A father's health before conception may play a role in the future health of his children, according to new research from Washington State University. The study helps answer a long-standing question about how a father's diet, metabolism, and overall health can influence the next generation. Scientists have known for years that factors such as obesity, poor diet, and metabolic disease in fathers can increase the risk of metabolic problems in their children. What has been less clear is how that information is carried in sperm and passed along. Researchers at WSU found evidence suggesting the process begins in the testis, where sperm are produced, rather than later as sperm mature and travel through the male reproductive tract. "We wanted to understand where that heritable information comes from, if a father's metabolic condition can affect his offspring," said Wei Yan, director of the WSU School of Molecular Biosciences and the study's senior author. The research challenges a theory that sperm mitochondria, the structures that produce energy in cells, play a major role in transmitting that information. The team found mature mouse sperm contain very little mitochondrial DNA, making that explanation unlikely. Instead, the findings suggest the biological information linked to a father's metabolic health is established earlier during sperm development. To reach that conclusion, researchers used a laboratory technique called intracytoplasmic sperm injection, or ICSI, which allowed them to compare sperm taken directly from the testis with sperm collected later in the reproductive process. The researchers found that sperm taken directly from the testis could still pass diet-related metabolic traits to offspring. That finding supports the idea that the information originates before sperm leave the testis. Yan said the results shift attention to an earlier stage of sperm development and provide new insight into how a father's health may influence the next generation. Researchers emphasized that the findings do not mean children are destined to develop metabolic disease. Instead, the study identifies one possible biological pathway that could affect disease risk. Yan said a better understanding of paternal health could help inform future efforts focused on prevention, reproductive health, and early-life disease risk. The findings also suggest that improving a father's health before conception could potentially benefit both fathers and their future children. The study reflects a growing focus on the role fathers play in reproductive health, an area that has traditionally centered on maternal health.