Intermittent fasting conceptual image Credit: Carol Yepes (Getty Images)
Credit: Carol Yepes (Getty Images)
In a finding that may raise eyebrows for both scientists and couples seeking relationship advice, researchers have discovered that male mice who skip meals show significantly increased sexual interest and activity. The hunger-libido connection, revealed in a study published March 28 in Cell Metabolism, might eventually lead to new approaches for treating low sexual desire in humans.
The research team from Germany’s DZNE (German Center for Neurodegenerative Diseases) and Chinese institutions stumbled upon this revelation while investigating something completely different. They originally set out to examine how intermittent fasting affects offspring, but noticed something unexpected – older male mice on long-term fasting regimens were producing far more babies than their well-fed counterparts.
“It was a bit of detective work to uncover the real cause,” said Dr. Dan Ehninger, research group leader at DZNE and lead author of the study. “Eventually, we realized: it is a matter of behavior. The fasting males had significantly more sexual contacts than mice that could eat freely.”
The research involved a specific fasting protocol where male mice alternated between 24 hours of unlimited food access and 24 hours with only water. This pattern continued for either 6 or 22 months before the males were introduced to females.
What’s particularly notable is that these sexually reinvigorated mice weren’t young studs – many were the rodent equivalent of senior citizens. Despite age-related limitations like reduced sperm quality and lower testosterone levels, their increased mating frequency more than made up for these physiological challenges.
The biological mechanism behind this behavioral change appears to involve serotonin, a neurotransmitter that typically has inhibitory effects on sexual behavior. Researchers found unusually low levels of serotonin in the brains of the fasting mice.
“These mice were, so to speak, sexually uninhibited, the usual regulatory restraint was diminished,” Ehninger explained.
The serotonin reduction stems from a diet-induced deficiency of tryptophan, an essential amino acid that must be obtained through food. Without adequate tryptophan intake, serotonin production decreases.
While the findings are intriguing, they may not appeal to those seeking instant results. The researchers noted that brief fasting periods had no impact on sexual behavior.
“For intermittent fasting to increase sex drive, it takes some time,” said Prof. Yu Zhou, who collaborated on the study. “Based on our experiments, the minimum duration appears to be somewhere between six weeks and six months.”
The fasting mice consumed approximately 15% fewer calories than the control group, with a similar reduction in tryptophan intake. However, researchers remain uncertain whether this specific feeding pattern is required or if other fasting approaches might produce similar effects.
Could these findings translate to humans? Ehninger believes it’s plausible. He points to evidence from medication side effects – specifically how SSRI antidepressants, which increase serotonin levels, often reduce libido as an unwanted consequence.
“In view of this, I consider it very plausible that sexual desire in humans can be influenced by fasting – possibly not only in men, but also in women, since serotonin affects their libido as well,” Ehninger noted.
The research team suggests that fasting could potentially offer a new approach for treating hypoactive sexual desire disorder, a condition affecting many older adults. However, they acknowledge that more targeted human studies are needed before dietary interventions could be recommended as therapy for low libido.
As winter gives way to spring and many people consider lifestyle changes, this research adds an unexpected potential benefit to the already lengthy list of claimed advantages for intermittent fasting. Whether humans might experience similar effects remains to be seen, but the connection between diet and desire continues to be an evolving area of scientific interest.
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