It’s one of Hollywood’s favourite diets, heralded by a legion of toned A-list fans including Jennifer Aniston and Mark Wahlberg.

Now, scientists say intermittent fasting could even help boost your sex drive — particularly older men.

Specifically, a group of German and Chinese researchers discovered the diet affected the concentration of serotonin — a hormone that can alter mood — in the brain. 

The tests on mice also showed the phenomenon was most effective among those had stuck to the diet for at least six weeks. 

Experts, today, who labelled the findings important, cautioned further research was first necessary to uncover whether the reduction in serotonin that boosted sex drive, would also occur with other types of fasting. 

Dr Dan Ehninger, research group leader at the German Center for Neurodegenerative Diseases (DZNE) and study lead author, said: ‘We realised it was a matter of behaviour. 

‘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. 

Jennifer Aniston , Chris Pratt and Kourtney Kardashian are among the Hollywood A-listers to have jumped on the trend since it shot to prominence in the early 2010s

A group of German and Chinese researchers discovered the diet affected the concentration of serotonin — a hormone that can alter mood — in the brain 

‘Their mating behavior more than compensated for the age-related physiological limitations.’ 

He added: ‘However, it is currently unclear whether the reduction in serotonin levels is linked to our specific feeding regimen or would also occur with other types of fasting. Future studies will need to clarify this.’ 

Despite swathes of studies suggesting intermittent fasting — which shot to prominence in the early 2010s — does work, experts remain divided over its effectiveness and the potential long term health impacts.

Some argue that fasters usually end up consuming a relatively large amount of food in one go, meaning they don’t cut back on their calories — a known way of beating the bulge. 

They even warn that it may raise the risk of strokes, heart attacks or early death. 

In the new study, one group of male mice undertook an intensive form of intermittent fasting from the age of two months, allowed to eat what they wanted for 24 hours, followed by 24 hours of water only.

The other group followed no dietary restrictions. Both were housed together without any contact with females.

They were then introduced to three-month-old females that had been raised without dietary restrictions. 

Despite swathes of studies suggesting intermittent fasting — which shot to prominence in the early 2010s — does work, experts remain divided over its effectiveness and the potential long term health impacts

The scientists found that among the sexually active male mice, serotonin was present at unusually low levels. 

Serotonin relies upon the amino acid tryptophan to be converted by the body.

But tryptophan can only be obtained through the diet or released via the breakdown of the body’s own protein stores, such as those found in muscle tissue. 

As such, when levels of tryptophan are low, less serotonin will be produced. 

Dr Ehninger said: ‘The lack of serotonin was clearly a result of fasting. 

‘These mice were, so to speak, sexually uninhibited, the usual regulatory restraint was diminished.’

Writing in the journal Cell Metabolism, the researchers also said a similar effect was observed among younger mice who had started intermittent fasting aged two months but had only followed the diet for six months before being introduced to females. 

They too, were more sexually active than mice of the same age who followed no dietary restrictions.  

However, the effect was absent in other groups – both young and old – that fasted for only a few weeks. 

Professor Yu Zhou, an expert in neurobiology at Qingdao University, added: ‘For intermittent fasting to increase sex drive, it takes some time.

‘Based on our experiments, the minimum duration appears to be somewhere between six weeks and six months.’ 

Dr Ehninger said: ‘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.’ 

The research also comes amid concern about a global sex crisis — or rather, lack of sex crisis.

One recent survey revealed more than a quarter (27 per cent) of Britons are now having less sex than they used to, with one in six admitting they haven’t got frisky the entire year.

According to a Royal College of Occupational Therapists poll of 2,000 adults last year, men and women typically have sex 46 times a year — once every eight days. 

But some have far less frequent amorous activity, with a tenth reported having sex less than once a year. 

Sex and intimacy have been linked to several health benefits, including improving the condition of your heart, reducing stress and even boosting mental health.