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Another problem for overweight or obese men: an increased risk of poor sperm quality. Researchers in India found that compared to normal weight men, obesity was associated with lower sperm count, lower volume of semen, lower sperm concentration, poor sperm motility (the movement of sperm), as well as sperm defects. There is some evidence (from other studies and the researchers own work) that there is improvement in sperm quality with weight loss.

The researchers pointed out that other studies have shown that "paternal obesity at conception had deleterious effects on embryo health, implantation, pregnancy, and live birth rates." And that poor sperm quality is a cause of infertility. So.... what do the researchers recommend? Weight loss and exercise, and perhaps bariatric surgery, for obese men having fertility problems due to poor sperm quality. From Medical Xpress: 

As men's weight rises, sperm health may fall

A widening waistline may make for shrinking numbers of sperm, new research suggests. Indian scientists studied more than 1,200 men and found that too much extra weight was linked to a lower volume of semen, a lower sperm count and lower sperm concentration. In addition, sperm motility (the ability to move quickly through the female reproductive tract) was poor. The sperm had other defects as well, the researchers added. Poor sperm quality can lower fertility and the chances of conception.

"It's known that obese women take longer to conceive," said lead researcher Dr. Gottumukkala Achyuta Rama Raju, from the Center for Assisted Reproduction at the Krishna IVF Clinic, in Visakhapatnam. "This study proves that obese men are also a cause for delay in conception," he added.

But in continuing research, the study team is looking to see if losing weight will improve the quality of sperm. Although that study is still in progress, early signs look good that sperm quality improves as men lose weight, Rama Raju said. Recent reports have found that extreme weight loss after bariatric surgery reversed some of the sperm decline, he said.

For the study, Rama Raju and his colleagues used computer-aided sperm analysis to assess the sperm of 1,285 men. Obese men, they found, had fewer sperm, a lower concentration of sperm and inability of the sperm to move at a normal speed, compared with the sperm of men of normal weight. Moreover, the sperm of obese men had more defects than other sperm. These defects included defects in the head of the sperm, such as thin heads and pear-shaped heads.  [Original study.]

 Human sperm. Credit: Wikipedia

That's right - when thinking about having children, don't just focus on the women's age. From Science Daily:

Men's sperm quality declines with age, review of 90 studies confirms

Conflicting evidence about the extent to which men's semen quality declines with age -- likely lowering their fertility -- is being cleared up by new research that has collated and reviewed data from 90 previous studies from around the world.

After conducting a systematic review and meta-analysis of the studies' data, researchers from the University's Departments of Zoology and Anatomy found consistent age-related declines in semen volume and sperm performance and increases in malformed and DNA-damaged sperm. Semen quality is regarded as a proxy for how fertile a male is.

"The effects of declining semen traits with increasing male age have largely been ignored due to inconsistencies in the literature, but our work now suggests that male age affects a variety of traits. It is well recognised that reduced sperm performance can affect pregnancy success, but it is less well known that the quality of the sperm, particularly DNA quality, could affect the development and health of the offspring," Dr Johnson says.

"Our study made no attempt to estimate the rate of decline, but some well-controlled clinic-based studies have observed consistent declines with increasing age, whereas others project declines after age 35 for some traits and after age 40 for others" she says.

"Older males contribute to increased risk of obstetric complications, miscarriage, and offspring disorders such as autism, Down syndrome, epilepsy, and schizophrenia. In addition, increasing male age may be an overlooked component of couple infertility, leading to our increased use and dependency on fertility treatments, such as IVF."

The authors suggest that clinical analysis of the percentage of DNA-fragmented sperm cells and a greater focus on how well sperm swim may lead to better patient outcomes during fertility treatments of aging couples."These are likely more accurate and consistent predictors of a man's fertility status than commonly clinically measured traits such as semen volume, sperm concentration and total sperm count," Dr Johnson says.

Sperm under microscope.
Credit: Fertility Associates Ltd. NZ