The review included 17 randomised controlled trials (810 participants).
Non-pharmacological interventions resulted in a significant weight change of -3.12kg (95% CI -4.03 to -2.21; 14 studies, no significant heterogeneity) and a significant change of BMI of -0.94kg/m² (95% CI -1.45 to -0.43; 16 studies, significant heterogeneity) compared to control. In both cases, changes were similar for prevention and treatment trials. Where reported, there were also significant reductions in waist circumference, percentage body fat and proportion of participants who gained 7% or more of weight.
Where reported, the intervention groups also showed significant reductions in insulin levels, fasting glucose, total cholesterol, low density lipoprotein cholesterol and triglycerides compared to control. There were no significant differences seen in high density lipoprotein cholesterol, systolic blood pressure and all-cause discontinuation rates.
There was substantial heterogeneity in many of the analyses.
Subgroup analyses: The authors reported a larger effect on weight and BMI for outpatient populations than for in-patient or mixed populations and also for nutrition and/or exercise interventions than for cognitive-behavioural interventions but did not report whether differences were statistically significant. No significant differences were seen for the other subgroup analyses carried out. Results for maintenance of weight or BMI loss after the end of the interventions were mixed (significant for studies that reported weight loss but not for studies that reported BMI after an average of 3.6 months' follow-up).
The authors found no evidence of small study bias (funnel plot evaluation).