An element of a healthy lifestyle

The New Year is a time for many individuals to adopt new habits as a renewed commitment to their own health. Newly enthused fitness enthusiasts swarm gyms, and grocery stores are brimming with consumers eager to try new diets.

However, is there scientific evidence to support the claims made for these diets? Mark Mattson, Ph.D., a neuroscientist at Johns Hopkins Medicine, concludes that intermittent fasting does in a review article published in The New England Journal of Medicine on December 26.

Mattson, who has studied the health effects of intermittent fasting for twenty-five years and adopted it himself roughly twenty years ago, writes that "intermittent fasting may be part of a healthy lifestyle." Mattson, a professor of neuroscience at the Johns Hopkins University School of Medicine, explains that the purpose of his new article is to clarify the science and clinical applications of intermittent fasting in a way that may assist physicians in advising patients who wish to try it.

According to him, intermittent fasting diets generally fall into two categories: daily time-restricted feeding, which restricts eating to 6 to 8 hours per day, and so-called 5:2 intermittent fasting, in which individuals consume only one moderate-sized meal on two days per week.

Numerous animal and a few human studies have demonstrated that intermittent fasting and eating promotes cellular health, most likely by inducing metabolic switching, an ancient adaptation to food scarcity. This occurs when cells deplete their stores of readily available, sugar-based fuel and begin converting fat into energy via a slower metabolic pathway.

Studies, according to Mattson, indicate that this modification improves blood sugar regulation, increases stress resistance, and reduces inflammation. Due to the fact that the majority of Americans consume three meals plus snacks on a daily basis, they do not experience the switch or its purported advantages.

Mattson notes in his article that four animal and human studies found that intermittent fasting reduced blood pressure, blood lipid levels, and resting heart rates.

Increasing evidence suggests that intermittent fasting can alter obesity and diabetes-related risk factors, according to Mattson. Two studies involving 100 overweight women conducted at the University Hospital of South Manchester NHS Foundation Trust revealed that those on the 5:2 intermittent fasting diet lost the same amount of weight as those on a calorie-restricted diet, but performed better on measures of insulin sensitivity and had less abdominal fat than those on the calorie-restricted diet.

Recent preliminary studies, according to Mattson, indicate that intermittent fasting may also be beneficial for brain health. In April, a multicenter clinical trial conducted at the University of Toronto revealed that 220 healthy, nonobese adults who adhered to a calorie-restricted diet for two years displayed signs of enhanced memory on a battery of cognitive tests. While much more research is required to prove any effects of intermittent fasting on learning and memory, Mattson says that if such evidence is found, the fasting — or a pharmaceutical equivalent that mimics it — could be used to prevent neurodegeneration and dementia.

"We are at a crossroads where we may soon consider incorporating information about intermittent fasting into medical school curricula alongside conventional advice about healthy diets and exercise," he says.

Mattson admits that researchers "do not fully comprehend the specific mechanisms of metabolic switching" and that "some individuals are unable or unwilling to adhere" to the fasting regimens. However, he contends that most people can incorporate them into their lives with guidance and some patience. It takes time for the body to adjust to intermittent fasting and overcome initial hunger pangs and irritability. "Patients should be informed that initial feelings of hunger and irritability are common and typically subside after two to four weeks, as the body and brain adjust to the new routine," says Mattson.

Mattson suggests that physicians counsel patients to gradually increase the duration and frequency of fasting periods over a period of several months, as opposed to "going cold turkey." As with all lifestyle changes, according to Mattson, it is crucial for physicians to understand the science in order to communicate potential benefits, risks, and obstacles, as well as provide support.

The Intramural Research Program of the National Institute on Aging, National Institutes of Health, supported this research.