Fathers’ Ultra-Processed Food Intake May Affect Babies’ Birth Weight and Size

Ultra-processed food intake may influence a child’s health even before conception, according to a study tracking diet and newborn body measures in Ribeirão Preto, Brazil. Researchers analyzed 43 father-mother-newborn triads from families receiving care through the public health system.

The results link fathers’ higher consumption of ultra-processed foods to increased birth weight and greater fat accumulation in specific neonatal regions, including the thigh and the suprailiac area often described as “love handles.” Because early-life fatness and birth weight are associated with later cardiometabolic risk, the findings suggest a potential pathway to adult disease.

Ultra-processed foods—formulations dominated by food-extracted substances and synthetic additives, with little or no whole foods—account for a substantial share of energy intake in many diets. In this cohort, fathers’ ultra-processed food intake averaged about 30% of total calories, particularly from processed meats, sugary drinks, and cookies.

The investigators propose that such dietary patterns can disrupt sperm biology. Rather than acting only through general nutritional status, a diet rich in ultra-processed foods may create a pro-inflammatory internal environment that affects sperm quality and alters the expression of genes delivered to the embryo.

This gene-level communication is framed through epigenetics: chemical or regulatory modifications that change how genes behave without changing DNA sequence. In the study, altered gene activity is suggested as a mechanism by which paternal diet could shape fetal development.

One highlighted gene is IGF-II, which supports fetal growth and is inherited exclusively from the father. Prior work indicates that dietary habits can influence IGF-related regulation in sperm via DNA methylation, a process involving the addition of methyl groups that can “turn” genes up or down.

Comparisons with maternal diet revealed an opposing association: higher mothers’ ultra-processed food intake early in pregnancy was related to lower birth weight, shorter length, and smaller head circumference. The authors interpret this difference as possibly reflecting effects on placental development and nutrient delivery.

Interestingly, the study did not find an overall increase in total neonatal body fat, but it did detect region-specific fat deposition. That pattern supports the idea that diet quality may influence fetal tissue growth dynamics, not just aggregate adiposity.

Although the sample is small, the study is described as pioneering evidence connecting paternal ultra-processed food intake to neonatal anthropometry, reinforcing the need to include men in family-planning and preconception health guidance.