The Beneficial Effects of Physical Activity: Is It Down to Your Genes? A Systematic Review and Meta-Analysis of Twin and Family Studies

BACKGROUND: There is evidence for considerable heterogeneity in the responsiveness to regular physical activity (PA) which might reflect the influence of genetic factors. The aim of this systematic review was to assess whether the response to a PA intervention for measures of body composition and cardiorespiratory fitness is (i) correlated within twin pairs and/or families and (ii) more correlated in monozygotic twins (MZ) compared to dizygotic twins (DZ), which would be consistent with genetic effects. METHODS: were extracted from included studies, although heritability estimates were not reported as small sample sizes made them uninformative. RESULTS: = 0.39, n = 48), where "n" represents the total number of twin pairs from all studies. Maximal heritability estimates ranged from 0-21% for measures of body composition, and 22-57% for cardiorespiratory fitness. Twin studies differed in sample age, baseline values, and PA intervention, although the exclusion of any one study did not affect the results. CONCLUSIONS: Shared familial factors, including genetics, are likely to be a significant contributor to the response of body composition and cardiorespiratory fitness following PA. Genetic factors may explain individual variation in the response to PA. TRIAL REGISTRATIONS: PROSPERO Registration No CRD42015020056 .