DM: Weight Management (2007)

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

To examine strategies (behavioral therapies, exercise, diet, anorectic drugs, surgery, or a combination of strategies) used for promoting weight loss in people with type II diabetes.

Inclusion Criteria:

(The investigator and 2 consultants, both who were certified diabetes educators independently applied the inclusion criteria)

1. Sample of obese subjects with type 2 diabetes mellitus.

2. A behavioral, dietary, exercise, anorectic drug, surgical or combined strategy to promote weight loss.

3. A measure of weight loss as an outcome of the intervention.

4. The same setting for both treatment and control groups.

5. An ex post facto, one-group pretest-post test, quasiexperimental, or experimental design;

6. Data that permitted calculation for the effect sizes.

Exclusion Criteria:

Duplicate report of the same data.


Description of Study Protocol:


This meta-analysis included studies that used various strategies for weight loss in individuals with type 2 diabetes—behavioral therapies, exercise, diet, anorectic drugs, surgery, or a combination of strategies. Searches were limited to publication dates between 1961 and 1994.

Literature search strategies:

  • Reviewing bibliographies
  • Conducting computer searches
  • Surveying relevant master’s theses
  • Contacting representatives from the Centers for Disease Control



Blinding Used (if applicable):

Not applicable.

Intervention (if applicable):

Coding Procedures:

1. Once studies met inclusion criteria, information was extracted and coded for each of the 80 variables and 23 outcomes.

2. Six quality criteria were applied:

a. type of study design

b. description of sample selection (random vs. convenience)

c. specification of illness or condition with regard to use of replicable diagnostic criteria.

d. completeness of the intervention.

e. clarity of definitions of the outcomes constructs

f. directness and longitudinal nature of outcome measures

Statistical Analysis

(Comparison of studies)

1. Calculation of effect size estimates

2. Homogeneity analyses were calculated for each outcome under each specific strategy.

3. Weighted effect size estimates were pooled for those variables for which primary authors provided sufficient data—age, research design, publication date, quality of the primary study, length of time after the intervention of measurements.

Data Collection Summary:

Timing of Measurements

Dependent Variables:

  • Weight change
  • Metabolic control
  • Lipid metabolism
  • Other physiological measures, e.g. blood pressure

Independent Variables:

  • Behavioral, dietary, exercise, anorectic drug, surgical or combined strategy to promote weight loss
Description of Actual Data Sample:

Initial N: 912 studies

Attrition (Final N): 89 studies involving 1,800 individuals

Age: 52 yr

Ethnicity:  Not mentioned

Other relevant demographics

Anthropometrics: weight, 211 lbs

Location:  Worldwide studies 

Summary of Results:

Other Findings:

The majority (92%) were published since 1980 (1965-1994) in journal articles (90%), a nurse was the primary author in 6.7% and a dietitian was the first author in 1 study.

Intervention Type (%)

  • Dietary 40 %
  • Behavioral 20 %
  • Exercise 10 %
  • Drug, Surgery or Combination strategies 30 %

On average, behavioral interventions involved a series of 10 sessions (range: 1-25), each session meeting for ~78 minutes (range, 22 minutes to 2 hr), 60% of the studies involved group approaches.

Exercise intervention primarily involved aerobic approaches (bicycling, jogging, walking, calisthenics); on average, subjects exercised 4x/week for 50 minutes each.

Dietary interventions primarily involved investigations of ADA wt reduction diets, VLCD or PSMF; both group and individual dietary instructions were used.

Out of a total of a possible score of 21 quality points, the average total quality score was 10, ranging from 5 to 17. Primary reasons that studies received low quality scores were as follows:

  • Lack of randomization
  • Lack of description of intervention, particularly behavioral
  • Lack of direct longitudinal measures of outcome

Diet alone had the most statistically significant impact on weight loss (- 20 lb) and metabolic control (-2.7% in HbA1c)

All diets significantly improved fasting blood sugar.

Behavioral programs alone had a statistically significant impact on weight loss (-6.4 lb) and metabolic control (-1.5%) but effects were less than diet alone.

Behavioral therapy + diet + exercise was associated with a statistically significant effect size estimates for weight loss (-8.5 lb) and metabolic control (-1.6%). However, diet alone achieved better results.

Effects of weight promotion strategies, in general, were smaller in experimental studies and for those >55 years of age.

Author Conclusion:

Dietary strategies were most effective in promoting short-term weight loss in type 2 diabetes in studies reviewed in this meta-analysis.

A number of gaps exist in the current literature—descriptions of subjects, interventions, or longitudinal outcomes beyond 12 months after intervention.

Funding Source:
Government: NIH, NINR
University/Hospital: University of Texas at Austin, University of Texas-Houston Health Science Center
Reviewer Comments:

Well-defined criteria for including studies and systems established for evaluating inter rater reliability.

Impressive decrease in HbA1c with weight loss (-2.7%).

Although the authors used duration of study period as a criteria for evaluating the studies, the mean duration of the studies was not reported.
Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? No
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? Yes
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? Yes
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? Yes
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? Yes
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? Yes
  10. Was bias due to the review's funding or sponsorship unlikely? Yes