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• Posted January 31, 2024

New Clues to How Fasting Might Keep You Healthy

Many swear that trendy fasting diets are keeping them slimmer and healthier.

They may now have some science to back that up.

British researchers at the University of Cambridge believe they've uncovered the processes that cause fasting to lower bodily inflammation.

Long hours without eating appears to trigger a rise in a blood chemical called arachidonic acid, which has anti-inflammatory properties, reports a team led by Clare Bryant of Cambridge's department of medicine.

"We're very interested in trying to understand the causes of chronic inflammation in the context of many human diseases," she noted in a university news release.

The new findings were published Jan. 23 in the journal Cell Reports.

Bryant's team are focused on what scientists are now calling the "inflammasome" -- the cellular "alarm" system by which the body defends itself from injury or illness, triggering inflammation.

Inflammatory processes can go awry, however, helping to foster illness on their own.

"What's become apparent over recent years is that one inflammasome in particular -- the NLRP3 inflammasome -- is very important in a number of major diseases such as obesity and atherosclerosis, but also in diseases like Alzheimer's and Parkinson's disease, many of the diseases of older age people, particularly in the Western world," Bryant explained.

It's long been known that fasting appears to dampen inflammation, although it's not been known why.

In their research, Bryant's group analyzed blood samples from 21 people who ate 500-kilocalorie (kcal) meal, then fasted for 24 hours before consuming a second 500 kcal meal. 

They found that fasting upped blood levels of arachidonic acid, a blood lipid (fat). Levels receded again once a meal was eaten.

In lab experiments, Bryant's team found that arachidonic acid ratcheted down the activity of the NLRP3 inflammasome. That came as a surprise, since it had long been thought that arachidonic acid had the opposite effect on inflammation.

So, "this provides a potential explanation for how changing our diet -- in particular by fasting -- protects us from inflammation, especially the damaging form that underpins many diseases related to a Western high-calorie diet," Bryant said.

Could fasting help prevent or treat many diseases? That's tough to say, she said, because "the effects of arachidonic acid are only short-lived."

However, "our work adds to a growing amount of scientific literature that points to the health benefits of calorie restriction," Bryant said. " It suggests that regular fasting over a long period could help reduce the chronic inflammation we associate with these conditions. It's certainly an attractive idea."

Of course, the opposite could be true: Gorging on high-calorie food might boost inflammasome activity, promoting various diseases.

"There could be a yin-and-yang effect going on here, whereby too much of the wrong thing is increasing your inflammasome activity and too little is decreasing it,"Bryant explained. "Arachidonic acid could be one way in which this is happening."

More information

Find out more about fasting diets at the Mayo Clinic.

SOURCE: University of Cambridge, news release, Jan. 30, 2024