This review found that internet-based components in obesity treatment programmes conferred small additional benefits on weight control compared to programmes with no internet-based components. The reliability of the authors' cautious conclusions is unclear because of the variability in results across the included studies.

To evaluate the impact of an internet component in obesity treatment programmes for weight loss or weight management.

MEDLINE and EMBASE were searched from 1980 to April 2011; search terms were reported. Reference lists from retrieved publications were checked for additional references. There were no language restrictions.

Parallel randomised controlled trials of overweight or obese adults in which weight loss or management interventions with an internet-based component were compared to interventions without internet-based components were eligible for inclusion. Both groups had to receive interventions that included control of dietary intake and increasing physical activity. Effects of the interventions were assessed by absolute body weight change. Internet-based components of the interventions were to have roles as supplemental or substitute tools. Interventions were considered to be internet-based if the individualised instruction, support for self-monitored physical activity and dietary intake or counselling with intervention providers were provided via the Internet.

The included trials were conducted in USA, Japan, The Netherlands, UK and Korea. Mean age of the patients ranged from 33.1 to 58.2 years. Mean body mass index ranged from 26.2kg/m^-2 to 35.7kg/m^-2. Internet interventions consisted of individualised instructions, provision of content in addition to instructions, provision of reporting of diet and physical activity information facilities and communication via email with lifestyle instructors. Treatment in the control groups consisted of in-person counselling, frequent support, initial counselling, self-hep, and face-to-face-contact and group meetings.

Three reviewers performed study selection. Any discrepancies were resolved by a fourth reviewer.

The authors did not assess methodological quality formally but considered descriptions of randomisation and compliance and whether intention-to treat analyses were used.

The authors did not state how many reviewers extracted these data.

Data were extracted to calculate effect sizes and corresponding 95% confidence intervals (CI) for weight change outcomes. Standard errors for weight change were extracted from the studies or estimated from p-values or standard errors of the baseline and final weights.

The authors did not state how many reviewers extracted data.

Pooled effect sizes and 95% CIs were calculated using a fixed-effect model. Statistical heterogeneity was evaluated using Ι². Where statistical heterogeneity was significant the effect sizes were pooled using a random-effects model. The reviewers assessed publication bias with Egger's and Begg's tests and visual appraisals of funnel plots. Subgroup analyses were conducted on the basis of key study characteristics such as goals of treatment, length of educational periods as the use of the intervention as a substitute for face-to-face support.

Twenty-five trials (8,697 participants) were included in the review. Interventions ranged from three to 30 months; only eight trials had intervention periods of 12 months or more. Drop-out rates ranged from zero to 79.6% (mean drop-out rate of 17.6% and reasons for drop-outs were reported in 12 studies. Randomisation methods were described in seven studies. Compliance was not reported in 11 trials. Intention-to-treat analyses were conducted in 17 trials.

Internet use was associated with a statistically significant additional effect on weight loss compared to patients in non-internet-user control groups (weight change -0.68kg, 95% CI -1.29 to -0.08) although statistically significant heterogeneity was observed across the trials (Ι²=84.4%).

The results of subgroup analyses indicated that adverse effects on weight loss were observed when the internet was used as a substitute for face-to-face support (weight change 1.27kg, 95% CI 0.29 to 2.25; Ι²=73.7; eight trials). Internet-based programmes were effective when the goal of treatment was initial weight loss (weight change -1.01kg, 95% CI -1.68 to -0.34; Ι²=85.2%; 20 trials) but there were no differences between groups when the goal of treatment was weight maintenance (weight change 0.68kg, 95% CI -0.50 to 0.85; Ι²=61.9%; five trials).

Statistically significant advantages of the internet-based interventions were observed when face-to-face support was provided (weight change -1.93kg, 95% CI -2.71 to -1.15; Ι²=67.9%; nine trials) when individualised instructions were provided via the Internet (weight change -1.33kg, 95% CI -2.32 to -0.34; Ι²=85.2%; nine trials) and when educational periods were six months duration or less (weight change -1.55kg, 95% CI -2.05 to -1.05; Ι²=10.6%; nine trials).

There was no evidence of publication bias identified by visual appraisals of the funnel plots or by Egger's and Begg's tests.

Internet components in obesity treatment programmes were associated with modest but significant effects of weight control compared to interventions that did not involve use of the Internet.

Two appropriate databases were searched for relevant studies which means the search was limited. There were no attempts to identify unpublished studies which risks of publication bias. Steps were taken to minimise reviewer error and bias for the selection of studies, but were not reported for data extraction. Some aspects of methodological quality were assessed and from this assessment the trials appeared to be of medium to poor quality; drop-out rates of more than 10% were reported in most trials. Substantial heterogeneity was observed for almost all the results (including subgroup analyses) so the justification for the authors' decision to combine the results was unclear. The authors correctly acknowledged the small size of the observed effects of the interventions and limitations of short follow-up in most of the trials.

Methodological limitations of potential publication bias and the combination of heterogeneous studies in a meta-analysis make the reliability of the authors' cautious conclusions unclear.

Practice: The authors stated that internet-based lifestyle modifications should gradually become more intensive or should be combined with in-person support, particularly when the aim was to maintain long term weight loss.

Research: The authors stated a need for further research on issues such as examination of cost-benefit ratios and to determine optimal proportions of online and in-person obesity care support and characteristics of obesity care that may benefit from supplemental care using the Internet.

Japan Cardiovascular Research Foundation; Ministry of Health, Labour and Welfare; Japan Society for the Promotion of Science.

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.