"In our study population, we found that lower testosterone levels and diminished ratings for sexual quality of life were correlated with increased BMI," Hammoud said.

On the up side, the study's authors found that gastric bypass surgery can help reverse those ills. Men's Sex Lives May Suffer as Waistlines Expand -- The more obese a man, the greater his hormonal changes and the worse his sex life, a new study finds. The participants also filled out questionnaires about the quality of their lives. "Previous studies have found that obesity is correlated to lower sperm count and can be associated with infertility, but we wanted to know if obesity was biologically associated with an unsatisfying sex life, and if so, could it be reversible," the study's lead Kyle Hammoud, of the University of Utah, said in an Endocrine Society news release.

"Our results show that the answer to both questions may be yes." The researchers checked the weight, body mass index (BMI) and reproductive hormone levels of 64 obese men at the start of the study and again two years later, after some of them had what's known as Roux-en-Y gastric bypass surgery.