[rhinoceraptor]

I get that it's slightly esoteric, but this is all pretty basic biochem/endocrinology.

Here's a small study that demonstrates that losing weight can increase fertility:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3177768/

Additionally, this mechanism is why drugs like clomifene and anastrazole work for male infertility.

[teachrdan]

Ha, "pretty basic biochem/endocrinology", followed by a link to a 10-year-old study of 43 men which concludes:

"This study found obesity to be associated with poor semen quality and altered reproductive hormonal profile. Weight loss may potentially lead to improvement in semen quality. Whether the improvement is a result of the reduction in body weight per se or improved lifestyles remains unknown."