Fasting requires discipline, but if done the right way, dieters can lose weight, boost their brain health, and lengthen their lives. Researchers from the University of Southern California completed the third step of their fasting experiment by testing it on humans. Their results, published in the journal Cell Metabolism, may turn into the first safe and effective diet intervention, and could eventually be prescribed by doctors.

“Strict fasting is hard for people to stick to, and it can also be dangerous, so we developed a complex diet that triggers the same effects in the body,” said the study’s lead researcher Valter Longo, director of the USC Longevity Institute, in a press release. “I've personally tried both, and the fasting mimicking diet is a lot easier and also a lot safer.”

The human trial involved 19 participants and was designed to replicate Longo's yeast and mouse trials. Once a month for five days, participants limited their caloric intake by 34 to 54 percent — just low enough to mimic the effects of fasting. For the other 25 days of the month, participants returned to their normal eating habits.

After three months, Longo and his research team measured the participants’ biomarkers and found they were at a decreased risk of aging, diabetes, heart disease, and cancer. They’re calling it the "fasting mimic diet (FMD)," and it was shown to cut belly fat, improve learning and memory skills, and increase the number of stem cells ultimately leading to a longer lifespan.

It turns out that when there are a certain amount of proteins, carbohydrates, fats, and micronutrients, the body lowers the amount of hormone IGF-I it produces. Not only is this hormone responsible for promoting aging but it has also been linked to cancer susceptibility, which means less of it is better. Longo proved this theory before when he demonstrated how to starve cancer cells while protecting other cells from harm.

“It's about reprogramming the body so it enters a slower aging mode, but also rejuvenating it through stem cell-based regeneration,” Longo said. “Not everyone is healthy enough to fast for five days, and the health consequences can be severe for a few who do it improperly.”

Fasting can hurt the body if it's not done right. Women who try water-only diets, for example, put themselves at risk of developing gallstones if they aren’t properly supervised, Longo explained. Fasting isn’t for everyone, either. People with a body mass index below 18 — considered a normal weight — should not engage in fasting of any sort.

Diabetics also shouldn't partake in fasting or fasting mimic diets while they receive insulin or other drugs because the body uses up glucose energy supplies before it begins to burn fat. The process of burning fat to convert into fuel, also known as “ketosis,” makes the blood become more acidic, leading to bad breath, fatigue, and eventual kidney and liver damage. The FMD diet, however, is unique in that it allows the person to return to normal caloric intake for a majority of the month. Some fitness experts like Jillian Michaels, believe fasting can turn into an unhealthy “yo-yo” effect, and cause a person to cyclically fast and binge. The trick to avoiding the dreaded yo-yo effect is to not cut calories altogether but instead limit calories for one week a month, and gradually return to your normal caloric intake for the other three weeks.

The research team is set to meet with Food and Drug Administration officers soon, Longo said. They’ll work out the details on how to implement the diet safely in order to prevent and treat obesity. In the meantime, patients shouldn’t try it at home until Longo and his team finish testing through a randomized clinical trial, which will involve 70 patients over the span of six months.

“It's not a typical diet because it isn't something you need to stay on,” Longo said. "If the results remain as positive as the current ones, I believe this FMD will represent the first safe and effective intervention to promote positive changes associated with longevity and health span, which can be recommended by a physician.”

Source: Longo V. Cell Metabolism. 2015.