Meta-Analysis of Anthropometric Outcomes of Motivational Physical Activity Interventions

1. Meta-Analysis of Anthropometric Outcomes of Motivational Physical Activity Interventions Jo-Ana D. Chase MN APN-BC Todd Ruppar PhD RN GCNS-BC Lorraine J. Phillips PhD RN Vicki S. Conn PhD RN FAAN University of Missouri Sinclair School of Nursing

2. Acknowledgements • Parent study and funding: Meta-analysis of interventions to increase exercise/physical activity (R01NR009656, Dr. Vicki Conn – Principal Investigator)

3. Background • Prevalence of obesity increasing • Obesity linked with multiple chronic illnesses (Guh, et al, 2009; Suzuki, Orsini, Safi, Key, & Wolk, 2009) • Inadequate physical activity (PA) contributes to epidemic of obesity (Rossner, et al., 2008; Wareham, van Slujs, & Ekelund, 2005) • Many interventions designed to motivate subjects to increase PA have also examined anthropometric outcomes

4. Background • Prior meta-analyses of PA anthropometric outcomes • Limited with no moderator analysis • No separation of outcomes for diet or PA interventions • Most comprehensive meta-analysis of PA on anthropometric outcomes – Ballor and Keesey, 1991

5. Research Questions • What is the overall effect of interventions designed to motivate subjects to increase PA on anthropometric outcomes? • Do anthropometric effects of these interventions vary depending on intervention, sample, or design attributes?

6. Methods • Comprehensive search  motivational PA intervention studies reporting anthropometric outcomes (e.g., BMI, percent body fat, central obesity) in healthy adult subjects • “Motivational PA intervention” = any deliberate intervention intended to motivate subjects to increase PA behavior, excluding supervised exercise sessions

7. Methods – Data Extraction • Coding frame developed from prior, related research and pilot tested • Study characteristics (e.g., published/unpublished, funding) • Sample characteristics (e.g., age, gender) • Intervention characteristics (e.g., dose, delivery) • Effect size information

8. Methods – Data Extraction • Studies coded by two independent and extensively trained coders • Coders compared all variables to reach consensus • All effect size data independently verified by doctorally prepared researcher

9. Methods - Analysis • Standardized mean difference effect sizes (ES, d) under random-effects model • Studies weighted by inverse of the variance • Heterogeneity examined: Q statistic and I2 • Exploratory moderator analyses – meta-analytic analogues of ANOVA (dichotomous moderators) and regression (continuous moderators) d = meantreatment - meancontrol Pooled standard deviation

10. Study Characteristics • Reviewed 54,642 potentially eligible reports • ES calculated from data for 94,711 subjects • Two group comparisons: • 76 comparisons • 94,711 subjects • Single group, treatment pre-post comparisons • 436 comparisons • 56,258 subjects

11. Sample Characteristics • Sample sizes • Two group: median 56 subjects • Single group: median 52 subjects • Percent female: median 81% • Percent minority: median 15% • Baseline BMI: median 27-30 kg/m2

12. Intervention Characteristics • Number of intervention strategies: median 3 • Total number of intervention minutes: median 720 minutes • Recommended minutes of PA per session: median 30 minutes • Recommended minutes of PA per week: median 140 minutes

13. Results – Anthropometric Outcomes k=number of comparisons ES=effect size p=test of statistical significance for effect size I2=index of heterogeneity beyond within-study sampling error

14. Effect Size Meanings • Converted ES to original metrics – weight (kg) and BMI • Mean difference of 1.3 kg between treatment and control subjects at outcome • BMI difference of 0.4 between treatment and control subjects at outcome (ex. 27 vs. 27.4)

15. Results – Moderator Analyses • Larger ESs for interventions using transtheoretical model (TTM) (d=0.21) vs. social cognitive theory (SCT) (d=0.07) • Studies with mean ages in 30s and early 60s demonstrated higher ESs than studies with other age groups • Studies recommending walking were not more effective in improving anthropometric outcomes than studies recommending other forms of exercise

16. Limitations • Study specific • Anthropometric measurement error • Low reporting of ethnic diversity among samples • Long-term results not often examined • Study quality and treatment fidelity • Meta-analysis specific • Exclusion of studies based on insufficient information • Findings observational • Moderator analyses – hypothesis generating

17. Discussion • Findings support significant improvements in anthropometric outcomes associated with motivational PA interventions • Future research to directly compare TTM-based to SCT-based interventions • Future research to test interventions recommending varied forms of PA (not just walking)

18. References • Ballor, D. L., & Keesey, R. E. (1991). A meta-analysis of the factors affecting exercise-induced changes in body mass, fat mass and fat-free mass in males and females. International Journal of Obesity, 15(11), 717-726. • Guh, D. P., Zhang, W., Bansback, N., Amarsi, Z., Birmingham, C. L., & Anis, A. H. (2009). The incidence of co-morbidities related to obesity and overweight: a systematic review and meta-analysis. BMC Public Health, 9, 88. • Rossner, S., Hammarstrand, M., Hemmingsson, E., Neovius, M., & Johansson, K. (2008). Long-term weight loss and weight-loss maintenance strategies. Obesity Reviews, 9(6), 624-630. • Suzuki, R., Orsini, N., Saji, S., Key, T. J., & Wolk, A. (2009). Body weight and incidence of breast cancer defined by estrogen and progesterone receptor status--a meta-analysis. International Journal of Cancer, 124(3), 698-712. • Wareham, N. J., van Sluijs, E. M. F., & Ekelund, U. (2005). Physical activity and obesity prevention: a review of the current evidence.[erratum appears in Proc Nutr Soc. 2005 Nov;64(4):581-4]. Proceedings of the Nutrition Society, 64(2), 229-247.