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NC: Maintenance of Health/Behavior Change Following Short-term CBT (2008)

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

The purpose of this study was to:

  • determine if modest initial weight losses are associated with better long-term weight losses
  • determine if modest weight loss goals promote better long-term weight losses than larger weight loss goals
  • examine the extent to which weight loss goals and magnitude of initial weight loss affect long-term psychological outcomes
Inclusion Criteria:

69 men and 61 women who participated in a 30-month weight loss study conducted jointly at the University of Pittsburgh and the University of Minnessota who were randomly assigned to a treatment, completed assessments at both baseline and 30 months and attended at least 10 treatment sessions (N=130)

Exclusion Criteria:
Participants in the 30-month weight loss study who did not complete assessments at both baseline or 30 months and/or attend at least 10 treatment sessions  (N=28). The authors reported that those individuals who were included in analyses did not differ from those excluded on any baseline characteristic, including weight loss goals.
Description of Study Protocol:

Recruitment  Little specific information was provided about recruitment procedures. Subjects were participants in a 30-month weight loss study conducted jointly by the University of Pittsburgh and the University of Minnesota.   

Design Program participants were randomly assigned to 1 of 4 active treatment conditions or to a no-treatment control group. Those in active treatment participated for 18 months. No treatment occurred between 18 and 30 months. Participants were weighed and completed questionnaires at baseline and at 6, 12, 18, and 30 months. This study only includes results from those who were assigned to one of the active treatment conditions.

Blinding used (if applicable) None indicated 

Intervention (if applicable) Participants in the 4 active treatment groups obtained behavioral weight loss counseling for 18 months and some also received food, incentives, or both for weight loss and maintenance.  Participants were not told how much weight loss to expect in treatment.   

Statistical Analysis The independent variables (IV) of desired weight loss and maximum achieved weight loss were initially treated as continuous variables and were analyzed with regression analyses with each long-term outcome as dependent variables (DV).  In order to clarify magnitude and pattern of effects, analyses were repeated by dividing each IV into tertiles and conducting categorical analyses. Continuous and categorical analyses produced comparable results, and results cited in study used the categorical approach. Variables considered to be possible covariates included gender, initial treatment group, and baseline values of DV. Gender was significantly related to weight outcomes and thus was included as a covariate in all analyses.

Data Collection Summary:

Timing of Measurements Participants receiving treatment participated in active treatment for 18 months with no treatment contact between 18 and 30 months. Control and treatment group participants were weighed and completed questionnaires at baseline and at 6, 12, 18, and 30 months with baseline questionnaires completed prior to randomization.    

Dependent Variables

  1. Long term weight loss. Baseline weight minus 30-month follow-up weight.
  2. Percentage losing 10% of baseline weight. % of participants whose long-term weight loss exceeded 10% of baseline weight. 
  3. Perceived barriers to adherance (PBA). Was assessed at both baseline and follow-up using a 15-item questionnaire that asked about practical barriers, social barriers, and interpersonal barriers. Barriers were rated using a 5-point scale (1=not at all a problem for me, 5=a very important problem for me), with total score obtained by summing across items.
  4. Eating Behaviors Inventory (EBI) score. EBI, completed at baseline and follow-up, is a 26-item inventory of weight control practices. Higher scores indicate behaviors thought to be associated with successful weight control.
  5. Gormally Binge Eating Scale (BES) score. BES was used only at follow-up to assess tendencies toward binge eating.
  6. Beck Depression Inventory (BDI). BDI was used at follow-up only to measure depressive symptomology. 

Independent Variables

  1.  Maximum Achieved Weight Loss. Difference between baseline weight and lowest weight actually attained at any weekly weigh-in during the first 65 weeks of the study.
  2. Desired Weight Loss. Absolute difference between baseline weight and desired weight.

Control Variables

Gender, initial treatment group, and baseline values of DV when available. 

Description of Actual Data Sample:

Initial N: 160 indivdiuals who were originally randomly assigned to one of the active treatment conditions

Attrition (final N): 130 (69 men and 61 women)

Age: Average of 38 years 

Ethnicity: Not reported

Other relevant demographics: Not reported 

Anthropometrics At entry into the study participants weighed an average of 90 kg (mean BMI=30.9) and wanted to weigh 70 kg (mean BMI=24.0) (e.g., weight loss of about 20 kg or 22% of initial weight).  Participants lost a maximum average of 12.40+ 5.7 lb, 17% achieved their goal weight, maximum weight loss was attained on average at 26.90 +12.2 weeks, and weight loss occurred at an average of 0.51+0.27 kg/week. Only 15% of participants reached their personal weight loss goal.  

Location: The study was conducted jointly at the University of Pittsburgh and the Unviversity of Minnesota.

