News | Study Finds 24-Hour Cyclic Fasting Increases Libido in Male Mice, Suggesting a New Approach to Low Sexual Desire
A recent study by the German Center for Neurodegenerative Diseases (DZNE), Qingdao University, and the University of Health and Rehabilitation Sciences found that regular 24-hour cyclic fasting significantly increased sexual drive in male mice, possibly by lowering serotonin levels. Published in Cell Metabolism, the study suggests that the mechanism may also apply to humans and could offer a new approach to reduced sexual desire.
Fertility Increased Unexpectedly in a Study Not Focused on Sex
The study initially examined how fasting affects offspring health, not sexual behavior. During the research, however, scientists noticed an unexpected result: older male mice that had fasted long-term produced far more offspring than expected.
Dr. Dan Ehninger, head of the DZNE research team and first author of the study, said: “These mice were equivalent to elderly humans. Their testicular function, sperm quality, and testosterone levels were no better, so their fertility should have declined. Instead, the opposite occurred.”
Further analysis showed that behavior, not physiology, was the key. Older fasting males mated much more often than same-age mice fed without restriction, and their increased sexual activity fully offset the physiological disadvantages of age.
Diet Pattern: Alternating 24-Hour Cycles
Beginning at two months of age, the male mice followed an alternate-day fasting pattern: unrestricted food for one day, then no food and only water the next. This cycle continued for 22 months. They had no contact with females until late in the study, when they were paired with three-month-old females that had never undergone dietary restriction.
Younger males that began fasting at two months and continued for six months also showed stronger sexual motivation than freely fed mice of the same age. Groups that fasted for only a few weeks showed no significant difference.
“This means the effect of fasting on sexual desire takes time to develop,” said Professor Zhou Yu, who led the Chinese research team. “Our data suggest that the effect requires at least six weeks to six months of continued fasting.”
Neural Regulation of Sexual Behavior: Reduced Serotonin
To determine how fasting affected sexual behavior, researchers analyzed neurotransmitter levels in the mice’s brains. One finding stood out in mice with increased libido: serotonin levels were significantly lower.
“Serotonin is generally considered a brake on sexual behavior. In fasting mice, that brake was released,” Dr. Ehninger explained. “The mice became more sexually uninhibited.”
Serotonin is produced mainly in the gastrointestinal tract and also acts as an important neurotransmitter in the brain. Its production depends on tryptophan, an essential amino acid obtained through food. The study suggests that fasting reduced tryptophan intake, suppressing serotonin production and releasing the inhibitory control on sexual behavior.
Professor Zhou added: “Overall, fasting mice consumed about 15% fewer calories than controls, with a corresponding reduction in tryptophan. We still need to determine whether this neural mechanism is specific to 24-hour alternate-day fasting or also applies to other forms of calorie restriction.”
Potential Use for Low Sexual Desire in Humans
The findings offer new directions for basic science and potential clinical implications. Dr. Ehninger said: “Serotonin is also deeply involved in regulating human sexual desire. SSRI antidepressants relieve depression by increasing serotonin, but one side effect is reduced libido. Conversely, lowering serotonin might increase sexual desire.”
He noted that systematic research on fasting and human libido remains limited, but existing data and theory warrant attention. “Not everyone considers reduced libido a problem, but for some people, particularly middle-aged and older adults, it causes genuine distress. Medically, this is called hypoactive sexual desire disorder (HSDD). We hope fasting may eventually become part of a non-drug intervention.”
News | Study Finds 24-Hour Cyclic Fasting Increases Libido in Male Mice, Suggesting a New Approach to Low Sexual Desire
News | Study Finds 24-Hour Cyclic Fasting Increases Libido in Male Mice, Suggesting a New Approach to Low Sexual Desire
A recent study by the German Center for Neurodegenerative Diseases (DZNE), Qingdao University, and the University of Health and Rehabilitation Sciences found that regular 24-hour cyclic fasting significantly increased sexual drive in male mice, possibly by lowering serotonin levels. Published in Cell Metabolism, the study suggests that the mechanism may also apply to humans and could offer a new approach to reduced sexual desire.
Fertility Increased Unexpectedly in a Study Not Focused on Sex
The study initially examined how fasting affects offspring health, not sexual behavior. During the research, however, scientists noticed an unexpected result: older male mice that had fasted long-term produced far more offspring than expected.
Dr. Dan Ehninger, head of the DZNE research team and first author of the study, said: “These mice were equivalent to elderly humans. Their testicular function, sperm quality, and testosterone levels were no better, so their fertility should have declined. Instead, the opposite occurred.”
Further analysis showed that behavior, not physiology, was the key. Older fasting males mated much more often than same-age mice fed without restriction, and their increased sexual activity fully offset the physiological disadvantages of age.
Diet Pattern: Alternating 24-Hour Cycles
Beginning at two months of age, the male mice followed an alternate-day fasting pattern: unrestricted food for one day, then no food and only water the next. This cycle continued for 22 months. They had no contact with females until late in the study, when they were paired with three-month-old females that had never undergone dietary restriction.
Younger males that began fasting at two months and continued for six months also showed stronger sexual motivation than freely fed mice of the same age. Groups that fasted for only a few weeks showed no significant difference.
“This means the effect of fasting on sexual desire takes time to develop,” said Professor Zhou Yu, who led the Chinese research team. “Our data suggest that the effect requires at least six weeks to six months of continued fasting.”
Neural Regulation of Sexual Behavior: Reduced Serotonin
To determine how fasting affected sexual behavior, researchers analyzed neurotransmitter levels in the mice’s brains. One finding stood out in mice with increased libido: serotonin levels were significantly lower.
“Serotonin is generally considered a brake on sexual behavior. In fasting mice, that brake was released,” Dr. Ehninger explained. “The mice became more sexually uninhibited.”
Serotonin is produced mainly in the gastrointestinal tract and also acts as an important neurotransmitter in the brain. Its production depends on tryptophan, an essential amino acid obtained through food. The study suggests that fasting reduced tryptophan intake, suppressing serotonin production and releasing the inhibitory control on sexual behavior.
Professor Zhou added: “Overall, fasting mice consumed about 15% fewer calories than controls, with a corresponding reduction in tryptophan. We still need to determine whether this neural mechanism is specific to 24-hour alternate-day fasting or also applies to other forms of calorie restriction.”
Potential Use for Low Sexual Desire in Humans
The findings offer new directions for basic science and potential clinical implications. Dr. Ehninger said: “Serotonin is also deeply involved in regulating human sexual desire. SSRI antidepressants relieve depression by increasing serotonin, but one side effect is reduced libido. Conversely, lowering serotonin might increase sexual desire.”
He noted that systematic research on fasting and human libido remains limited, but existing data and theory warrant attention. “Not everyone considers reduced libido a problem, but for some people, particularly middle-aged and older adults, it causes genuine distress. Medically, this is called hypoactive sexual desire disorder (HSDD). We hope fasting may eventually become part of a non-drug intervention.”
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