Harvard studies effect of obesity on male fertility

Harvard Study Review Concludes Excess Weight a Threat to Sperm Production

Pregnant women often experience irresistible hunger cravings, sometimes at all hours of the day and night. These kinds of cravings can lead to a substantial, and temporary, weight gain for the mother -- and also for the father, who often climbs on the impulse-eating bandwagon in a “binging-loves-company” move, since gaining a few extra pounds in solidarity with his partner can seem both harmless and supportive.

At any given time, though, men classified as obese are at a greater risk for infertility. In fact, researchers in France have discovered that obese men are likely to have lower sperm counts than men of normal weight. They also might not have any viable sperm at all.

The researchers concluded, "These data strongly suggest that excess body weight affects sperm production."

After the French researchers released their information, Jorge Chavarro, assistant professor of nutrition and epidemiology at Harvard School of Public Health (HSPH), co-authored a review of their findings, which included data from 14 previous studies. The combined sampling size of all of the studies totaled approximately 10,000 men.

Roughly 25 percent of the 10,000 subjects were found to have a low sperm count. A different analysis showed that 250 of nearly 7,000 men produced no sperm at all.

Men with a few extra pounds were 11 percent likelier to wind up with lower sperm counts. They were also 39 percent likelier to produce no sperm than their normal-weight counterparts, according to an analysis of the data by Sebastien Czernichow and his co-workers at the Ambrose Pare Hospital, Boulogne-Billancourt. 

However, obese men were 42 percent likelier to produce a low sperm count than their normal-weight counterparts and 81 percent likelier to have ejaculate without any sperm.

The researchers theorized that several factors could have led to their findings. One example: Male hormones could possibly become transformed into estrogen in fat tissue, impacting the production of sperm.

"More fat tissue, more estrogens," said Czernichow.

The team also speculated as to whether excess fat in the stomach and hips could lead to an overheated scrotum.

While Chavarro wasn’t able to prove that excess weight will cause problems for males trying to conceive, he nonetheless told Reuters, “In general you expect that men with lower sperm counts will have a greater frequency of difficulty conceiving than men with higher sperm counts.”

Shortly after the Harvard review was published, Dr. Paul Turek, an internationally recognized thought leader in the area of men’s reproductive healthcare, weighed in.

An advocate of the theory that “sperm production is an engine that really wants to run hard and fast,” Turek cited another Harvard study, the first of its kind at the time, that indicated a significant contributor to the obesity problem in men is diet.

Or, as he succinctly put it, “Junk in means waistlines out.”

While the sample size was only 99 subjects, 71 percent of whom were obese or overweight, the Harvard researchers still found that men who consumed high amounts of saturated fats had lower sperm counts. And that men who ate omega-3 polyunsaturated fats — those typically found in plant oils and fish — were likelier to have sperm of better quality.

Turek noted that the study did not cover other conditions that could impact sperm quality (such as heart disease, sedentary lifestyles, and diabetes), it was clear that “dietary fats are now key suspects in the link between obesity and infertility. In other words, sperm are feeling the weight of obesity.”

As anyone who has ever gained weight knows too well, those higher numbers on the bathroom scale can come as a surprise, particularly when metabolism tends to slow down with age but appetite doesn’t. So if you are thinking about your legacy, ideally you should focus on getting in shape before using Legacy’s services.

Khaled Kteily