People following 'Intermittent Fasting' or '5:2' diet have weakened immune systems, a new research shows.

Researchers at the University of Bath explain that the '5:2' diet has gained popularity lately. The diet has reached out to people mostly celebrities and the media endorsing and claiming its effectiveness in reducing blood pressure, increasing lifespan and protection against conditions such as dementia.

The diet recommends consuming 500 calories for two non-consecutive days in a week and one can have the recommended 2000 calories the rest of the days. For men it is 600 calories.

The team conducted the study on four stress and immunity genes in fruit flies. According to the researchers, these genes are similar to those present in humans.

Results of the study showed that fruit flies exposed to a fungal pathogen had longer lives. This was because the stress and immunity genes were activated after the exposure.

Researchers opine that treatments that increase the life expectancy are associated with weaker immunity and more susceptible to infection.

The study findings did not surprise the researchers.

"Many studies have documented benefits of diet restriction and anti-oxidants consumption, but there is a lack of data on levels of illness in people administered these anti-ageing treatments. We know that certain stresses such as starvation or exposure to pathogens can extend life and increase fertility, but we have found that ironically this has a trade-off in terms of immune function," said Dr Nick Priest, Lecturer in Biology & Biochemistry at the University, in a press release.

"There are clear health benefits to diets such as the 5:2 regime, but we need to bear in mind there are side effects. It shows that even the fountain of youth should come with a warning label," Professor Valter Longo said.

The study is published in the journal Evolution.