Associations between parenting partners' objectively-assessed physical activity and Body Mass Index: A cross-sectional study

•Accelerometer derived levels of MVPA in parents are associated.•Every 9 min of father MVPA predicts a 3 minute increase for mothers.•Self-reported BMI scores of mothers and fathers are associated.•Parents accumulated approximately 10 min less MVPA at the weekend.•Behaviour change in one parent may have a knock on effect for a spouse.

ObjectiveFamily members have the capacity to influence each other's health behaviours. This study examined whether there were associations in the objectively assessed physical activity and Body Mass Index (BMI) of mothers and fathers.MethodsRecruitment took place in Bristol (UK) during 2012/13. Participants were 272 pairs of parents (dyads) that wore an accelerometer for at least 500 min on 3 or more days. Parents provided demographic information and self-reported height and weight. Multi-variable linear and logistic regression models examined the relationships between parents' moderate-to-vigorous physical activity (MVPA) and BMI.ResultsMVPA minutes (r = 0.26, p < 0.001) and Body Mass Index (r = 0.20, p = 0.002) of parents were correlated. Logistic regression analysis showed that mothers were almost twice (OR 1.87, p < 0.05) as likely to be overweight or obese when fathers were. Linear regression models showed that at the weekend every 9 min of paternal MVPA was associated with 3 min of maternal MVPA (r = 0.34, p < 0.001).ConclusionsBoth physical activity and BMI of parenting partners were associated. Since parents tend to share home environments and often perform activities together or as a family, then behavioural changes in one parent may have a ripple effect for other family members.