A little-known scientific process is being hailed as the new way to lose weight, look younger and prolong life.
Autophagy is a natural regeneration process that occurs at a cellular level in the body, reducing the likelihood of contracting some diseases as well as prolonging lifespan.
In 2016, Japanese scientist Yoshinori Ohsumi won the Nobel Prize for his discoveries into the mechanisms of autophagy. These have led to a better understanding of diseases such as Parkinson's and dementia.
Since then, drug companies and academics have raced to find drugs that will stimulate the process, and diet and wellness experts are jumping on the bandwagon claiming that the process can be induced naturally by fasting, high-intensity exercise and restricting carbohydrates.
So what do scientists say?
"Certainly the evidence from experiments in mice suggest that would be the case," said Dr David Rubinsztein, professor of molecular neurogenetics at the University of Cambridge and UK Dementia Research Institute.
"There are studies where they have switched on the process using genetic tools or drugs or fasting, and in those cases the animals tend to live longer and be in better overall shape."
However, he said it was not yet clear how that translated to humans.
"For example, in mice, you see the effects of fasting on the brain in 24 hours, and in some areas of their body, like the liver, much more quickly. Yet even though we know fasting is beneficial, we don't know yet exactly how long humans would need to fast to see the benefits," said Dr Rubinsztein.
That said, fasting does stimulate autophagy, he said, and its benefits had also been proven by other studies.
What is autophagy?
- The word autophagy comes from the Greek for "self" and "phagein", which means "to eat"
- It is the process by which cells degrade and recycle their components
- It provides fuel for energy and building blocks for cell renewal
- After infection, autophagy can destroy bacteria and viruses
- Cells use autophagy to get rid of damaged proteins and organelles, to counteract the negative effects of ageing on the body.
Autophagy was first discovered in the 1960s, but its fundamental importance was only recognised after Yoshinori Ohsumi's research in the 1990s.
"What we've discovered is that it protects against diseases like Parkinson's, Huntington's and certain forms of dementia," said Dr Rubinsztein.
"It also seems to be beneficial in the context of infection control, as well as protecting against excessive inflammation."
New lifestyle books are saying the process can be "switched on" by changes to our diet and lifestyle, such as fasting – already popular with many of those who follow the 5:2 or Fast Diet.
One new book, Glow 15 by Naomi Whittel – a self-styled "wellness explorer" – sets out a 15-day programme that includes 16-hour fasts three times a week, reducing protein on some days, eating carbohydrates later in the day and periods of high-intensity exercise.
In basic tests of the programme on volunteers at Jacksonville University in Florida, she says she found a number of benefits.
"Some people lost weight, up to 7lbs in 15 days. Others saw a reduction in fine lines, changes in their blood pressure and improvements in lean muscle mass," she says.
Dr Rubinsztein says none of these lifestyle recommendations are going to do you any harm.
"And if you have a bad lifestyle, if you're always snacking and eating rubbish, then you wouldn't have the opportunity to switch this on," he says
Clearly, fasting to excess is not a good idea and anyone looking to make major changes to their diet or lifestyle should check with their GP first.
Dr Rubinsztein is optimistic about the future benefits of autophagy for treating disease.
His laboratory discovered that proteins form in clumps in the nerve cells of people with diseases like Alzheimer's and Parkinson's.
"We discovered that if you switch on autophagy you remove these proteins rapidly and protect against neurodegenerative diseases like Huntington's and forms of dementia."
He hopes that one day there might be drugs available to boost autophagy. Others clearly hope so too.
It was recently reported that a new start-up in America, Casma Therapeutics, received $58.5m to look into new drugs to boost autophagy.