NC: Weight Management (2007-2008)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To evaluate the independent and combined contributions of cognitive therapy and nutrition education as additions to a standard behavioral intervention for weight loss.

Inclusion Criteria:
  • Weight of at least 15% more than the highest weight in the range for their height and body frame size
  • Obtained written medical consent
  • $50 deposit, refundable contingent upon completion of homework assignments and attendance at follow-up assessments.
Exclusion Criteria:
  • Current treatment for obesity
  • Demonstration of bulimic behavior
  • Usage of medication that affects water retention, appetite or metabolism
  • Pregnancy.
Description of Study Protocol:
  • Recruitment: Via announcements in a faculty-staff newsletter of a large state university, in a local newspaper and on a public cable television station
  • Design: Factorial contructive design. Subjects were blocked on gender and percentage overweight and randomly assigned within stratified blocks to one of four interventions.


Four intervention conditions:

  • Behavior therapy plus cognitive therapy (BT+CT)
  • Behavior therapy plus nutrition education (BT+NE)
  • Behavior therapy plus cognitive therapy and nutrition education (BT + CT + NE)
  • Behavior therapy (BT).

BT was common to all intervention conditions, which allowed the separate contributions of cognitive therapy and nutrition education and their combined effects to be assessed.

  • Behavior Therapy (BT)
    • Behavioral homework was required, checked weekly and subjects refunded a portion of their deposit for completing homework assignments
    • Treatment sessions included private weekly weigh-in on a digital scale
    • Participants were given a self-report Behavior Questionnaire (BQ) to assess frequency of specific eating behaviors.
  • Cognitive Therapy (CT)
    • Identification and modification of cognitive attributions that affect weight loss
    • The Hopelessness, Motivation and Physical Attribution subscales of the Master Quesionnaire (MQ) were used as the basis of cognitive intervention
    • Each participant received individualized printed feedback, indicating alternative ways of thinking for those questions answered incorrectly on pre-treatment responses on the MQ
    • Group discussion format used, based on participants' responses to MQ items
    • New information and adaptive self-statements presented and practiced in each session
    • The Eating Self-Efficacy Scale (ESES) was used to provide information about the relationship between self-efficacy and weight control
    • A Negative Thoughts About Weight Questionnaire (NTWQ) was designed to assess specific thoughts about losing weight.
  • Nutrition Education (NE)
    • Computer analysis of daily diet and two meetings with registered dietitians
    • Participants input, weekly, the food-eaten information using the EATS computer program
    • If any nutrient requirements were not met, information about possible sources of the nutrient were provided.
  • Treatment Credibility Ratings
    • Subjects rated their expectations for success in the program (to examine differential expectations for success between treatment conditions). 

Statistical Analysis

Repeated-measures MANOVA used to test the effects of CT and NE at four assessment periods, guided by four hypotheses:

  1. There would be no significant differences between treatment conditions on physiological measures of obesity (weight, body fat)
  2. All treatment conditions would show significant differences across time on behavioral measures
  3. Groups which received a cognitive intervention would demonstrate a greater change on cognitive measures related to weight
  4. Groups which received nutrition education would demonstrate a greater change on measures of nutritional adequacy.
Data Collection Summary:

Timing of Measurements

There were four assessment periods (pre-test, post-test, three-month follow-up and six-month follow-up) for all but food diaries (pre-test and post-test only).

Dependent Variables

Hypothesis One

  • Weight (digital scale)  
  • Body fat percentage (determined from four sites on the body: Triceps, biceps, subscapula, suprailiac skinfolds)
  • Feinstein weight-reduction quotient (WRQ; accounts for height, weight, degree overweight, weight-reduction goals and number of pounds lost).

Hypothesis Two

  • Behavioral Questionnaire (BQ) scale (a mean behavior technique usage percentage was calculated by averaging the rating of percentage of time used for each technique)
  • Master Questionnaire (MQ) Stimulus Control scale.

Hypothesis Three

  • Master Questionnaire (MQ) Hopelessness, Motivation and Physical Attribution scales
  • Negative Thoughts About Weight Quesionnaire (NTWQ) score
  • Negative Affect and Social Acceptability scales of the Eating Self-Efficacy Scale (ESES).

Hypothesis Four

Calories, percentage of protein, carbohydrates, fat, alcohol, percentage of RDAs of vitamin A, thiamine, riboflavin, vitamin C, vitamin D, fiber, cholesterol.

Independent Variables

  • Treatment conditions (BT, BT+CT, BT+CT+NE, BT+NE) 
  • Assessment periods (pre-test, post-test, three-month follow-up, six-month follow-up). 

