The Impact of Social Media Interventions on Weight Reduction and Physical Activity Improvement Among Healthy Adults: Systematic Review

**Background:** Sedentary lifestyle and overweight/obesity are well-established cardiovascular risk factors contributing substantially to the global burden of disease. Regular physical activity (at least 150 minutes of moderate intensity or 75 minutes of vigorous physical activity per week) and weight management (BMI 18.5-24.9 kg/m²) are recommended for cardiovascular risk reduction. Worldwide, one-quarter of adults are inactive, and approximately 52% of adults are affected by overweight or obesity. Social media interventions show promise in supporting health behavior change, but previous reviews reported contradictory evidence regarding their efficacy and the relationship between engagement and outcomes.

**Methods:** This systematic review followed PRISMA guidelines and was registered in PROSPERO (CRD42022311430). CINAHL and MEDLINE were searched for randomized trials published between 2011 and 2021 in English. Studies were included if they used social media tools providing explicit interactions between participants to enhance physical activity or weight reduction in healthy adults (no documented chronic conditions). Studies were excluded if the intervention was passively delivered through an app/website or if participants had known chronic disease. One reviewer screened titles and abstracts; two reviewers assessed full texts. Three reviewers independently assessed quality using the revised Cochrane risk-of-bias tool (ROB2). Narrative synthesis was used due to heterogeneity of included studies.

**Key Results:** Seventeen papers reporting 16 studies from 4 countries with 7372 participants were included. Of these, 56% (9/16) explored effects on physical activity, 38% (6/16) investigated weight reduction, and 6% (1/16) assessed both. Intervention duration ranged from 2 to 24 months. Facebook was the primary modality in one study and part of multicomponent interventions in 38% (6/16) of studies.

FOR PHYSICAL ACTIVITY

70% (7/10) of studies reported significant improvement between groups, while 30% (3/10) found no significant improvement. Among studies finding no significant between-group differences, 67% (2/3) reported significant within-group improvements over time. Three studies assessed predictors and found significant correlation between baseline physical activity and changes (P<.001 to P=.04).

FOR WEIGHT LOSS

57% (4/7) of studies reported significant between-group differences favoring social media interventions. Balk-Møller et al reported mean weight difference of −2.36 kg (−3.23 to −1.49; P<.01) at 16 weeks and −1.64 kg (−3.04 to −0.24; P<.05) at 38 weeks in the weight loss subgroup. Godino et al found mean weight difference of −1.33 kg at 6 and 12 months (P<.05), but no significant difference at 18 and 24 months. Two studies (29%) found no significant between-group differences.

Engagement was reported in 69% (11/16) of studies with no standard metrics. A decline in engagement was reported in 44% (7/16) of studies. Engagement was not a predictor of behavior change in 45% (5/11) of studies but was related to behavior change in 55% (6/11) of studies.

**Clinical Implications:** The evidence for social media interventions to improve physical activity and weight loss in healthy adults is mixed, with some short-term benefits but no demonstrated long-term effectiveness. The multifaceted nature of interventions makes it difficult to identify which components drive efficacy. No included studies involved healthcare professionals, representing a gap in the literature. The inconsistent relationship between engagement and outcomes, coupled with declining engagement over time and lack of standardized engagement metrics, limits the ability to make evidence-based recommendations. Future research should focus on identifying effective intervention components, optimal intervention dose, standardizing engagement measurement, and integrating social media interventions with existing healthcare services rather than creating separate preventive care avenues.