While a drop in libido is often associated with aging in women, it’s not just a female issue. Around 26 percent of men over 70 report a loss of sexual desire as well. Sex isn’t just about reproduction — physical intimacy fosters emotional connection, reduces stress, boosts the immune system, and generally improves mood. Understanding what affects our libido can reveal how lifestyle changes might enhance our sex drive and relationships.
Age-related libido changes are seen across mammalian species. For example, older mice also show a decline in sexual activity, leading to lower offspring production.
Researchers from the German Center for Neurodegenerative Diseases (DZNE), alongside teams from Qingdao University and the University of Health and Rehabilitation Sciences, initially set out to investigate how intermittent fasting in male mice might affect their offspring. However, their study, published in Cell Metabolism, uncovered something unexpected: long-term fasting increased sex drive across all age groups. Their hypothesis? A change in neurotransmitter concentrations in the brain, which could potentially be used to treat libido loss in humans.
Intermittent Fasting and Serotonin
Calorie restriction, such as intermittent fasting, offers benefits beyond fat loss, including improved metabolic function, lifespan, and heart health. By reducing food intake for specific periods, fasting can manage weight and prevent some health issues.
One way intermittent fasting may influence libido is through serotonin, a neurotransmitter produced primarily in the gut. Serotonin plays a role in regulating sexual behavior in the brain, often inhibiting sexual desire. It’s made from tryptophan, an essential amino acid that we must get from our diet. If fasting leads to less tryptophan intake, it could result in lower serotonin levels in the brain, potentially reducing its inhibitory effects on libido.
Read More: Should You Use Serotonin Supplements?
Less Food, More Sex
In the study that sparked this hypothesis, male mice were put on an intermittent fasting regimen: 24 hours of unlimited food, followed by 24 hours of fasting. After 22 months, the researchers introduced the fasting mice to females who hadn’t fasted.
Though reproductive outcomes weren’t the original goal, the researchers were surprised to find that the fasting males produced an unusually high number of offspring. Upon closer examination, they ruled out effects on the males’ reproductive organs or hormones.
“Eventually, we realized: it is a matter of behavior. The fasting males had significantly more sexual contacts than mice that could eat freely. In other words, these animals had an unusually high frequency of mating and, as a result, an unusually high number of offspring for their age. Their mating behavior more than compensated for the age-related physiological limitations,” said study lead Dan Ehninger in a press release.
Further investigation revealed that all the sexually active, fasting mice shared one common factor: significantly lower serotonin levels.
Potential of Fasting in Humans
“For intermittent fasting to increase sex drive, it takes some time,” said Yu Zhou, professor from the Qingdao University, in the news release. “Based on our experiments, the minimum duration appears to be somewhere between six weeks and six months.”
To apply these findings to humans, more studies are needed, of course. However, the similarity between serotonin’s role in sexual behavior in both mice and humans — and the known side effects of certain antidepressants that increase serotonin and lower libido — makes it plausible to consider fasting as a potential solution, not just for men but for women as well.
“In my opinion, it would make sense to investigate this in more detail,” said Ehninger in the release, “I see potential for therapeutic application. A lack of sexual desire is not necessarily perceived as problematic — but some people suffer from it. Fasting could potentially serve as a useful addition to existing treatment options.”
Read More: The Weird Quirks of the Male Libido
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Having worked as a biomedical research assistant in labs across three countries, Jenny excels at translating complex scientific concepts – ranging from medical breakthroughs and pharmacological discoveries to the latest in nutrition – into engaging, accessible content. Her interests extend to topics such as human evolution, psychology, and quirky animal stories. When she’s not immersed in a popular science book, you’ll find her catching waves or cruising around Vancouver Island on her longboard.
