Effectiveness of lifestyle-based weight loss interventions for adults with type 2 diabetes: a systematic review and meta-analysis

Aims: To provide a systematic review and meta-analysis of recent evidence on the effectiveness of lifestyle-based weight loss interventions for adults with type 2 diabetes. Methods: A search of the literature from January 2003 to July 2013 was conducted (PubMed, Embase, CINAHL and Web of Science). The studies considered eligible were randomized controlled trials evaluating weight loss interventions (diet and physical activity, with or without behavioural strategies) of >= 12 weeks duration, compared with usual care or another comparison intervention. Ten studies were included for review. Some heterogeneity was present in the sample, therefore, random-effects models were used to calculate pooled effects. Results: Intervention duration ranged from 16 weeks to 9 years, with all but one delivered via individual or group face-to-face sessions. From six studies comparing lifestyle intervention with usual care the pooled effect on weight (n=5795) was -3.33 kg [95% confidence interval (CI) -5.06, -1.60 kg], and on glycated haemoglobin (HbA1c; n=5784) was -0.29% (95% CI -0.61, 0.03%), with both attenuated in sensitivity analyses. The pooled within-group effect on weight (n=3063) from all 10 lifestyle intervention groups was -5.33 kg (95% CI -7.33, -3.34 kg), also attenuated in sensitivity analyses. None of the participant or intervention characteristics examined explained the heterogeneity. Only one study assessed whether intervention effects were maintained after the end of the intervention. Conclusions: Lifestyle-based weight loss intervention trials in type 2 diabetes achieve, on average, modest reductions in weight and HbA1c levels, but results were heavily influenced by one trial. Evidence-based approaches for improving the effectiveness of lifestyle-based interventions in type 2 diabetes are needed, along with future studies reporting on maintenance and cost-effectiveness.