Control Variables


Description of Actual Data Sample:
  • Initial N: 69 (60 women, nine men)
  • Attrition (final N): 57 (17.4%)
  • Mean age: 40.68 years
  • Ethnicity: Not mentioned
  • Other relevant demographics: None
  • Anthropometrics
    • Mean weight: 185.37lbs
    • Mean number of pounds overweight: 50.25; averaged 36.90% overweight.
  • Location: USA.
Summary of Results:

Results of Repeated-Measures MANOVA to Test the Effects of CT and NE at Four Assessment Periods

Hypothesis One

There would be no significant differences between treatment conditions on physiological measures of obesity (weight, body fat).

  • Significant time main effect for both weight F(3,38)=17.74, P<0.0001 and body fat F(3,33)=4.43, P<0.01
    • For weight, there were significant differences between pretest and other assessments.
    • For body fat, there were significant differences between pretest and 3-month follow-up.

Hypothesis Two

All treatment conditions would show significant differences across time on behavioral measures

  • Significant time main effect for BQ and MQ Stimulus Control, F(3,34)=45.28, P<0.0001
    • For BQ, there were significant differences for all comparisons of the means
    • For Stimulus Control, there were significant differences between pre-test and all other assessments. 

Hypothesis Three

Groups which received a cognitive intervention would demonstrate a greater change on cognitive measures related to weight

  • Significant time main effect for MQ Hopelessness, Motivation and Physical Attribution scales, the NTWQ and the Negative Affect and Social Acceptability scales of the ESES F(3,36)=14.05, P<0.0001
    • For all cognitive measures, there were significant differences between pre-test and other assessments.
  • Significant cognitive main effect for MQ Hopelessness, Motivation and Physical Attribution scales, the NTWQ, and the Negative Affect and Social Acceptability scales of the ESES F(24, 15)=2.56, P<0.05
    • For Motivation, there were significant interactions between CT and time at every assessment period (higher levels of motivation in CT groups)
    • For Physical Attribution, there were significant interactions between CT and time at all assessment periods, except post-test (less physical attribution for inability to lose weight in CT groups).

Hypothesis Four

Groups which received nutrition education would demonstrate a greater change in measures of nutritional adequacy

  • MANOVA: Number of calories, percentage of protein, percentage of carbohydrates, percentage of fat, percentage of alcohol DVS
  • Significant time main effect F(1,32)=12.90, P<0.001
    • All treatment conditions changed significantly on nutritional measures over time
    • For calories, percentage of protein and percentage of carbohydrates, there were significant differences.

Other Findings

  • All subjects lost a statistically significant amount of weight, but weight-loss was less than has been reported from other behavioral weight control programs and no differences between the treatment groups were found 
  • Subjects in cognitive groups developed more adaptive cognitions about weight-loss and continued to lose weight through the six-month follow-up.
Author Conclusion:
  1. Because CT was successful in modifying cognitions concerning weight and weight-loss, perhaps 10 weeks of behaviorally-oriented treatment, followed by 10 weeks of cognitive intervention would produce better results
  2. It has not been demonstrated that nutrition information facilitates weight loss, so nutrition education may not be necessary for some people (in other words, some people may already have good nutrition knowledge but fail to use it).  An assessment of pre-treatment nutritional knowledge could be used to assign individuals with a lack of accurate nutritional informaiton to a nutritional intervention.
  3. Failure to assess and provide the additional components that each individual subject needs may explain the lack of statistical significance between groups. Differential diagnosing is necessary to advance the weight-control field.
  4. Ten weeks of treatment is not sufficient to produce significant change and weight loss.
  5. Treatment overload (BT+CT+NE) may have impacted the outcome (this group loss less weight than other groups)
  6. Cognitive and nutritional interventions may not be powerful treatments for obesity, at least as implemented in this study
  7. Changes in cognition about weight and weight loss may occur with or without cognitive intervention, but behavior change seems to be a strong determinant of change in cognitions.
Funding Source:
University/Hospital: Purdue University, John Hopkins University
Reviewer Comments:


  1. Subjects were blocked on gender and percentage overweight and randomly assigned within stratified blocks to one of four treatment interventions
  2. Nutrition education provided by registered dietitians.


Authors report that 57 subjects completed the study, yet various Ns less than 57 were reported in the statistical analysis summary table in the article. One assumes that data was missing for many of the subjects, but there was no discussion of this.

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? No
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.) Yes
  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? No
  4.4. Were reasons for withdrawals similar across groups? ???
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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.) N/A
  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? No
  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? N/A
  6.6. Were extra or unplanned treatments described? N/A
  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? ???
  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