Obesity in men can cause fertility problems

Obese men produce less semen and fewer healthy sperm and should considering losing weight if they want to have children, Scottish researchers said.

A. Ghiyath Shayeb and colleagues at the Aberdeen Fertility Center compared the health records of 2,037 men and found that those of normal weight had higher levels of normal sperm and more semen. Shayeb reported the findings at the annual conference of the European Society of Human Reproduction and Embryology in Barcelona.

"We felt that it was possible that male overweight might contribute to fertility problems, particularly since it is a known risk factor for problems in conceiving among women," Shayeb said in a statement. The findings "suggest that men who are trying for a baby with their partners should first try to achieve an ideal body weight," he said.

Different levels of hormones in obese men, overheating of the testicles because of fat, and diet all may contribute to lower sperm quality, researchers said. To what extent obesity and poor semen quality lead to lower fertility needs further study, Shayeb said. Other research suggests obese men produce more abnormal sperm in which the DNA, the instructions for cell growth and function, are damaged, leading to infertility and more miscarriages.

Male infertility problems may be responsible for up to half of couples' inability to conceive, the U.S. National Institutes of Health estimates.

Semen analysis measures the volume of semen, the number and structure of sperm and their ability to move. Shayeb conducted semen analysis on 5,316 men attending the fertility clinic and had complete body-mass index ratings for 2,037.

BMI reflects a person's weight compared with height. Men in the study with healthiest sperm had an optimal BMI of between 20 and 25.

A person with a BMI between 25 and 30 is considered overweight and those with higher levels are obese.