Childhood adversity trajectories and weight status in young adult men: a register-based study including 359,783 Danish men

Overweight and obesity are rising globally and carry serious health and socioeconomic consequences. Weight status in young adulthood is particularly predictive of later health outcomes, and pathways to adult obesity may be established during childhood. Adverse childhood experiences—stressful or traumatic events that disrupt a child’s sense of safety and stability—are common and have been linked to a range of adverse adult health outcomes. Prior studies and reviews suggest that childhood adversity increases the risk of adult overweight and obesity via biological, stress-related, and behavioral pathways, with theories such as the Food Insecurity Hypothesis and the Adiposity Force Theory proposing evolutionary mechanisms predisposing to fat storage under adverse conditions. However, much prior work used small, selected samples, retrospective single-adversity measures, and self-reported BMI, and often focused only on obesity rather than the full weight spectrum. Some evidence also points to associations with adult underweight, though results are inconsistent. The present study investigates whether prospectively derived trajectories of childhood adversity from ages 0–15 years are associated with underweight, normal weight, overweight, and obesity in young adult Danish men. It was hypothesized that adversity exposure would be associated with greater risks of underweight, overweight, and obesity compared with low adversity.

Systematic reviews and large studies have reported that exposure to multiple adverse childhood experiences is associated with higher odds of adult overweight/obesity (e.g., pooled ORs around 1.39–1.46). Longitudinal and dose-response evidence indicates increasing obesity risk with greater adversity counts, and effects may be stronger in adulthood than in youth, suggesting latency in manifestation. Proposed mechanisms include chronic stress responses (e.g., HPA-axis dysregulation), sleep disturbances, behavioral factors (poor diet quality, low physical activity), and mental health sequelae (e.g., depression) that influence eating and weight. Evolutionary hypotheses (Food Insecurity Hypothesis; Adiposity Force Theory) suggest adversity-related cues may biologically promote fat storage. Evidence on adversity and underweight is mixed but some studies link adversity to underweight and unhealthy weight control, potentially via mental health problems, maladaptive coping, and disordered eating. Prior studies often relied on retrospective adversity reports, self-reported BMI, single adversity measures, and did not cover the full weight spectrum, underscoring the need for large, prospective, population-based studies with measured BMI and comprehensive adversity trajectories.

Design and data sources: A prospective, register-based cohort study linking the Danish Life Course Cohort (DANLIFE; all children born in Denmark 1980–2015) with the Danish Conscription Registry (DCR; objective health assessments at draft board examinations). The analytic cohort included males born 1988 or later (to ensure availability of height/weight from 2006 onwards) who could be followed to age 15 for adversity data and had measured BMI at draft board examination between ages 18–26 years, yielding N = 359,783.

Exposure: Childhood adversity trajectories (ages 0–15) previously derived in DANLIFE using group-based multi-trajectory modeling (zero-inflated Poisson with cubic functions; Stata TRAJ) on yearly counts across three domains: material deprivation (poverty, parental long-term unemployment), loss/threat of loss (parental or sibling somatic illness or death), and family dynamics (foster care placement, maternal separation, parental alcohol/drug abuse, parental or sibling psychiatric illness). Five mutually exclusive trajectory groups were identified and assigned by maximum posterior probability: (1) Low adversity; (2) Early material deprivation (high early material deprivation, decreasing thereafter); (3) Persistent material deprivation (high across childhood); (4) Loss or threat of loss (increasing across childhood); (5) High adversity (high and increasing in all three domains).

Outcome: Body mass index (BMI) at draft board exam measured by medical staff with standardized procedures. BMI categorized by WHO definitions: underweight (<18.5), normal weight (18.5–24.9), overweight (25.0–29.9), obesity (≥30.0).

Covariates: Birth year; age at draft exam (continuous; modeled with splines); parental country of origin (Western vs non-Western); maternal age at birth (<20, 20–30, >30 years); parental cardiometabolic disease in the 3 years before birth (ischemic heart disease, cerebrovascular disease, congestive heart failure, peripheral vascular disease, type 1 or type 2 diabetes); preterm birth (<37 weeks vs ≥37 weeks); size for gestational age (small <10th, average 10th–90th, large >90th percentile); parental education at birth (low <10 years, medium 10–12 years, high >12 years).

