DM: Weight Management (2007)

Citation:

Norris SL, Zhang X, Avenell A, Gregg E, Bowman B, Serdula M, Brown TJ, Schmid CH and Lau J. Long-term effectiveness of lifestyle and behavioral weight loss interventions in adults with type 2 diabetes: a meta-analysis. Am J Med 2004 Nov 15;117(10):762-74.

PubMed ID: 15541326
 
Study Design:
Meta-analysis or Systematic Review
Class:
M - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
The purpose was to assess effectiveness of lifestyle and behavioral interventions in promoting weight loss among adults with type 2 diabetes.
Inclusion Criteria:

Data Sources:

  • electronic searches included Medline, EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Educational Resources Information Center (ERIC), PsychInfo, Web of Science, Biosis, Nutrition Abstracts and Review, Cochrane Library, and Cochrane Register of Controlled Trials.
  • hand searched relevant journals including Diabetes Care, International Journal of Obesity and Related Metabolic Disorders, Obesity Research, American Journal of Clinical Nutrition and Journal of the American Dietetic Association
  • Attempted to contact authors if data were unclear or missing.

Study Selection

  • published and unpublished RCT in any language that examined weight loss or weight control trials involving dieting, physical activity or behavioral interventions
  • subjects were adults > 18 years of age with type 2 diabetes, recorded body weight or BMI, and follow-up interval of >12 months.
Exclusion Criteria:
  • studies of < 12 months duration
Description of Study Protocol:

Recruitment: not applicable

Design: Systematic review protocol using the Cochrane Collaboration Method

Blinding used: not applicable

Intervention: not applicable

Statistical Analysis:

  • based on 22 eligible studies in 21 publications
  • meta-analysis to combine continuous data when two or more studies reported an outcome of interest
  • pooled effects determined using DerSimonian and Laird random-effects model; the three groups of studies were:
    • any intervention versus usual care
    • very low-calorie diet versus low-calorie diet
    • physical activity versus no or less intensive physical activity
  • meta-regression to determine if study-level characteristics affected between-group change in weight
  • heterogeneity examined using chi-squared test
Data Collection Summary:

Timing of Measurements: Two reviewers independently abstracted relevant demographic and intervention characteristics. They reached consensus through discussion.

 Dependent Variables

  • weight loss
  • percentage of baseline weight lost (based on individual data)
  • body mass index
  • fasting blood glucose
  • glycated hemoglobin (HbA1c)
  • blood pressure
  • lipid concentrations

Independent Variables

  • dietary (low calorie diets of 800 to 1500 kcal/day or very low calorie diets (<800 kcal/day).
  • physical activity (involved specific approach to increasing activity levels such as counseling, exercise prescription or participation in supervised or unsupervised exercise program)
  • behavior therapy (addressed barriers to diet or physical activity; used strategies such as social support or stimulus control)

Control Variables

 

Description of Actual Data Sample:

Initial N: 22 studies with 4659 subjects (range 20 to 2205 participants per study)

Attrition (final N): 0 to 30%; completion rate was < 80% in five studies

Age: mean age 55 years

Ethnicity: not described

Other relevant demographics: mean duration of diabetes 6.5 years

Anthropometrics

Location:  worldwide studies 

 

Summary of Results:

 

Weight Loss by Pooled Groups

Comparison Number of Studies Number of Subjects Weight Loss 95% CI
Any intervention vs Usual Care

7

585

1.7 kg

 

Very low calorie diet vs low-calorie diet

2

126

3.0 kg

-0.5 to 6.4 kg

Physical activity vs no or less intensive physical activity

2

53

3.9 kg

-1.9 to 9.7 kg

 

Weight Change for Single Study Arms

Intervention

Number of Studies

Number of Subjects at Follow-up

 Weight Change 95% CI (kg)

P Value for Heterogeneity

Usual care

7

564

-2.0 (-3.5 to -0.6)

0.05

Low-calorie diet

12

917

-3.7 (-5.1 to -2.3)

<0.0001

Low-calorie diet

 3

232 

-1.8 (-3.2 to -0.3) 

0.61

Low-calorie diet, behavioral intervention

2

53

-4.0 (-7.2 to -0.7)

1.0

Low-calorie diet, physical activity, behavioral intervention

 13

485 

 -4.1 (-5.4 to -2.9)

0.10

Very low-calorie diet, physical activity, behavioral intervention

2

126

-7.7 (-9.8 to -5.5)

0.55

 Other Findings

Changes in HbA1c generally corresponded to weight loss; between-group differences were not significant.

Author Conclusion:
Multi-component weight loss strategies involving diet, physical activity and behavioral interventions may help overweight adults with type 2 diabetes lose weight.
Funding Source:
Government: CDC
Reviewer Comments:
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? N/A
 
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