 

Summary of Results:

EFFECTS OF ACHIEVED WEIGHT LOSS ON 30-MONTH OUTCOME

  1. Participants were divided into 3 tertiles based on maximum achieved weight loss: tertile 1 lost an average of 6.2 kg (range -0.3-9.1), tertile 2 lost an average of 12.5 kg (range 9.2-15.2), and tertile 3 lost an average of 18.5 kg (range 15.4-30.2). The 3 tertiles were not significantly different in baseline BMI which ranged from 30.3-31.4. 
  2. It took tertile 3 (with highest maximum weight loss) a significantly longer time (31.3 weeks, P<0.02) to achieve maxumum weight loss compared to the other 2 tertiles. However, tertile 3 lost weight at a significantly faster rate than the other 2 tertiles (P<0.001), with tertile 3 losing weight at over twice the rate of those in tertile 1. Thus, speed of rate loss (rather than duration of weight loss) was the primary factor contributing to maximum weight loss. Thirty percent of participants in tertile 3 reached their goal weight, compared to 21% and 0% in tertiles 2 and 3, respectively (P<0.001). 
  3. Weight loss at 30 months favored those who lost the most weight, with tertile 3 attaining significantly greater weight loss (6.4 kg) than tertiles 2 (1.9 kg) and 1 (-2.5 kg) (P<0.0001).  A larger percentage of participants in tertile 3  (23%) lost at least 10% of baseline weight compared to 9% and 2% of those in tertiles 2 and 1, respectively (P<0.008).
  4. Psychological outcomes (EBI score, PBA, BDI, BES score) at 30 months did not differ significantly among the 3 tertiles. Thus, initial weight losses (and greater weight regains) did not produce negative psychological effects.  

EFFECTS OF DESIRED WEIGHT LOSS ON 30-MONTH OUTCOME

  1. The participants were divided into 3 tertiles according to amount of desired weight loss at baseline: tertile 1 desired weight loss of 14.3 kg (range 8.3-17.5), tertile 2 desired 20.0 kg weight loss (range 17.6-27.6), and tertile 3 desired 26.0 kg weight loss (range 22.8-33.2). Initial BMIs were 29.0, 31.0 and 32.6 in tertiles 1, 2, and 3, respectively, and participants with higher initial BMIs had significantly higher weight loss goals (P<0.0001). Mean weight losses were 2.9 kg, 0.4 kg and 2.2 kg in tertiles 1, 2, and 3 respectively, at 30 months.
  2. Desired weight loss goal was:
  • significantly related to the likelihood of reaching weight loss goals, with 41% of tertile 1 attaining their weight loss goal compared to 5% in tertiles 2 and 3 (P<0.001).
  • not predictive of initial weight loss, weight loss at 30 months, psychological outcomes at 30 months, weight regain after maximum loss, or percentage of participants who maintained a 10% reduction from initial body weight at 30 months.   

Other Findings

  1. Closeness to attaining weight goals in treatment did not predict long-term weight change of psychological variables.
  2. Men who reached their weight goals (n=19) weighed less at baseline (92.3 kg vs. 98.1 kg) ( P<0.001), had lower weight loss goals (17.5 kg vs. 20.9 kg) (P<0.001), had better short-term weight losses (17.2 kg vs. 12.7 kg) (P<0.002) and better long-term weight losses (5.4 kg vs. 1.6 kg) (P<0.03) than those who did not reach weight goals (women were not included in analyses because only 3 women reached their weight loss goal).
Author Conclusion:
  1. Weight loss goals did not predict short- or long-term weight loss or long-term psychological outcomes. Participants with modest goals were more likely to achieve their goals. Overall, these findings do not support the idea that interventions aimed at altering the weight loss goals of obese patients could dramatically improve long-term results.  
  2. Participants who initially lost more weight regained more weight and at a more rapid rate compared to those who initially lost less weight.  Even so, at 30 months participants who lost large amounts of weight maintained a greater proportion of weight loss, had larger net weight losses, and were more likely to remain 10% below their baseline body weights compared to other participants. Overall, these findings did not support the belief that smaller initial losses would lead to better weight loss results. 
  3. Psychological well-being at 30 months was not related to initial weight losses or weight loss goals.
Funding Source:
Government: NHLBI
Reviewer Comments:
  1. No specific information was provided in regard to how participants were recruited for study. 
  2. No information was provided about ethnicity and other demographic variables besides age.
  3. Little information was provided about the exact behavioral treatment used with participants in this study.
  4. It appears there is a typographical error in Table 2: "% losing <10% of baseline weight" should instead read "% losing > 10% of baseline weight."
  5. Weight loss goals in this study were based on participants' reports of what they would like to weight, rather than on their expectations for weight loss in this particular intervention. Thus, the weight loss goal may not be entirely reflective of participants' desired weight loss in this specific program.
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? ???
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? ???
  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? Yes
  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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
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? 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? N/A
  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? Yes
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