A correlation between obesity and male fertility has been observed in a few clinical studies. Normal weight men appear to have higher sperm concentrations and sperm motility when compared to obese men, suggesting that weight loss might improve sperm function. However, there also are reported cases of severe male factor infertility following weight loss surgery in previously fertile men. The aim of this study is to determine if there are differences in the semen analyses and hormone levels of men obtained before and after undergoing weight loss (bariatric) surgery.