Transition to parenthood: Changes in body weight, body composition and energy balance related behavior

Research output: ThesisPhD Thesis

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Becoming a parent represents a lifechanging period for women and men. Both parents are at risk to change their body weight, body composition and energy balance related behavior (EBRB), i.e., diet, physical activity (PA) and sedentary behavior (SB) during the pregnancy and the postpartum period. Understanding this critical period and the changes parents(-to-be) experience can facilitate the development of health promotion programs. Although the transition to parenthood is often associated with pregnancy-related weight gain and retention in women, evidence on the effect of having a first child on men’s body weight is lacking. Data on (changes in) men’s weight and EBRB prior to and following the birth of a child are needed in order to provide a more comprehensive understanding of the impact of fatherhood on men’s lifestyle and health. It is also unclear whether pregnancy-related weight gain and retention cohere with unfavorable changes in body composition and EBRB in both women and men transitioning to parenthood, considering a couple-perspective. Using a mixed-methods design, the overall aim of the present doctoral thesis was to provide insight into this critical transition phase. To this end, an observational follow-up study was used to investigate changes in body weight, body composition and EBRB among couples from early conception until six months postpartum. A qualitative study using focus group discussions was used to identify determinants of changes in EBRB during pregnancy and in the early postpartum period, and to provide knowledge on how future intervention strategies targeting excessive weight gain should be developed. The first two studies of the PhD research project (STUDY 1 & 2) focused on assessing changes in body weight, body composition and EBRB of both women and men from the first trimester of pregnancy up to six months postpartum. Through a longitudinal dyadic confirmatory factor analysis model, predictors of body composition (i.e., body mass index (BMI), body fat percentage and waist circumference) of 144 couples (i.e., women and men) were investigated (STUDY 1). These results revealed unhealthy changes (i.e., increases for all three predictors) inmaternal body composition from early pregnancy up to six weeks postpartum, which then slightly restored, but still remained above baseline values at 6 months postpartum. For men, unhealthy changes in body composition were described from the beginning of pregnancy up to six weeks postpartum, which then stabilized, but remained above early pregnancy values. STUDY 2 revealed that maternal fruit intake decreased, while alcohol intake increased at six months postpartum compared to baseline (12 weeks of gestation). No changes in dietary intake were described for men. Maternal SB decreased and both maternal and paternal light intensity PA (LIPA) increased from 12 weeks of gestation to six months postpartum. Maternal moderate to-vigorous intensity PA (MVPA) decreased from 12 weeks of gestation to six weeks postpartum, but restored to the initial level at six months postpartum. Men’s MVPA decreased at six months postpartum compared to baseline. Maternal changes in BMI during the transition to parenthood were negatively associated with household family income and changes in fruit group intake, and positively associated with gestational weight gain (GWG). For men, changes in BMI were associated with changes in intake of foods to be avoided (i.e., sugary drinks, sweet and salty snacks, sauces, sweet spreads and processed meat products). In men, there were no associations observed for changes in BMI with changes in PA or SB. The third study (STUDY 3) focused on the association between parental characteristics at the beginning of pregnancy and weight and length growth trajectories of their offspring. Results showed a positive association with GWG, a negative association with maternal PA and a positive association with paternal SB and the weight growth trajectories of the daughters in the first year after birth. No associations were observed with length growth trajectories, or with growth trajectories of the boys. This highlights the influence of both parents’ lifestyle on their offspring, and thus the need to include both women and men in (pre-)pregnancy lifestyle interventions. In a next stage of the project, expectant and first-time parents were interviewed during 13 focus group discussions. Based on these discussions six frameworks giving an overview of changes in EBRB during the pregnancy and the postpartum period were developed (STUDY 4 & 5). Participants described one or more changes in EBRB during both periods (e.g., changes in food choices or type of activities, quantity and frequency of eating and activity occasions, time and place of eating and activities). Four main levels of determinants of changes in EBRB were described, namely, (1) the individual level, including psychological (e.g., ‘health consciousness’), situational (e.g., ‘effort and convenience’) and biological (e.g., ‘discomfort’); (2) the interpersonal level (e.g., ‘social influence’), (3) the environmental level, including micro- (e.g., ‘product price’) and meso/macro (e.g., ‘home/environment food availability’) and the policy level (e.g., ‘maternity leave regulations’). Many determinants were mentioned during both (e.g., ‘food/PA knowledge’) or just one investigated period (e.g., ‘physiological changes’ during pregnancy, ‘influence of the baby’ during the postpartum period). Determinants acting as barriers (e.g., ‘time constraints’) or facilitators (e.g., ‘being a role model’) were identified. Finally, some determinants were described by both parents (e.g., ‘self-regulation’), whereas others were mentioned by women (e.g., ‘(perceived) food/PA safety’) or men (e.g., ‘other priorities’) only. In a sixth study (STUDY 6), the influence of the partner – described at the interpersonal level –was further investigated. The relationship between perceived partner support and dietary (i.e., fruits and vegetables and the ‘avoidance food group’) intake and PA was studied by an Actor Partner Interdependence Model for distinguishable dyads. Perceived support from male partners was significantly associated with women’s own MVPA levels as well as the MVPA levels of the men. Male partners can thus act as significant facilitators for women, and might be an important target when promoting MVPA during pregnancy. Furthermore, in order to develop feasible interventions, the defined determinants of changes in eating behavior during the pregnancy and the postpartum period were rated by first-time parents and experts (STUDY 7). Based on the experts’ rating in terms of modifiability, relationship strength and population-level effect, a ‘priority for research’-score was generated. This was put next to the most important determinants defined by the parents. Focus must go to food education in a broad sense taking into account aspects such as health consciousness, food safety, healthy eating habits and self-efficacy skills and incorporating the social and home food environment. Finally, we aimed to identify needs and wishes of expecting and first-time parents for EBRB interventions during the transition to parenthood (STUDY 8). A checklist with recommendations and suggestions, divided over five main categories (i.e., ‘what’, ‘how’, ‘when and how much’, ‘where’, ‘for and from whom’) for the development of future interventions was established. Personalization of information and timing, reachability, accessibility, communication style and (online) professional support have to be taken into account when developing and delivering the intervention. Altogether, the findings from this PhD research project indicate that both parents experience significant changes in body weight, body composition and EBRB during the transition to parenthood. These changes are influenced by several individual, interpersonal, environmental and policy-related determinants. In this respect, it is important to adequately support couplesto obtain or maintain a healthy body weight and lifestyle by using a multilevel couple- or family based approach. The developed frameworks (STUDY 4 & 5) and checklist (STUDY 8) can be usedas such by other researchers, healthcare providers, or policy makers involved in the development of lifestyle interventions during the pregnancy and the postpartum period.
Original languageEnglish
QualificationDoctor in Movement and Sport Sciences
Awarding Institution
  • Vrije Universiteit Brussel
  • KU Leuven
  • Aerenhouts, Dirk, Supervisor
  • Deliens, Tom, Supervisor
  • Devlieger, Roland, Supervisor, External person
  • Bogaerts, Annick, Co-Supervisor, External person
Award date10 Oct 2022
Publication statusPublished - 2022


  • Transition to parenthood
  • body weight
  • body composition
  • Energy balance related behaviour


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