The dietary choices fathers make before conception and during pregnancy have largely been absent from prenatal health conversations — an oversight this research begins to challenge. While maternal nutrition dominates clinical guidance, emerging evidence suggests paternal diet may independently shape offspring outcomes through epigenetic and seminal fluid mechanisms, making this finding relevant to anyone in or planning a reproductive-age household.
This prospective cohort study, nested within a Brazilian randomized controlled trial, followed 43 father-mother-newborn triads, focusing exclusively on the control group of pregnancies where mothers had overweight. Paternal ultra-processed food (UPF) intake, estimated via two 24-hour dietary recalls and classified using the NOVA framework, averaged 30% of total energy intake. After adjustment via directed acyclic graphs to control for confounders, each percentage-point increase in paternal UPF energy share was associated with higher birth weight (β = 12.81 g per unit increase), a greater ponderal index at birth, and larger supra-iliac and thigh skinfold measurements. Notably, no statistically significant association emerged with overall neonatal adiposity estimates derived from the prediction model.
The mechanisms here are biologically plausible but remain speculative. Paternal diet can alter sperm epigenetics — particularly DNA methylation and small non-coding RNA profiles — in ways that influence embryonic gene expression related to metabolic programming. Diets high in ultra-processed foods are linked to elevated inflammatory markers and oxidative stress, both of which could compromise sperm quality and epigenetic fidelity. However, the critical limitation is sample size: with only 43 triads, this study is underpowered for robust causal inference, and the confidence intervals are wide. The cohort was also drawn from a specialized clinical population — overweight pregnant women in Brazilian primary care — which may limit generalizability. This is an incremental but thought-provoking signal that warrants replication in larger, more diverse cohorts before any clinical guidance shifts.
