Even control participants see weight loss benefit in lifestyle trials

In trials that test lifestyle modification interventions, even participants randomized to control groups see significant weight loss, reports a recent meta-analysis.

Drawing from the online databases of Medline, Scopus, Web of Science, Clinicaltrials.gov, and Cochrane library, the researchers retrieved 22 studies involving a total of 4,032 participants. Weight loss was assessed in the control group by comparing participants’ pre- and postintervention weights, using a random effects model to evaluate the statistical significance of average values.

Overall, control participants lost a statistically significant mean of 0.41 kg (95 percent confidence interval [CI], –0.53 to –0.28; p<0.001).

Duration of trial follow-ups appeared to be an important determinant in such an effect. The mean weight loss was 0.51 kg (95 percent CI, –0.68 to –0.3) in control participants at 1–4 months of follow-up. This decreased to 0.32 kg (95 percent CI, –0.58 to –0.07) at 5–12 months.

When follow-up extended beyond 12 months, average weight loss was 0.20 kg, which was not statistically significant anymore (95 percent CI, –0.49 to 0.10).

The overall effect remained true in studies whose control groups were given combined standard care, expert advice, and educational materials (mean difference, –0.65 kg, 95 percent CI, –1.03 to –0.27).

Weight loss did not significantly differ between control and treatment groups when waitlists were included as controls (mean difference, –0.84 kg, 95 percent CI, –2.47 to 0.80) or when analysis was focused on high-quality studies (mean difference, –0.16 kg, 95 percent CI, –0.39 to 0.09).

“Our systematic review showed that participation in control groups of RCTs of lifestyle interventions had a benefit in terms of weight loss in meta-analysis with heterogeneity,” the researchers said. “That control groups accrue benefits should be included in patient information sheets to encourage participation in future trials among patients with overweight or obesity.”