Meta-analysis of Anthropometric Outcomes of Supervised Exercise Interventions in Healthy Adults

1. Meta-analysis of Anthropometric Outcomes of Supervised Exercise Interventions in Healthy Adults Vicki Conn PhD RN FAAN Todd Ruppar PhD RN Lorraine Phillips PhD RN Jo-Ana Chase MSN RN Meta-Analysis Research Center University of Missouri School of Nursing

2. Parent Study: Meta-Analysis of Physical Activity Interventions in Healthy People Funding: Meta-analysis of interventions to increase exercise & physical activity (R01NR07870) Vicki Conn, principal investigator Grant co-investigators: Adam Hafdahl PhD David Mehr MD MS Diane Johnson MS

3. Extant Research Evidence mixed about effects of PA on anthropometric outcomes Limited previous meta-analyses: Focused on clinical populations Did not report findings separately for exercise and diet changes Did not separate supervised exercise and motivational interventions 1991 last semi-comprehensive meta-analysis No previous moderator analyses

4. Research Questions What is the overall effect of supervised exercise interventions on anthropometric outcomes? How do the anthropometric effects of supervised exercise vary depending on sample, design, or intervention characteristics?

5. ‘Healthy’ adult sample • Samples included regardless of anthropometric status at entry • Supervised exercise with verified exercise dose • Adequate data to calculate effect size for body mass index (BMI), weight, percent body fat, or central obesity (abdominal girth, waist-to-hip ratio) Inclusion Criteria

6. Searched 14 computerized databases • MEDLINE & PsycINFO • EMBASE • Cochrane Controlled Trials Register • Database of Abstracts of Reviews of Effectiveness • Healthstar • Combined Health Information Database • Educational Resources Information Center • Sport Discus • Dissertation Abstracts International Search Strategies (1)

7. Ancestry searches • Author searches from all primary studies • Hand searches of 114 journals • Conference abstracts (e.g. ACSM, APHA, AHA, MNRS, SBM) • Research registers (e.g. CRISP [RePORT]) • Reviewed 54,642 studies for potential eligibility Search Strategies (2)

8. Source characteristics • Published vs. unpublished • Year of distribution • Participant attributes • Ages • Gender/minority distribution • Methodological features • Supervised exercise intervention characteristics • Effect size information Coding Data Categories

9. Basic conceptual definition of standardized mean difference (d): • X1 – X2 d = SD1 + SD2 2 • Meta-analysis equations convert to d index from: • Change scores • Comparison of unadjusted means by t statistic • Two group F statistic • P values for t statistic • Proportions (success rates) • Correlations Calculating Effect Sizes

10. Random effect model • Assumes heterogeneity beyond sampling error • Appropriate with variations in research methods (interventions, measures, samples) • Effect sizes weighted by inverse of variance • Effect sizes adjusted for bias • Q & I2 statistics to examine heterogeneity • Moderator analyses: • Dichotomous: meta-analysis analogue of ANOVA • Continuous: meta-analysis analog of regression Analyses

11. Study Characteristics • Two-group comparisons: treatment vs. control • 316 comparisons • 24,689 people • Single-group comparisons: treatment baseline vs. treatment outcome • 794 comparisons • 20,335 people

12. Sample Characteristics • Sample sizes: • Two group: median 23 subjects • Single group: median 17 subjects • Modest attrition: median 7% • Age: median 38 years • Percent female: median 55% • Percent minority: median 13% (poorly reported) • Baseline BMI: median 27 – 28 kg/m2

13. Typical Intervention Characteristics Supervised exercise interventions: • 47 minutes per session • 3 sessions per week • 42 total sessions

14. Anthropometric Outcomes k = number of comparisons ES = effect size (d index) p = test of statistical significance of effect size I2 = index of heterogeneity beyond within-study sampling error

15. Effect Size Meaning • Converted effect size (treatment vs. control at outcome) to original metric of BMI • Effect size * BMI SD = difference in original metric (.21 * 4.6 =.97) • At outcome: • Treatment subjects BMI = 27.0 • Control subjects BMI = 28.0 • Mean difference 2.3 kg between treatment and control subjects

16. Significant Moderators • Previous exercise: studies of people with existing exercise behavior reported lower ES (.11) than studies of sedentary subjects (ES = .24) • Lower effect size for studies with more minority subjects (B = -.26) • Larger exercise dose associated with better anthropometric outcomes: • Studies with more total number of exercise sessions reported larger effect sizes (B = .29): remained important in multivariate analyses • Studies with more total minutes of supervised exercise reported larger effect sizes (B = .29): total number of exercise sessions more important

17. Potential Moderators Which Were Not Significant • Publication year • Published vs. unpublished report • Presence of funding • Sample characteristics: gender, age, BMI • Random vs. non-random assignment • Behavioral target (exclusively PA vs. PA plus diet) • Fitness testing present vs. absent • Aerobic exercise only vs. aerobic plus resistance • Individual components of exercise dose: • Minutes of exercise per session • Frequency of sessions per week

18. Limitations • Primary studies often poorly report interventions, minority participants, and statistical outcomes • Anthropometric outcomes may have measurement error • Need research with documented exercise dose over years to determine health outcomes • Future meta-analyses focus on overweight/obese adults

19. Discussion • Clinically important improvement in BMI following interventions (BMI = 28 vs. 27; Kg = 2.3 difference) • Important health benefit across years of exercise • Exercise may be more effective in preventing gain • Exercise confers benefits beyond anthropometric outcomes • Minority subjects may experience less improvement • Dose matters: total number of sessions most important (but few studies with brief or infrequent sessions)