • Vegetarian diet containing 10 calories from fat

Methods Standard Intervention
  • Standard recommendation daily MVI, 60 minutes of
    exercise weekly, avoid commercial support
  • A dietician and physician met with each small
    group for 1 hour on 4 occasions during the first
    2 months of study
  • Subsequent meetings aimed to maximize adherence
    by reinforcing positive changes and addressing
    barriers to adherence
  • After 2 months, participants were encouraged to
    follow their assigned diet according to their

Methods Outcomes
  • Participants were blinded to timing of
    assessments until 2 weeks prior
  • Three main outcomes were studied
  • Weight loss
  • Cardiac risk factors
  • Adherence

Methods Determining Weight Loss
  • Baseline weight taken 2 weeks prior to dietary
    intervention, subsequent weight assessed using
    same scale with light clothing and no shoes

Methods Determining Cardiac Risk Factors
  • Overnight fast
  • Total cholesterol
  • HDL cholesterol
  • Triglycerides
  • Glucose
  • Insulin
  • High sensitivity C-reactive protein
  • Creatinine
  • Friedewald formula for LDL cholesterol
  • 24-hour urine for total protein, nitrogen and

Methods Determining Adherence
  • Submitted 3-day food records at 1,2,6 and 12
    months were entered into computer program that
    calculated average daily macronutreints and
    micronutrients and adherence was scored on a 10
    point scale (0baseline to 10perfect adherence)
  • Self report of adherence in past 30 days using
    same scoring system

Methods Analysis
  • Standard statistical analysis
  • The assumption was made that participants who
    discontinued the study were unchanged from
  • Investigators examined the data twice (1) with
    the missing data substituted by baseline values
    (2) with the missing data excluded

Results Participants
  • The 40 participants in each diet group were
    similar in terms of baseline characteristics
  • At baseline there was no significant differences
    in caloric or macronutrients between diet groups
  • Mean age 49, range 22-72
  • 81/160 women

Results Attrition and AEs
  • Attrition was 21 at 2 months, 38 at 6 months
    and 42 at 12 months
  • At 12 months, there was a nonsignificant trend
    (P0.08) toward a lower continuation rate for
    more extreme diets (Atkins and Ornish) compared
    to moderate diets (Zone and Weight Watchers)
  • The most common reasons for discontinuation was
    (1) assigned diet was too difficult or (2) not
    yielding enough weight loss
  • No adverse events

Results Weight Loss
  • All 4 diets resulted in statistically
    significant, albeit modest, weight loss at 12
  • There was not a statistically significant
    difference between the diets
  • Greater effects were observed in study completers
  • 25 of initial participants lost 5 of initial
    body weight, 10 of participants lost 10 or more

Results Weight Loss
Results Dietary Intake
  • At one year, the mean daily caloric reduction
    from baseline was 138 for Atkins, 251 for Zone,
    244 for Weight watchers and 192 for Ornish (pall groups and p0.70 between diets)

Results Weight Loss Associated with Adherence
  • There was a strong curvilinear association
    between self-reported dietary adherence and
    weight loss (r0.60 p
  • Participants in the top tertile of adherence lost
    7 of body weight on average

Weight loss by diet type and weight loss by
dietary adherence
Results Cardiac Risk Factors
  • All diets achieved modest, but statistically
    significant improvements in several cardiac risk
    factors at 1 year
  • No diets significantly altered triglycerides,
    blood pressure, or fasting glucoses at 1 year

Results Cardiac Risk Factors
Statistically significant
Results Weight loss associated with
improvement of cardiac risk factors
  • The amount of weight loss predicted the amount of
    improvement in several cardiac risk factors
    Total/ HDL cholesterol ratio (r-0.36),
    C-reactive protein (r-0.37), and Insulin levels

Cardiac risk factors as a function of weight loss
Results Adherence
  • Dietary adherence per 3-day diet records and self
    report decreased progressively with time
  • Approximately 25 of participants in each diet
    group sustained a mean adherence level of at
    least 6-10

Mean Self-reported Dietary Adherence Scores of
All 4 Diet Groups
Results Exercise
  • Exercise levels per self-report (minimal, mild,
    moderate, vigorous) increased from baseline
    throughout the trial (pbetween diets
  • No significant association between change in
    exercise and either weight loss or cardiac risk
    factor improvement

Study Conclusions
  • A variety of popular diets can reduce weight and
    cardiac risk factors under realistic conditions,
    but only for the most adherent
  • Sustained adherence to a diet rather than diet
    type was the key predictor of weight loss and
    cardiac risk factor reduction

Discussion Is this study relevant?
  • Q Can I apply it to my clinic population?
  • A Probably. The participants in this study are
    not medically dissimilar to patients in our
    clinics and the study is realistic. However,
    participants who called likely more motivated
    than typical patient. Study did not report SES,
    language, ethnicity, etc.

Discussion Is this study relevant?
  • Q Are the likely benefits worth the potential
    harms and cost?
  • A Probably. Obesity has been shown to increase
    morbidity and mortality and even modest weight
    loss has benefit. No obvious harm in the short
    term. Long term has not been studied. Also, does
    being on a diet decrease quality of life?

Discussion Is this study relevant?
  • Q Were all the clinically important outcomes
  • A Possibly. Besides weight loss and cardiac
    risk factors which have been shown to decrease
    morbidity and mortality, investigators could have
    examined quality of life. Mortality was beyond
    the scope of this study.

Discussion Is this study valid?
  • Q Was the assignment of participants to
    intervention random?
  • A Yes, a computer generated a diet to each
    small group and at only one of 4 meeting times

Discussion Is this study valid?
  • Q Was follow up complete?
  • A No. This study drop out rate was large at 42
    (consistent with dropout rates in other diet
    studies). Data was analyzed with the assumption
    was that those who discontinued would be back to
    baseline and missing data was substituted with
    baseline. This is a very conservative measure.
    Results were consistent when missing data was
    excluded entirely from the analysis

Discussion Is this study valid?
  • Q Were patients analyzed in the groups to which
    they were randomized?
  • A Yes, this study followed the intention to
    treat principle

Discussion Is this study valid?
  • Q Were participants, clinicians and personnel
    blinded to the intervention?
  • A No, participants and providers knew which diet
    they were assigned by the first meeting, which
    could have affected outcomes depending on
    expectations, biases. (those optimistic about the
    diet theyve been assigned may do better) Only
    the lab personnel was blinded, the person least
    likely to affect outcome.

Discussion Is this study valid?
  • Q Were the groups similar at the start of the
  • A Yes demographically, as well as by baseline
    weight, caloric intake and cardiac risk factors

Discussion Is this study valid?
  • Q Were the groups treated equally apart from
    their intervention?
  • A Maybe. Investigators standardized their
    recommendation for daily MVI, 60 minutes of
    exercise/ week, and avoiding commercial support.
    However they did give each participant the
    corresponding literature and cookbooks, which are
    different from one another. Also, there was no
    mention of standardized small group meeting
    content or structure

Discussion What are the results?
  • Q How large and precise was the treatment
  • A Results were only modest in weight loss and
    improvement in cardiac risk factors, but
    statistically significant.

  • What if you just held the meetings and followed
    weight and cardiac risk factors?
  • How accurate is the data? Diet records usually
  • How real is the adherence score? It may be all

  • What advice would I give to patients who want to
    lose weight? Tell them to just pick the diet
    that you think will work for you and stick to it?
  • Would I recommend a diet based on a patients
    cardiac risk factors?
  • How can I encourage dietary adherence?