|
Promoting weight loss in type II diabetes |
Brown S A, Winter M, Upchurch S, Ramirez G, Anding R |
|
|
Authors' objectives To examine the effectiveness of behavioural therapies, exercise, diet, anorectic drugs, surgery or a combination of strategies in promoting weight loss in people with type II diabetes.
Searching MEDLINE was searched from 1966 to 1994, Combined Health Information Database from 1978 to 1994, Psychological Abstracts from 1967 to 1994, Eric from 1966 to 1994 and Dissertation Abstracts from 1961 to 1994. Masters degree programmes in nursing, public health and dietetics/nutrition were surveyed for relevant theses. Bibliographies of identified studies were checked and contact was made with representatives from the Centres for Disease Control to locate other researchers working in the field of weight loss.
Study selection Study designs of evaluations included in the reviewExperimental studies, quasi-experimental studies, one-group pre-post test studies and ex post facto studies were included.
Specific interventions included in the reviewBehavioural, dietary, exercise, anorectic drugs, surgical or a combined strategy to promote weight loss.
Participants included in the reviewObese adults with type II diabetes were included. The average age was 52 years, weight 211 lb (range: 148 to 314 lb), and 51% were women.
Outcomes assessed in the reviewMeasures of weight loss (body weight, BMI and percentage ideal body weight), metabolic control, lipid metabolism, and other physiological parameters such as blood pressure.
How were decisions on the relevance of primary studies made?The author and two consultants independently applied the pre-defined inclusion criteria to each potentially relevant study. On a random subset of 10 studies, agreement was 92.5%. Disagreements were discussed until consensus was reached.
Assessment of study quality Six quality criteria were applied: type of study design, description of sample selection, specification of illness or condition with regard to the use of replicable diagnostic criteria, completeness of the intervention description, clarity of definitions of the outcome constructs and directness and longitudinal nature of outcome measures. At least two coders applied the criteria independently.
Data extraction At least two coders extracted data independently onto forms developed for data extraction purposes. Any disagreements were discussed until differences were resolved. Studies were coded for descriptive data, methodology, research quality and substantive features.
Methods of synthesis How were the studies combined?The weighted effect sizes were pooled using the procedure of Glass et al. (see Other Publications of Related Interest no.1) and Hedges and Olkin (see Other Publications of Related Interest no.2).
How were differences between studies investigated?Homogeneity analyses were carried out and weighted effect sizes were pooled for participants' ages, research design of the study, publication date, quality of the primary study and length of time after the intervention that measurements were made.
Results of the review Eighty-nine studies with a total of 1,800 participants were included.
Diet alone had the largest statistically-significant impact on weight loss (-20lb) and metabolic control (-2.7% glycosylated hemoglobin). Behavioural therapies alone and exercise alone produced the smallest changes in mean body weight (-6.4 lb and -3.4 lb, respectively) and in metabolic control (-1.5% and -0.8%). The effects were smaller for individuals over the age of 55 years.
Few studies have investigated long-term follow-up (i.e. beyond 6 months). Four studies of diet only showed that measures of mean body weight remained stable during a follow-up period of 31 - 180 days (0.65 =/- 0.49, p<0.05).
Authors' conclusions Dietary strategies are most effective for promoting short-term weight loss in type II diabetes. A number of gaps exist in the extant literature - descriptions of subjects, interventions or longitudinal outcomes beyond 12 months after intervention.
CRD commentary The question, search, inclusion criteria and validity assessment are well-defined. However, the characteristics of individual studies included in the review are not well-documented, although the authors state that a more detailed description is available upon request. The results of this review are based mainly on the findings from non-experimental studies (72% of included studies were of a one-group pre-post test design). Effect sizes were found to be at least twofold larger in one-group studies compared with experimental studies, and only metabolic variables were statistically significant in the experimental studies. Therefore, the authors conclusions about the effectiveness of dietary strategies should be treated with caution.
Funding National Institute for Nursing Research, National Institutes of Health, grant number NR02773.
Bibliographic details Brown S A, Winter M, Upchurch S, Ramirez G, Anding R. Promoting weight loss in type II diabetes. Diabetes Care 1996; 19(6): 613-624 Other publications of related interest 1. Glass GV, McGraw B, Smith ML. Meta-analysis in social research. Beverly Hills (CA): Sage Publications; 1981. 2. Hedges LV, Olkin I. Statistical methods for meta-analysis. New York: Academic Press; 1985. 3. Richter B. Meta-analysis: dietary strategies alone reduce weight best in NIDDM. ACP J Club 1997;126:5.
Indexing Status Subject indexing assigned by NLM MeSH Blood Pressure; Body Weight; Cholesterol /blood; Diabetes Mellitus, Type 2 /blood /physiopathology /therapy; Diet, Diabetic; Diet, Reducing; Exercise; Health Promotion; Humans; Lipoproteins /blood; Longitudinal Studies; Middle Aged; Treatment Outcome; Weight Loss AccessionNumber 11996001033 Date bibliographic record published 30/09/1998 Date abstract record published 30/09/1998 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
|
|
|