Eating in a 6-hour window and fasting for 18 hours can help you live longer

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(CNN) - Refraining from eating from 16 to 18 hours a day could be key to treating a variety of health conditions, even if you have to train to overcome hunger.

A review of previous studies in animals and humans in The New England Journal of Medicine suggests that intermittent fasting can reduce blood pressure, help lose weight and improve longevity.

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The report works as a kind of road map for doctors to prescribe fasting as a method of prevention or treatment for obesity, cancer, diabetes and heart disease.

The study's author, Mark Mattson, professor of Neuroscience at Johns Hopkins University, focuses on two types:
daily feeding with time restriction (eating 6-8 hours a day and fasting for 16-18 hours) and intermittent fasting 5: 2 (fasting two days a week, usually limiting a fasting day to 500 calories).

The problem? Most Americans do not fast intermittently (the norm is three meals a day plus snacks) and, therefore, doctors are less inclined to consider fasting as a solution to a wide range of health conditions, according to the report.

Because the research is relatively new, the report advises doctors to monitor their patients during intermittent fasting and gradually increase the duration and frequency of fasting to guide their transition.

How does it work

Intermittent fasting has been studied in rodents and overweight adults to improve health across the spectrum, although it is not clear whether those benefits are the result of weight loss.

Switching between fasting and eating can improve cellular health, Mattson said, most likely by triggering metabolic change. In metabolic change, cells use their fuel reserves and convert fat into energy, "changing a switch" from fat storage to fat saving.

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The benefits

The results on intermittent fasting vary in the effectiveness of the diet, but some studies in animals and humans have linked the practice to longer lives, healthier hearts and better cognition.

The article points to Okinawa residents, known for their extreme longevity and low-calorie and nutrient-rich diet. The authors stated that their intermittent fasting could contribute to their life expectancy and keep obesity at bay.

It is believed that intermittent fasting improves insulin resistance, which can stabilize blood sugar levels. The results of a small study of 2018 found that three men with type 2 diabetes, also known as onset diabetes in adults, were able to stop taking insulin after losing weight due to intermittent fasting, findings that clash with the widespread belief that Diabetes is incurable.

A previous study (co-authored Mattson) showed that change can increase resistance to stress by optimizing brain function and neuroplasticity, or the brain's ability to adapt and develop throughout life. And older adults who underwent a calorie-restricted diet showed better verbal memory compared to two other groups that had not fasted, according to a 2009 study.

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Physical function even improved for some patients. A study of young men who fasted every day for 16 hours lost fat and retained muscles while performing resistance exercises for two months.

Limitations

The long-term effects of intermittent fasting require more research that is not yet available, and the studies that exist are limited. Clinical trials focused on young, middle-aged and overweight adults, so the benefits and safety cannot be generalized to other groups, the authors said.

Another thing: it is a difficult diet to follow, particularly in the United States, where the concept of three meals a day is “so ingrained in our culture” that a change in the eating pattern often does not occur to doctors or patients wrote Mattson.

It will almost definitely leave participants hungry, irritable and less able to concentrate, the study said.

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Almost 40% of people who were assigned to a fasting diet dropped out of a 2017 JAMA study, which is one of the drawbacks of intermittent fasting as a weight loss regimen, said Dr. Frank Hu, president of the Nutrition Department from Harvard University, TH Chan School of Public Health, in statements to Harvard Health Publishing.

"Human nature is that people want to reward themselves after doing very hard work, such as exercising or fasting for a long period of time," he said. "Therefore, there is a danger of falling into unhealthy eating habits on days without fasting."

When the brain is deprived of food, the appetite hormones in the hypothalamus, the "hunger center" of the brain, are released in a burst and can cause overeating.

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But Mattson said the pain is temporary.

"Patients should be warned that the feeling of hunger and irritability is initially common and generally passes after two weeks to a month as the body and brain get used to the new habit," he said.

Intermittent fasting