Authors' objectives

To review the literature on the long-term results of weight loss in the non-insulin-dependent diabetes mellitus (NIDDM) population.

Searching

MEDLINE, CINAHL and PsycINFO were searched from 1985 using the terms 'non-insulin-dependent diabetes mellitus' combined with 'weight loss' or 'diet'. Reference lists of retrieved articles were searched for additional references, including those before 1985. Two experts in the field were asked to review the list of retrieved articles to identify if any key articles were missing.

Study selection

Assessment of study quality

The quality of relevant studies was assessed using criteria based on those of Sackett and Haynes (see Other Publications of Related Interest). Criteria assessed included sample size and power, method of allocation, method of outcome measurement, and length and level of follow-up achieved. An overall rating of strong, moderate or weak was assigned to each article. 'Weak' studies were excluded. The authors do not state how the papers were assessed for quality, or how many of the authors performed the quality assessment.

Data extraction

The authors do not state how the data were extracted for the review, or how many of the authors performed the data extraction.

Methods of synthesis

Results of the review

Twenty-three studies were included. The results from the 13 studies with a strong or moderate rating (585 participants) were included in the review, whereas those from 10 weak studies were not.

Six studies were rated as strong and 4 as moderate.

1. Behavioural or educational strategies (8 studies).

Weight loss was reported in most of the behaviour modification interventions, but in some trials the weight loss in these groups was not significantly different from other interventions. Weight loss was more likely to be significant in those trials with a shorter follow-up period than in those trials with a longer one. Similar results were also reported for other variables such as glucose, haemoglobin A and insulin levels.

2. VLCDs (3 studies).

In one trial, short-term improvements in glycemic control and normalised fasting glucose levels were seen, but relapse occurred in most patients when followed to 19 months. In another trial (behaviour modification intervention plus or minus VLCD in one arm), no significant differences in weight loss were seen at one year (6.8 to 8.6 kg) or in fasting glucose levels. In the third trial (a before-and-after study with only 10 patients), decreases were reported in body weight, triglycerides, blood-pressure and fasting glucose.

Authors' conclusions

Weight loss and subsequent improved metabolic control are achieved, but not maintained, by most participants.

CRD commentary

The review has clear inclusion criteria and a discussion of the limitations of the primary studies. An assessment of quality is made, and the results from poor quality trials are not reported in any detail. Due to the heterogeneity of the interventions, the results are reported descriptively, which is appropriate. The search strategy is reasonable, but it is unclear why the electronic searches were limited to post-1985 studies. Furthermore, no attempt was made to locate unpublished trials, so it is possible that some important trials may have been missed. It would have been useful to have had more details of the methodology of the review, such as the decisions for including the primary studies or how the studies were graded moderate or strong for quality; details on the study setting and the characteristics of the study participants would also have been welcome. The authors' conclusions are supported by the available evidence.

Implications of the review for practice and research

The authors state that there is a need for prospective trials of weight loss with longer follow-up. Further study of predictors of success in the subgroup who are able to maintain weight loss, would be highly useful, e.g. to determine the most appropriate treatment combinations for improving weight maintenance and metabolic parameters in obese patients with NIDDM.

Bibliographic details

Ciliska D, Kelly C, Petrov N, Chalmers J. A review of the weight loss interventions for obese people with non-insulin-dependent diabetes mellitus. Canadian Journal of Diabetes Care 1995; 19(2): 10-15.

Other publications of related interest

Sackett DL, Haynes RB, Tugwell P. Clinical Epidemiology. Toronto: Little, Brown and Company; 1985.

Indexing Status

Subject indexing assigned by CRD

MeSH

Diabetes Mellitus; Diabetes Mellitus, Type 2; Weight Loss

AccessionNumber

11997005275

Database entry date

31/12/1999

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.