What’s the Skinny on Weight and Male Infertility

Posted on by Paul Turek, MD
Effect of Wight on Male Infertility Beverly Hills
The unbearable lightness of being (Courtesy Diana Polekhina, Unsplash)

Ok, so you’re a victim of the “quarantine-19,” the perfunctory weight gain associated with the (very real) stress of COVID. Maybe you pivoted to fast food and dropped your exercise routine. Or you began to relish those end-of-day ‘quarantini’ cocktails now that you’re not commuting anymore. Sure, you’ve been meaning to lose that pandemic weight, but life got really busy again and it hasn’t been easy. Need a little motivation? How’s this: a 5% weight loss (that’s 10 lbs out of 200) is known to hold the following health benefits:

  • Reduces insulin resistance and the risk of prediabetes and diabetes
  • Bumps up good cholesterol (HDL), which protects against heart disease
  • Drops triglycerides, which protects against heart disease
  • Lowers high blood pressure
  • Reduces severity of sleep apnea
  • Lowers risk of cancers including breast, colon, rectum, prostate, and pancreas
  • Reduces fatty liver disease
  • Improves body image

But did you know that your weight can also throw a monkey wrench into your efforts to conceive? In fact, when it comes to weight’s effect on male fertility, both extremes are problematic: being too thin or being overweight can both reduce sperm quantity and quality. But the bulk of evidence links obesity to male infertility.

Tipping the Scales

Using body mass index (BMI) as a measure (the ideal BMI for men being 20-25), a large Danish study showed that overweight men with a BMI > 25 had a 22% lower sperm concentration compared with healthy weight men. Other human and animal studies have confirmed this relationship and have also correlated obesity with reductions in sperm motility, increases in sperm DNA damage and lower testosterone levels. So, it’s clear that sperm don’t work as well in the setting of obesity. But is actual fertility affected by weight? It appears so. Another study showed that for every 20-pound increase in a man’s weight, there is a 10% increase in the chance of infertility. And this held true when other factors that influence results were taken into consideration. It’s as if adding weight starves sperm.

Exactly how does obesity influence sperm and fertility?  One way is through altered sex hormone balance. Testosterone is the “fuel” for the engine (testis) to make sperm. Obesity increases fat stores and fat converts testosterone into female hormones (estrogens). Too much estrogen in men depresses sperm production. Another issue is that the normal 3° temperature difference between the testes and the body proper is lost with obesity, as extra scrotal fat insulates the gonads and overheats the sperm-making machinery. Lastly, it is known that fat-producing cells are pro-inflammatory and more of them could induce a form of chemical imbalance known as oxidative stress within the testis and other genital organs. Added weight then poses a triple assault on male fertility.

A Heavy Weight

An even more compelling reason to keep your weight under control is that recent studies now show that obesity can introduce changes to sperm DNA, termed epigenetic alterations, that may be inherited by offspring. That means that by being overweight, you increase your children’s risk of having obesity and possibly other metabolic disorders. Remember, if it’s in sperm, then it’s gonna be handed down to kids, because that’s what sperm do. Why put your kids at risk of diseases even before they are born? Does that change things a bit for you?

So, to be clear, obesity adversely affects fertility. Another reason to be the best, and most healthy, person you can be, as you are one of your future family’s most important investments.