Does weight loss surgery impact semen parameters?

This study looked at the effects of obesity and weight loss surgery on male fertility. It found that six months after weight loss surgery, hormone levels improved but sperm count was greatly reduced.

Obesity changes many aspects of metabolism, including hormone levels. Fat cells create estrogen and can reduce testosterone. Additionally, many people with obesity have higher levels of the hormone insulin, which controls blood sugar. Resistance to insulin causes other hormonal changes. 

Men with obesity often have low testosterone and low sperm count. Additionally, men with obesity have higher sperm DNA fragmentation (SDF). SDF is damage to genetic material, which lowers fertility and can increase miscarriage.

Bariatric surgery (BS) is a treatment for obesity that involves surgically altering the stomach and/or small intestines. BS can lead to substantial and sustained weight loss. However, it can also have complications including vitamin deficiencies. It is not clear whether BS can improve fertility for men with obesity.

This study included 42 men with obesity (body mass index over 40 kg/m²). As a comparison, it also included 32 men without obesity (BMI under 35 kg/m²) who had fathered at least two children. All of the men had blood tests of hormone levels and semen samples. 18 men with obesity had BS. They were followed up after six months and compared to 14 of the men with obesity who did not have surgery.

Men with obesity had significantly higher estrogen (estradiol 33.3 vs. 22.0 pg/mL) and lower total testosterone (272.5 vs. 413 ng/dL) compared to non-obese men. Patients with obesity had significantly lower sperm count (82.5 vs. 205.2 million). They also had more SDF.

After BS, patients’ body weight significantly decreased. Patients had lower rates of high blood pressure and diabetes following surgery. Total testosterone levels significantly increased following surgery (604 vs 294.5 ng/dL). SDF improved after surgery. However, sperm count decreased dramatically following surgery (122.8 to 17.0 million). Two patients (11%) no longer produced sperm following surgery (azoospermia).

This study found hormone levels improved but male parameters declined following weight loss surgery in men with obesity.

The type of surgery used by most of these patients, Roux-en-Y gastric bypass, causes more vitamin deficiency than other kinds of weight loss surgery. It is possible that low vitamin levels are connected to the lowered sperm counts. More studies are needed.