Does Motivational Interviewing Improve the Weight Management Process in Adolescents? A Systematic Review and Meta-analysis

Background: Due to the complex nature and high heterogeneity of motivational interviewing (MI) trials, available data on the effectiveness of these interventions on weight management in the early years of life is not yet conclusive. This study aimed to (1) evaluate the effectiveness of MI-based interventions on modifying obesity-related behaviors and consequently controlling weight in adolescents, and (2) determine characteristics of participants and interventions through sub-group analysis. Methods: Electronic databases, i.e., Medline, Elsevier, ISI, Cochrane Central Register of Controlled Trials (Clinical Trials), PsycINFO, and subject-related key journals were searched for randomized controlled trials that investigated the effect of MI-based interventions on weight management in overweight/obese adolescents. Primary outcomes were BMI, BMI Z-score, waist circumference, and fat percentage. Secondary outcomes were related behaviors (dietary intake and physical activity) and cognitive abilities (self-efficacy, self-regulation, self-control). Of the 3673 studies initially screened for eligibility, nineteen studies met the inclusion criteria and eighteen studies were entered in the meta-analysis. Meta-regression and sub-group analyses were conducted to control the high heterogeneity of studies. Sensitivity analysis has been conducted based on the Cochrane guidelines using the leave-one-out methods. Results: MI-based interventions did not affect on all primary outcomes, including BMI, BMI Z-score, waist circumference, and fat percentage; however, in terms of secondary outcomes, only sugary beverage intake was reduced in adolescents (SMD = − 0.47, K = 3, I² = 26.2%). Physical activity and cognitive variables were not considered in the current analysis due to limited data and high heterogeneity in measurements and reports. In addition, findings of sensitivity results showed that MI could significantly reduce waist circumference among adolescents (SMD = − 0.51, 95% CI − 0.91 to − 0.11). In terms of subgroup analysis, our results showed that various characteristics of participants (age, sex, weight status) and interventions (parental involvement, study duration, fidelity assessment, type of the control groups) could affect related primary and secondary outcomes among adolescents. Conclusion: MI-based behavioral interventions had minor effects on reducing sugary beverage intake in all adolescents while a reduction in central obesity was noted predominantly among girls and those with complete participation. The current results indicate that the main characteristics influencing goal achievement in MI interventions are the age of participants, MI fidelity assessment, parental involvement, duration of interventions, and type of the control groups.