A systematic review and meta-analysis of weight loss in control group participants of lifestyle randomized trials and weight management.
The aim of this study was to assess weight loss in control group participants of lifestyle randomized trials and weight management. We searched PubMed, MEDLINE, Embase, and the Cochrane Library from inception to December 31, 2016, for studies that randomized adults to a lifestyle or weight management intervention or control group and reported mean change in weight from baseline to end of follow-up in the control group. Two reviewers independently extracted data on study design, participant characteristics, and weight loss outcomes. Weight loss was calculated as the difference between the mean weight at baseline and end of follow-up for the control group. A random-effects model was used to calculate the pooled mean weight loss. Heterogeneity was assessed using the I2 statistic.
A total of 29 studies (n = 3,614 control group participants) met the inclusion criteria. The pooled mean weight loss was −0.35 kg (95% confidence interval [CI], −0.57 to −0.12 kg; I2 = 56%) at 3 months, −0.37 kg (95% CI, −0.61 to −0.13 kg; I2 = 53%) at 6 months, and −0.41 kg (95% CI, −0.68 to −0.15 kg; I2 = 57%) at 12 months. There was no evidence of publication bias.
In conclusion, control group participants in lifestyle and weight management trials lost a small amount of weight over the course of the trial. These results suggest that the benefits of lifestyle and weight management interventions on weight may be partly due to the Hawthorne effect.
A systematic review and meta-analysis of weight loss in control group participants of lifestyle randomized trials
Background: The long-term effects of lifestyle interventions on weight loss are debated.
Objective: To determine the effect of lifestyle interventions on weight loss in control group participants of randomized trials with a minimum follow-up of 1 year.
Methods: MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were searched from inception to January 2017 for randomized trials comparing lifestyle interventions with control conditions. Study selection, data abstraction, and quality assessment were performed in duplicate. A random-effects model was used to pool weighted mean differences (WMDs) in intention-to-treat weight loss at 1-year follow-up.
Results: Of 15,120 identified citations, 44 unique trials with 5943 control group participants were eligible. The control group participants lost a mean (SD) of 1.22 (2.52) kg at 1-year follow-up (WMD, − 0.15 kg; 95% CI, − 0.29 to − 0.01 kg). The pooled estimate was not significantly different from zero in sensitivity analyses restricted to trials with a low risk of bias or that used an active control group.
Conclusion: Lifestyle interventions resulted in small, nonsignificant weight loss in control group participants. These data suggest that the weight-loss effects of lifestyle interventions may be explained by factors other than the interventions themselves.
Clinical trials that compare lifestyle interventions with control conditions provide an opportunity to study the long-term effects of these interventions on weight loss. The control group participants in these trials are not asked to make any changes to their lifestyle and act as a “treatment” comparison for those in the intervention group.
A systematic review and meta-analysis of weight loss in control group participants of lifestyle randomized trials was conducted to determine the effect of lifestyle interventions on weight loss. The control group participants lost a mean (SD) of 1.22 (2.52) kg at 1-year follow-up (WMD, − 0.15 kg; 95% CI, − 0.29 to − 0.01 kg). The pooled estimate was not significantly different from zero in sensitivity analyses restricted to trials with a low risk of bias or that used an active control group.
These data suggest that the weight-loss effects of lifestyle interventions may be explained by factors other than the interventions themselves.
