Poor diet does more than just shorten your lifespan. Being overweight or eating too much junk food can also lower your sperm count. A preliminary study of men who visited a fertility clinic found that those who ate a diet high in saturated fat—such as the meat and dairy served at fast food restaurants—had 43% fewer sperm, as well as a 38% decrease in the concentration of sperm. On the other end of the spectrum, men who ate more omega-3 fatty acids—found in fish and plants such as flax seed—had more sperm with a normal structure. While having some misshapen sperm is normal, too many can affect a man’s fertility. None of the men in the study had a sperm count below the “normal” level set by the World Health Organization, but the connection between sperm count and diet was strong. A separate study found a connection between being overweight and lower sperm counts, as well as infertility. While the first study looked at only 99 men, this one included almost 10,000 volunteers. The researchers found that, compared to normal weight men, more overweight and obese men had low sperm counts. In addition, almost 7% of obese men were infertile, compared to 2.6% of normal weight men. Diet has already been shown to play a role in many diseases, such as heart disease, cancer and type 2 diabetes. These new studies, though, show that what you eat may also affect your ability to have children.