Does male obesity affect fertility?

This study evaluated current evidence of the effects of male obesity on fertility. The study concluded that male obesity is associated with reduced fertility.

Male infertility is the inability to reproduce naturally. It is the cause of approximately 50% of infertility cases. Defective sperm function is the most common cause of male infertility.

Obesity is where a person is carrying too much body fat. It is defined as having a body mass index (BMI, a measure of body fat that takes height and weight into account) of 30 or more. Obesity has been associated with a number of conditions such as diabetes and heart disease. Female obesity is known to reduce fertility, but the role of male obesity in infertility is unclear. The incidence of male inferrtility is increasing and sperm quality is decreasing, but the reasons for this are not known.

This review examined the association between male obesity and infertility. 30 articles, including 115,158 patients, were included in this review.

Obese men were 66% more likely to experience infertility. They were 35% less likely to acheive a live birth when undergoing assisted reproduction (such as in vitro fertilization, when the egg is fertilized by the sperm outside fothe body and then implanted in the uterus). Obese men had a 10% increase in the risk of a non-viable pregnancy (one that did not lead to a live birth). 

Obese men had higher rates of sperm with DNA damage (DNA is the genetic material in humans), abnormal structure and poor function than men with normal weights. 

There was evidence that male fertility rates improved with weight loss and exercise.

The study concluded that male obesity was associated with reduced fertility. The authors also highlighted that semen tests should include analysis on sperm DNA damage, structure and function, particularly for obese men whose results show they should have normal fertility.

The studies didn't consider maternal BMI, so the results could be influenced by the female partner. The findings were from observational studies and showed an association, but didn't show cause. Some studies were not comparable.

If you are having trouble conceiving, discuss with your doctor whether weight may be a factor.