Study finds 24-hour fasting cycles enhance libido in male mice

Long-term fasting in 24-hour cycles increases the sex drive of male mice by lowering the concentration of the neurotransmitter serotonin in the brain. This effect is linked to a shortage-induced deficiency of the tryptophan of the precursor of the precursor-an amino acid that must be obtained by food. Researchers from Dzne report on this in the magazine Cell metabolismTogether with a Chinese team of Qingdao University and the University of Health and Rehabilitation Sciences. They suggest that similar mechanisms in people can exist and consider fasting as a possible approach to treating undesirable loss of sexual desire.

Fasting is a recurring topic of research because reduced food intake and therefore calorie limit has a variety of effects on the organism that goes beyond the generally observed weight loss. Dr. Dan Ehninger, research group leader at DZNE and the main author of the current study, and his team have also been working on this subject for quite some time.

“We are interested in the effects of fasting on aging. Use mice as a model we investigate the underlying biological mechanisms. Our goal is to gain insights that can also be relevant to people,” says the Bonn-based scientist.

More offspring than expected

The research results now published are based on a casual discovery, because Ehninger and his colleagues were originally on their way to investigating something else. Their goal was to investigate how fasting influences the offspring of male mice. A certain finding, however, sent their research in a new direction: old male mice – senior individuals according to human standards – who were recorded for a long time, produced an unusually large number of offspring. Unlike initial hypotheses, this phenomenon was not due to fasting effects on reproductive organs or the endocrine condition of the animals. Age -related changes in the testes, reduced sperm quality and lower testosterone levels, for example, argued against high fertility. “It was a bit of detective work to discover the real cause,” says Ehninger, whose research group collaborated on the current study with experts at Qingdao University and the University of Health and Rehabilitation Sciences led by Prof. Yu Zhou. “In the end we realized: it is a matter of behavior. The sober men had considerably more sexual contacts than mice that could eat freely. In other words, these animals had an unusually high frequency of couples and as a result an unusually high number of offspring for their age. Their coupling behavior more than compensated for the age of age.”

Fasting in a 24-hour rhythm

From two months old, these male mice were subjected to a specific form of intermittent fast. Their access to food followed a recurring 24-hour pattern: the animals were allowed to feed ad libitum for 24 hours, followed by 24 hours with access to water alone. During the fasting regime of 22 months, the men were brought together without any contact with women. They were later introduced in three months old females who had been picked up without dietary restrictions.

Effect takes time

Increased mating behavior was also observed in younger mice. These men also started intermittent fasting at the age of two months, but had only followed this diet for six months before they were introduced to women. They too were more sexually active than age -related peers who had received Ad Libitum. The effect, however, was absent in other experimental groups – both young and old – that only stuck for a few weeks.

“To increase intermittent fasting to increase the sex station, it takes some time,” says Zhou. “Based on our experiments, the minimum duration seems to be somewhere between six weeks and six months.”

A matter of serotonin

While investigating the causes, attention ultimately focused on neurotransmitters that influence sexual behavior. Some have a stimulating effect, while others act as inhibitors. Under the sexually active male mice, one factor stood out: serotonin – a chemical messenger that was usually associated with inhibiting effects – was present at unusually low levels.

In order to speak, these mice were sexually unrestrained, the usual legal restriction was reduced. “

Dr. Dan Ehninger, leader of research group at Dzne

Serotonin is mainly produced in the gastrointestinal tract, but also in the brain, where it acts as a neurotransmitter who mediates communication between neurons. However, its synthesis depends on the amino acid trptophan, which must be obtained by the diet or is released by the breakdown of the body’s own protein shops, such as the one in muscle tissue. Tryptophan is considered an essential amino acid, which means that neither mice nor people can synthesize it themselves. As a result, the intake of the diet plays a key role in regulating the tryptophaan levels in the body. In fact, it is found in many common foods. “The lack of serotonin was clearly a consequence of fasting,” explains the Dzne researcher.

Is the sober regime relevant?

“All in all, the down -to -earth mice consumed nearly fifteen percent fewer calories than the animals in the control group. This also applies to their intake of tryptophan,” says Zhou. “However, it is currently unclear whether the reduction of the serotonin levels is linked to our specific food regime or would also occur with other types of fasting. Future studies will have to clarify this.” As the scientist notes, it is also possible that the effect could occur under a general calorie restriction, where food is continuously available but in reduced quantities.

A possible approach for therapy

“Chemical messengers also play an important role in regulating sexual behavior in people. This applies in particular to serotonin,” says Ehninger. As he indicates, this is clear, for example, in the use of SSRIs, a class of antidepressants that increase serotonin levels. A possible side effect of this therapy is reduced libido. Conversely, it is known that lower serotonin levels promote sexual desire. “In view of this I find it very likely that sexual desire in people can be influenced by fasting – possibly not only in men, but also in women, because serotonin also influences their libido.” According to Ehninger, there are actually only a few scientific studies into the effects of fasting on human libido. “In my opinion, it would be logical to investigate this in more detail. I see potentially for therapeutic application. A lack of sexual desire is not necessarily considered problematic – but some people suffer from it. This condition is known as ‘hypoactive sexual desire disorder’ and influences particularly older adult options.