Turns out dads are also eating for two. A study published December 3 in Cell Metabolism reveals that a man's weight affects the heritable information contained in sperm. The sperm cells of lean and obese men possess different epigenetic marks, notable at gene regions associated with the control of appetite. The comparisons, which included 13 lean men and 10 obese men, offer one biological explanation for why children of obese fathers are themselves more predisposed to obesity.

In the next phase of the study, the investigators tracked 6 men undergoing weight-loss surgery to see how it affected their sperm. An average of 5,000 structural changes to sperm cell DNA were observed from the time before the surgery, directly after, and one year later. More needs to be learned about what these differences mean and their effects on offspring, but it is early evidence that sperm carries information about a man's health.