Shutdown and regeneration
Fasting has been performed by communities and cultures for millennia and Longo's team are curious about the advantages.
Their idea follows on from the long running trend of caloric restriction, mostly known through diets such as the 5-2 diet and intermittent fasting. Longo tested the impact of fasting for five consecutive days every month, believing that when the body thinks it's in a state of fasting, it shuts down and goes into standby mode.
"As cells are killed and the body goes into standby, your stem cells switch on," says Longo. Once switched on, the stem cells can regenerate the lost cells and organ mass -- leaving you shiny and new.
When cells in the body age, their ratios change and Longo believes the body's reaction -- and repair methods -- to fasting help restore them to when you were younger. "You're killing the bad cells and regenerating with cells that are more functional."
In a 2015 study, Longo's team set a specific diet for human volunteers, which mimicked the effects of fasting over five consecutive days monthly, for three months. Trials were also conducted in mice.
People consumed approximately 1000 calories on day one and 725 calories for the remaining four days, but these numbers alone didn't determine the benefit.
"It's not just about reducing calories", says Longo. His diet is designed to include specific percentages of protein, fat and carbohydrates, for maximum effect. The food items used, however, were specific to the trial and if translated to the public would involve designing meals made up of the right combination of nutrients.
"The human fasting mimicking diet (FMD) program is a plant based diet program designed to attain fasting-like effects while providing micronutrient nourishment (vitamins, minerals, etc.) and minimize the burden of fasting," Longo said in the study.
After three months, the benefits were a reduction in body weight as well as certain risk factors for cardiovascular disease. There was also an increase in certain stem cells in the body.
"The diet is turning on the body's ability to renew itself," says Longo.
The team have since calculated that following the diet every three months could provide enough of an impact as effects are thought to last up to six months.
How does it work?
"When you fast, you lower protein and certain amino acids and you control pathways [in the body]," says Longo. The pathways he refers to are known as TOR, PKA and IGF pathways, which when controlled can switch on certain reactions inside the body causing immune cells to die and organs to shrink.
This activation, or reduction, of pathways is why the components of the diet, such a proteins, must also be controlled. "You won't activate the correct pathways," says Longo.
"When you make IGF less active, it reduces risk factors linked to diabetes and cardiovascular disease," says Miguel Toribio-Mateas, Chairman of the British Association for Applied Nutrition and Nutritional Therapy.
According to Toribio-Mateas, the results confirm earlier theories that "some hormone-like growth factors that are required during development to grow, then become promoting agents of aging after development and sexual maturity have been reached". He also believes the benefits are down to improved efficiency on a cellular level.
"Cells have a list of things to do every day,...like getting rid of toxins" says Toribio-Mateas. If their workload is then disrupted by the need to store excess calories, certain products can accumulate. "Regulating calories can have a very positive effect," he says. To him, diet underpins longevity.
Is it safe?
Unlike the 5-2 diet, which requires two days of low calories at any point in the week, Longo's diet involves fasting for five consecutive days, which requires much more willpower.
"Five days is safe: going on for longer is difficult to do outside of a clinic," says Longo's
More work needs to be done to fine tune the diet and determine meals that meet the criteria. Longo has since founded his own nutrition company. L-Nutra, to sell products that serve this purpose, which may be seen as a conflict of interest. He states that profits are going back into funding further research by his team.
"The results of the study are encouraging and warrant more research in this area," says Toribio-Mateas.