Scientists May Have Discovered Simple Cure for Low Sex Drive

Intermittent fasting is often associated with weight loss and metabolic health, but a new study suggests it may also boost sex drive too. Researchers found that male mice subjected to long-term intermittent fasting (IF) showed significantly increased mating behavior, potentially pointing to a new approach towards treating low libido in humans. The study was undertaken by an international team of researchers from the German Center for Neurodegenerative Diseases (DZNE) as well as China's Qingdao University and the University of Health and Rehabilitation Sciences. Their findings suggest that fasting lowers serotonin levels in the brain, reducing inhibitory effects on sexual behavior.

The study initially set out to examine how fasting affects the offspring of male mice, but researchers noticed something unexpected: senior male mice that had fasted produced an unusually high number of offspring. Surprisingly, this increase wasn't due to changes in sperm quality or hormone levels—but rather a dramatic rise in sexual activity. "It was a bit of detective work to uncover the real cause," said lead researcher Dr. Dan Ehninger of DZNE. "Eventually, we realized it was about behavior—the fasting males had significantly more sexual contacts than mice that could eat freely." The male mice were placed on a 24-hour intermittent fasting cycle, alternating between a full day of eating and a full day of water only. After several months were kept in male-only housing the specimens were later introduced to female mice. Those that had fasted for at least six months exhibited significantly more sexual activity compared to the control group. The key biological mechanism behind this effect appears to be a drop in serotonin levels. The neurotransmitter, which plays a role in mood regulation, is also known to inhibit sexual behavior. Since serotonin production depends on tryptophan—an amino acid obtained from food—fasting led to a deficiency, which in turn reduced serotonin levels. "These mice were, so to speak, sexually uninhibited, the usual regulatory restraint was diminished," Ehninger said. While this study specifically examined a strict 24-hour fasting/24-hour feeding cycle, Ehninger acknowledged that other fasting methods such as time-restricted eating (16:8 fasting, for example) or caloric restriction might produce similar results. "We did not investigate other dietary restriction methods such as time-restricted feeding or chronic caloric restriction. It remains an open question whether these alternative fasting paradigms would induce similar neurochemical and behavioral changes," he told Newsweek. The researchers believe similar mechanisms could exist in humans, as serotonin plays a well-documented role in regulating libido. Antidepressants like SSRIs, which increase serotonin, often cause a reduced sex drive as a side effect, further supporting the link between serotonin levels and libido. Ehninger sees strong potential for translating these findings into human research, as serotonin regulation and its impact on libido are well-documented in humans. "Human trials represent a logical and timely next step to determine whether IF can produce similar enhancements in libido, particularly in aging men or individuals experiencing reduced sexual desire, such as those with hypoactive sexual desire disorder," he told Newsweek. While human studies are needed, Ehninger sees potential for fasting as a therapy for hypoactive sexual desire disorder (HSDD), a condition characterized by a lack of sexual desire, particularly in older adults. "Fasting could potentially serve as a useful addition to existing treatment options," he said.Do you have a tip on a health story that Newsweek should be covering? Do you have a question about intermittent fasting? Let us know via science@newsweek.com.

Reference

Xie, K., Wang, C., Scifo, E., Pearson, B., Ryan, D., Henzel, K., Markert, A., Schaaf, K., Mi, X., Tian, X., Jia, J., Wang, M., Bonn, S., Schölling, M., Möhl, C., Bano, D., Zhou, Y., & Ehninger, D. (2025). Intermittent fasting boosts sexual behavior by limiting the central availability of tryptophan and serotonin. Cell Metabolism, 37. https://doi.org/10.1016/j.cmet.2025.03.001