Weight and Fertility: How Higher BMI Hurts Sperm and Hormones
A meta-analysis of 14 studies with 8,443 men found higher BMI — including overweight and obesity — is linked to poorer sperm quality (shape, movement, concentration, volume, total count) and changes in sex hormones (total testosterone, FSH, LH). BMI should be considered in male fertility checks; lifestyle changes may help but need more study.
Body weight affects more than the waistline. When BMI rises into the overweight and obese range, sperm quality and sex hormones change in ways that can hurt fertility.
Researchers pooled 14 studies with 8,443 adult men. The men were grouped by BMI: 3,467 with normal weight, 3,444 overweight, and 1,532 obese. All studies looked at sperm; four also measured hormones.
Higher BMI was linked to worse sperm shape (normal morphology). Men with higher BMI also had lower total motility and progressive motility, meaning fewer sperm moved well.
Sperm concentration, semen volume, and total sperm count were also lower in men with higher BMI. These measures are key for a man’s chance of helping a partner get pregnant.
Sex hormone levels changed with higher BMI too. Total testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) showed differences between BMI groups. Hormone shifts can affect sperm production and sexual health.
Taken together, higher BMI looks like a clear risk factor for male reproductive health. Doctors should consider weight when checking men for fertility problems.
The good news is weight can often be changed. Diet, exercise, and lifestyle steps may help sperm and hormone levels, but more long-term studies are needed to show how much and how quickly things improve.
Men trying to conceive should talk with their doctor about BMI, lifestyle changes, and fertility testing. Small steps now may improve chances later.