CNN  — 

For the past year and a half, Keith Taylor and his wife have adopted a lifestyle that includes fasting on a regular basis. “For six days per week we don’t eat until around 5 pm, but eat as much as we want and whatever we want from 5 pm until we go to bed. It is not a diet in the classic sense – we do not restrict WHAT we eat or HOW MUCH we eat, but rather just WHEN we eat,” Taylor said in an email.

Since the Taylors have been intermittently fasting, often called just IF, they’ve maintained a healthy body weight, been more alert and energetic, experienced less stress, and are less prone to getting sick. While Taylor admits that whether or not he will live longer as a result of his eating pattern is a “good question,” but he feels optimistic.

“I already feel as though I am younger,” said Taylor. “And if I am showing objective signs of being younger – more vigor and positivity – then I think it is logical to assume that I have already lengthened my lifespan by moving to IF.”

Research on fasting

Research involving animals has revealed that intermittent fasting can reduce the risk of obesity and its related diseases, including non-alcoholic fatty liver disease, diabetes and cancer. According to Mark Mattson, chief of the Laboratory of Neurosciences at the National Institute on Aging, research from the 1980s revealed that the lifespan of rats increases substantially when they fast every other day, compared to rats who have food available at all times.

A much more recent study, published this month, found that mice who fasted, whether because they were fed all of their calories only once per day or because their calories were restricted, which naturally caused them to eat all of their limited food at once – were healthier and lived longer compared to mice who had constant access to food.

Trying to tease out whether fasting is simply a form of calorie restriction is very complicated, according to experts. But “in the absence of calorie restriction, and independent of diet composition, fasting mice do better than non-fasting,” explained Rafael deCabo, a scientist at the National Institute on Aging and the study’s lead author.

But do the health benefits of fasting, including the possibility of living a longer life, apply to humans?

So far, research has revealed promising results. One study published last year divided 100 people, all free of disease, into two groups. For three months, participants either ate whatever they wanted, or consumed between 800 and 1,100 calories for only five days out of the month – a pattern researchers refer to as a “fasting mimicking diet” or “FMD.” At the end of the study period, participants on the FMD who were at risk for disease saw their fasting glucose, an indicator of diabetes risk, return to normal. Markers for heart disease, along with high levels of cholesterol and triglycerides, decreased, as did levels of the 1GF1 marker of various cancers. Additionally, participants lost abdominal fat, while preserving lean muscle mass and metabolism, which is often sacrificed on a lower calorie diet.

A human trial on longevity is almost impossible to design, and would cost “a hundred million dollars or more,” according to Valter Longo, who co-authored the clinical study. “But if you look at the data from our trial … it would be hard to see how they would not live longer.”

“You think of diseases when you think of lifespan – like cardiovascular disease, cancer and diabetes – as major causes of death,” said Mattson. And if you have improvements in risk factors for disease, it does, “on average” promote lifespan, explained Mattson.

Longo, who also runs the Longevity Institute at the University of Southern California’s Leonard Davis School of Gerontology, adds that periodic fasting provides a “potential alternative to taking lots of drugs.”

And no major diet changes are necessary. “You can do this for five days, and then go back to what you would do normally,” added Longo.