Two separate research teams looked at the effect of diet on sperm, and concluded that what a man eats can have an impact on his offspring. One team studied the effect of a high fat diet and the other a low protein diet and although they used mice for their work, researchers believe that the results in humans are likely to be similar.
When the male mice were fed a high fat diet, their offspring’s resistance to insulin and glucose intolerance were affected. When they were fed a low protein diet, the researchers reported changes to the genes that are responsible for the development of stem cells. The two papers were both published in the journal Science and you can read more about them here