Women are told frequently by experts to maintain healthy lifestyle habits to increase the odds of conception and safeguard the health of a future child. But a new study suggests that men hoping to become fathers should also consider cleaning up their diet and increasing physical activity to improve health outcomes of a baby, even before conception. The study, published Thursday in Cell Metabolism,compared biomarkers in the sperm of obese men versus men who were not overweight. The findings offer a clue into why children of obese dads are also more likely to be obese themselves—and suggests that nongenetic factors like diet can be passed down through sperm.

In a separate, but related study, the researchers followed men who underwent bariatric surgery. They identified some 5,000 DNA changes to the men’s sperm immediately after surgery was completed and even more a year later.