Adult Weight Management

AWM: Nutrient Adequacy and Caloric Restriction (2013)

Citation:

Gardner CD, Kim S, Bersamin A, Dopler-Nelson M, Otten J, Oelrich B, Cherin R. Micronutrient quality of weight-loss diets that focus on macronutrients: results from the A TO Z study. Am J Clin Nutr. 2010; 92 (2): 304-312.

PubMed ID: 20573800
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The objective of this study was to compare micronutrient intake between overweight or obese women randomly assigned to four popular diets that varied primarily in macronutrient distribution.

Inclusion Criteria:
  • Pre-menopausal overweight or obese women (body mass index, 27kg/m2 to 40kg/m2)
  • Between the ages of 25 and 50
  • Provided written informed consent.
Exclusion Criteria:

Not described.

Description of Study Protocol:
  • Recruitment: Subjects recruited for Stanford's A to Z trial from the local community
  • Design: Randomized trial
  • Blinding used: Implied with measurements.

Intervention

  • Participants were randomly assigned to read and follow one of four diet books that were provided to them: Dr. Atkins New Diet Revolution (2002); Enter the Zone, A dietary roadmap (1995); The Learn Program for Weight Management 2000; or Eat More Weigh Less (2001) by Dean Ornish
  • Each diet group attended eight consecutive one-hour evening classes once per week for eight weeks and was assigned to read approximately one-eighth of their respective books for each class
  • The same registered dietitian led the one-hour class sessions and reviewed the assigned material from the book at each class for all four diets.

Statistical Analysis

  • Differences in the intake of macro-and micronutrients across the diet groups were initially examined by using the non-parametric Kruskal-Wallis test
  • When the null hypothesis was rejected, the Mann-Whitney U-test was further used post hoc to describe the differences for each pair of diet-group comparisons for a given nutrient
  • When the P-value of the ANOVA test for a given nutrient was less than 0.05, exploratory pairwise comparisons were conducted to examine which diets were the most different from each other for continuous variables. Tukey's Studentized range test was used.
  • McNemar's test was used to examine the difference in the proportion of individuals whose risk of inadequate micronutrient intake or prevalence of lower intake (below the AI) changed between baseline and eight weeks within each diet group.
Data Collection Summary:

Timing of Measurements

Measurements made at baseline and at 8 weeks.

Dependent Variables

  • Micronutrient intake: Dietary intake data were obtained by using unannounced 24-hour dietary recalls
    • Dietary recalls were conducted by interviewers trained and certified by the NCC in Minneapolis who were either registered dietitians (RDs) or RD-eligible
    • At each data collection point, three separate, non-consecutive telephone-administered 24-hour dietary recalls were conducted, including two weekdays and one weekend day, whenever possible
  • To assist with portion-size estimates of foods consumed, the study participants were provided with a Food Amounts Booklet that contained estimations tools such as drawings representing wedges, circles, thickness, glasses, mounds, bowls, and portions of meat, chicken and fish
  • The Nutrition Data System for Research (NDS-R) software was used to assess macro and micronutrient intakes
  • Analyses of nutrient intakes were based on food intake alone, without inclusion of dietary supplements.

Independent Variables

  • Participants were randomly assigned to read and follow one of four diet books that were provided to them: Dr. Atkins New Diet Revolution (2002); Enter the Zone, A dietary roadmap (1995); The Learn Program for Weight Management 2000; or Eat More Weigh Less (2001) by Dean Ornish
  • Each diet group attended eight consecutive one-hour evening classes once per week, for eight weeks and was assigned to read approximately one-eighth of their respective books for each class
  • The same registered dietitian led the one-hour class sessions and reviewed the assigned material from the book at each class for all four diets.
Description of Actual Data Sample:

Initial N

311 women enrolled and randomized.

Attrition (Final N)

291 completed the trial (94%)

  • Atkins Group: 73
  • LEARN Group: 73
  • Zone Group: 73
  • Ornish Group: 72.

Age

  • Atkins Group: Mean, 42±5 years
  • Zone Group: Mean, 40±6 years
  • LEARN Group: Mean, 7 years
  • Ornish Group: Mean, 42±6 years.

Ethnicity 

  • Atkins Group: 77% white
  • Zone Group: 67% white
  • LEARN Group: 77% white
  • Ornish Group: 66% white.

Other Relevant Demographics

Not reported.

Anthropometrics

Mean BMI

  • Atkins Group: 32±4
  • Zone Group: 31±3
  • LEARN Group: 31±4
  • Ornish Group: 32±3.

There were no significant differences between groups at baseline.

Location

Stanford, CA.

Summary of Results:

Key Findings

  • At eight weeks, significant differences were observed between groups for all macronutrients and for many micronutrients (P<0.0001)
  • Energy intake decreased from baseline in all four groups but was similar between groups. All four groups reported roughly similar reductions of 500kcal per day relative to baseline
    diets (P=0.76):
    • Atkins: -556±486kcal
    • Zone: -515±506kcal 
    • LEARN: -482±505kcal
    • Ornish: -454±483kcal.
  • At eight weeks, a significant proportion of individuals shifted to intakes associated with risk of inadequacy (P<0.05) in the Atkins Group for thiamine, folic acid, vitamin C, iron and magnesium and in the Ornish Group for vitamins E and B12 and zinc
  • For the Zone Group, the risk of inadequacy significantly decreased for vitamins A, E, K and C (P<0.05) and no significant increases in risk of inadequacy were observed for other micronutrients.
Author Conclusion:

Overall, the findings from this study indicate that public health efforts should be attentive to the overall diet quality of popular weight-loss regimens that focus on altering macronutrient composition and producing weight-loss results.

Funding Source:
Government: NIH grant R21AT1098
Other: Community Foundation of Southeastern Michigan
Reviewer Comments:

Analyses of nutrient intakes were based on food intake alone, without inclusion of dietary supplements.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes