This well-conducted review found that there was no high quality evidence to suggest that lifestyle modifications had an effect on short-term or long-term glycaemic control in children and adolescents with type 2 diabetes mellitus. The results from one small poor-quality study means that it is difficult to make a judgement about the reliability of the authors' conclusions.

To evaluate the impact of lifestyle modification interventions on glycaemic control in children and adolescents with type 2 diabetes mellitus.

MEDLINE, EMBASE, CINAHL, the Cochrane Library, PASCAL, PsycINFO and Sociological Abstracts were searched from inception to October 2007 and updated in May 2009; search terms were reported. References from all retrieved articles and review articles published since January 2002 were checked to identify additional references. Experts were contacted to identify additional unpublished studies. There were no language restrictions.

Comparative studies designed to evaluate the effect of lifestyle modification by diet and/or physical activity on glycaemic control in patients under 18 years of age with type 2 diabetes mellitus were eligible for inclusion. Studies on lifestyle modification and glycaemic control (glycated haemoglobin levels) in children or youth with impaired glucose tolerance or impaired fasting glucose were excluded from the review.

The included study evaluated the use of a ketogenic very low carbohydrate diet in the treatment of type 2 diabetes; it was a retrospective case control study of morbidly obese (body mass index over 30kg/m²) youth (14.5 ± 0.4 years old). The study was conducted at a hospital-based outpatient paediatric diabetes clinic. The control group were patients with type 2 diabetes matched by age, race, gender, body mass index, diabetes duration, glycated haemoglobin levels and pharmacotherapy use.

Two reviewers independently performed the study selection. On completion of the initial review, a third reviewer resolved any discrepancies by consensus.

Two reviewers independently assessed methodological quality using criteria from Downs and Black. Several study characteristics were assessed on internal and external validity, power and reporting. A quality score of more than 20 indicated a high quality study; scores between 11 and 20 were rated as moderate; studies allocated a score of below 11 were rated as poor. Any disagreements between the reviewers were resolved by discussion with a third reviewer.

The reviewers did not state how they would have summarised the results if multiple studies were selected for review. The results of the included study were summarised in a narrative review supported by a table.

One retrospective case control study (n=35 participants) was included in the review. The quality score allocated to the study was 8 points, which indicated a poor quality study.

At eigth weeks, participants who adhered to the very low carbohydrate diet (for more than six weeks) had reductions in glycated haemoglobin levels of 16% (8.8 ± 0.6 to 7.4 ± 0.6; p<0.005) and body mass index (43.5 ± 1.8kg/m² to 39.3 ± 1.7kg/m²; p<0.0001).

At two years follow-up, glycaemic control had returned to baseline levels for the very low carbohydrate diet group. There was a sustained improvement in body mass index in the very low carbohydrate diet group at two years follow-up (p<0.05) compared with the control group (who had a 3.7% increase in baseline).

There was no high quality evidence to suggest that lifestyle modifications had an effect on short-term or long-term glycaemic control in children and youth with type 2 diabetes mellitus. More research is required to define optimal lifestyle behaviour strategies.

The review addressed a clear question. Criteria for the inclusion of studies were stipulated. Appropriate databases were searched with no language restrictions. Attempts were made to identify unpublished studies. The reviewers reported steps to minimise errors and bias for study selection, the assessment of methodological quality and data extraction.

Little information was reported about the patients and the intervention in the only included study. It was difficult to determine baseline values of glycosylated haemoglobin. The authors acknowledged some of the limitations of the review, particularly the paucity of well-designed studies in this area.

Although the review was well conducted, the reliance on one poor quality study means that it is difficult to make a judgement about the reliability and generalisability of the authors' conclusions.

Practice: The authors did not state any implications for practice.

Research: The authors stated that randomised clinical trials are required to clearly determine the role of nutrition and physical activity interventions in managing paediatric type 2 diabetes mellitus. Studies such as these that consider quantitative and qualitative elements of nutrition and physical activity may also determine optimal lifestyle treatment approaches for good glycaemic control independent of pharmacological therapy for the paediatric populations with type 2 diabetes.

Alberta Innovates - Health Solutions, Population Health Investigator Award; Canadian Insitutes of Health Research (CIHR) awards; Canadian Child Health Clinician Scientist Program; Swedish Heart-Lung Foundation (20070633); Swedish Diabetes Foundation (DIA 2006-013); Vasterbotten's Health Authority, Sweden (ALF strategic appointment 2006-2009).

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.