Obesity affects male fertility

Overweight and obese men have been reported to have lower sperm counts and hormonal changes leading to infertility. Researchers from the Finnish Institute of Occupational Health in Helsinki and National Institute of Environmental Health Sciences (NIEHS) in Research Triangle Park, North Carolina found that every excess 10 kilograms, or 20 pounds, might reduce a man's fertility by 10 percent. The researchers analysed couples participating in the Agricultural Health Study who had attempted pregnancy over the past four years. The analysis was limited to couples for whom the wife was younger than 40. The researchers compared the men's body mass index (BMI), a measure of weight in relation to height, to pregnancy success. A BMI of over 25 is considered overweight. Infertility was defined as failure to become pregnant after 12 months of unprotected intercourse. It was found that fertility was lower among men with BMIs of 26 or greater, and decreased as BMI rose. For every three-point increase in BMI, the risk of infertility rose by 12 percent. There are a number of mechanisms by which being overweight could affect fertility in males. For example, excess weight may reduce sperm concentration/count, alter hormonal balance and increase scrotal temperature, or overweight men may simply have lower libidos and less sex than normal-weight men. The findings suggest that preventing obesity might improve men's reproductive health and save medical costs for infertility treatment.