Background: Partnering and parenting are important life-stage transitions that may associate with changes in weight, domain-specific physical activity (PA) and sedentary behaviours in young adults.
Methods: 2,124 Australian adults (mean age 31.7 (2.7) years, 47.5% male) completed questionnaires in 2004-06 and 2009-11 and reported marital and parental status, and weight (kg). Physical activity (PA) and sedentary behaviours were measured in a subset (n=1,217) using the International PA Questionnaire. Linear regression estimated the associations of life-stage transitions (those remaining not partnered or childfree were reference groups) with the change in weight, PA or sedentary behaviour during follow-up, adjusted for baseline weight/PA/sedentary behaviour, age, education, follow-up duration and other life-stage transition.
Results: During the 5-year follow-up, 17.3% men and 12.9% women became partnered, and 27.3% men and 19.1% women had their first child. Becoming partnered had little effect on weight, total PA and sedentary behaviours although women who partnered gained weight (β 2.2kg, 95% Confidence Interval (CI) 0.6 to 3.7). For women only, separation/divorce/widowhood was associated with less sitting time (β 49.5mins/day, 95% CI 1.7 to 97.2) than remaining partnered.
Compared to remaining childfree, having a first child during follow-up was associated with significant reductions in total PA (β -119.9mins/week, 95% CI -227.9 to -12.0) and TV viewing time (β -26.4mins/day, 95% CI -46.5 to -6.2) in men. Women having a first child gained weight (β 1.6kg, 95% CI 0.4 to 2.9) and spent less time sitting (β -108.5mins/day, 95% CI -139.4 to -77.7). For women only, having additional children was associated with less sitting time (β -42.2mins/week, 95% CI -68.6 to -15.9) than having the same number of children.
Conclusions: Women appear to be more susceptible than men to weight and sedentary behaviour changes following partnering transition. Parenting transition was associated with both health-promoting and health-damaging changes in men and women.