Statistical analysis: Descriptive statistics characterized participants by adversity trajectory. Multinomial logistic regression estimated risk ratios (RR) for underweight, overweight, and obesity (each vs normal weight), using the low adversity group as reference. Model 1 (main) adjusted for birth year and age at draft exam with flexible splines, parental origin, and maternal age. Supplementary Model 1 additionally adjusted for parental cardiometabolic disease; Supplementary Model 2 further included size for gestational age and preterm birth; Supplementary Model 3 (addressing socioeconomic confounding/overlap) additionally adjusted for parental education. Robustness across models was evaluated. Results were presented as RRs with 95% confidence intervals.

• Sample distribution across adversity trajectories: low adversity 58.2%, early material deprivation 20.1%, persistent material deprivation 9.7%, loss/threat of loss 9.4%, high adversity 2.6%. • Prevalence of weight categories overall: underweight 5.2%, normal weight 66.5%, overweight 20.8%, obesity 7.5%. In the high adversity group: underweight 6.3% and obesity 9.6%; in the low adversity group: underweight 5.0% and obesity 6.5%. • Main adjusted model (birth year, age at exam, parental origin, maternal age): All four adversity groups had higher risks of underweight, overweight, and obesity compared with the low adversity group. The high adversity group showed the strongest associations with underweight (RR 1.44; 95% CI 1.32–1.58) and obesity (RR 1.50; 95% CI 1.39–1.61). The largest RR for overweight was observed for persistent material deprivation (RR 1.14; 95% CI 1.11–1.17) vs low adversity. • Results were similar after additional adjustment for parental cardiometabolic disease and for perinatal factors (size for gestational age, preterm birth). • After adjustment for parental education, RRs were attenuated for all adversity groups, particularly the high adversity group; notably, high adversity was associated with slightly lower risk of overweight (RR 0.90; 95% CI 0.85–0.95) vs low adversity, while associations with underweight persisted.

The study addressed whether prospectively measured childhood adversity trajectories are associated with the full spectrum of weight status in young adult men. Findings demonstrated that adversity exposure from ages 0–15 increased the risk of both ends of the BMI spectrum—underweight and obesity—and, to a lesser extent, overweight, in young adulthood compared with low adversity. These associations were robust to adjustment for demographic, parental origin, and early-life health factors, suggesting an independent effect of adversity beyond measured confounders. Attenuation after adjusting for parental education highlights socioeconomic overlap, particularly with material deprivation dimensions, yet persistence for underweight suggests potentially distinct mechanisms driving low and high BMI outcomes. The results align with prior literature linking childhood adversity to adult obesity and extend it by using large-scale, prospective registers with measured BMI and trajectory-based adversity. Potential mechanisms include biological stress responses (e.g., HPA-axis dysregulation), evolutionary adaptations to perceived resource insecurity, and behavioral and psychological pathways (diet quality, physical activity, depression). The modest association with overweight versus stronger associations with underweight and obesity suggest adversity may be more strongly tied to extremes of weight status.

In this large population-based cohort of Danish men, childhood adversity trajectories from 0 to 15 years were associated with higher risks of underweight, overweight, and obesity at ages 18–26 compared with low adversity. Young adulthood is a critical phase for weight trajectories, and these findings underscore the importance of addressing early-life adversity within social and familial contexts as potential targets for public health intervention to promote healthy weight across the lifespan.

Key limitations include: lack of direct measures of certain adversities (e.g., family violence, sexual abuse, neglect) and school social dynamics (e.g., bullying); no information on individual-level manifestations of adversity; absence of parental BMI, a strong genetic and environmental predictor of offspring BMI (parental cardiometabolic disease was used as a crude proxy and had minimal impact on estimates); reliance on BMI only without other adiposity indicators; and inclusion of men only, limiting generalizability and potentially underestimating associations compared with women in some prior studies. The adversity trajectory approach did not capture all possible adversity types, and residual confounding by socioeconomic factors may remain despite adjustments.