Father's Diet Before Pregnancy May Influence Baby's Growth and Body Fat: Study - Video

Dad's diet before pregnancy may shape a baby's health-even before conception.

A new study, published in Nutrition Research, suggests that what fathers eat before pregnancy may influence their baby's birth weight and body fat. Researchers found that fathers who ate more ultra-processed foods were more likely to have babies with higher birth weights and more fat around the thighs and waist. These early changes may increase the risk of heart disease, obesity, and type 2 diabetes later in life.

The study included 43 families (father, mother, and newborn) in Brazil.

Ultra-processed foods include products such as soft drinks, packaged snacks, cookies, processed meats, and other heavily processed foods that are often high in sugar, unhealthy fats, salt, and additives but low in nutrients.

Researchers believe these foods may affect the father's sperm health before conception. A diet high in ultra-processed foods can increase inflammation in the body and cause epigenetic changes—chemical changes that affect how certain genes work without changing the DNA itself. These changes can be passed to the baby.

One important gene, called IGF-II, is inherited only from the father and plays a key role in fetal growth. Previous research suggests that a father's diet can influence how this gene functions.

Interestingly, the researchers found a different pattern in mothers. Eating more ultra-processed foods during early pregnancy was linked to lower birth weight, shorter length, and smaller head size in babies, possibly because these foods provide fewer nutrients needed for healthy placental development.

Although the study was small, the findings highlight that a father's nutrition matters just as much as a mother's when planning a pregnancy.

The researchers say larger studies are needed to confirm these results. However, they believe future family planning advice should encourage both parents to eat a healthy, balanced diet before conception to give their baby the best possible start in life.

REFERENCE: Carvalho, M. R., et al. (2026) A higher paternal ultra-processed food consumption is directly associated with parameters of neonatal anthropometry. Nutrition Research. DOI: 10.1016/j.nutres.2026.04.015.