Overweight and obese men are more likely to produce no sperm or to have a lower sperm count than their normal weight peers, according to a study published by a team of French researchers and the Obesity-Fertility Collaborative Group in the "Archives of Internal Medicine" on March 12, 2012.
Dr. Sébastien Czernichow of the Ambroise Pare Hospital, Boulogne-Billancourt, and his colleagues reviewed the results of 14 studies that examined sperm count in ejaculate samples taken from obese, overweight and normal weight men.
The researchers found that obese men were 81 percent more likely to produce no sperm than normal weight men. Obese men were 42 percent more likely to have a low sperm count than normal weight men.
Overweight men were 39 percent more likely to produce no sperm than normal weight men and were 11 percent more likely to have a low sperm count.
The researchers offered several theories to explain why men's increased weight may lower or stop sperm production. Extra fat carried on men's stomachs and hips can raise the temperature of their scrotums, possibly making it too hot for sperm to survive.
A second theory suggests that fat tissue changes male hormones into estrogen, a female sex hormone, disrupting steps needed for the body to make sperm.
The French study's results support the findings of a different study released on February 2, 2012 in the "BJU International," an international urology journal, by a group of Brazilian researchers at Sao Paulo Federal University. That study found that overweight men's sperm was damaged and less mobile.
A high intake of saturated fats in a man's diet can cause a low sperm count, according to a study that appeared on March 13, 2012 in "Human Reproduction," produced by American researchers associated with Harvard Medical School and other U.S. institutions.
