While people tend to follow new diets to get fit and reduce their weight, research has shown that in addition to weight loss, people who indulge in intermittent fasting may also have benefits like slow ageing, and be capable of fighting cancer as well as diabetes.
Intermittent fasting diets fall generally into two categories: daily time-restricted feeding, which narrows eating times to 6-8 hours per day, and so-called 5:2 intermittent fasting, in which people limit themselves to one moderate-sized meal two days each week.
“Intermittent fasting could be part of a healthy lifestyle,” said neuroscientist Mark Mattson, Professor of Neuroscience at the Johns Hopkins University School of Medicine, and who has studied the health impact of intermittent fasting for 25 years, and adopted it himself about 20 years ago.
In a review article published in the New England Journal of Medicine, Mattson said that an array of animal and some human studies have shown that alternating between times of fasting and eating supports cellular health, probably by triggering an age-old adaptation to periods of food scarcity called metabolic switching.
Such a switch occurs when cells use up their stores of rapidly accessible, sugar-based fuel, and begin converting fat into energy in a slower metabolic process.
Mattson noted that studies have shown that this switch improves blood sugar regulation, increases resistance to stress, and suppresses inflammation.
In the article, he said that four studies in both animals and people found intermittent fasting also decreased blood pressure, blood lipid levels and resting heart rates.
Evidence is also mounting that intermittent fasting can modify risk factors associated with obesity and diabetes, said Mattson.
Two studies at the University Hospital of South Manchester NHS Foundation Trust of 100 overweight women showed that those on the 5:2 intermittent fasting diet lost the same amount of weight as women who restricted calories, but did better on measures of insulin sensitivity and reduced belly fat than those in the calorie-reduction group.
Mattson added that preliminary studies have suggested that intermittent fasting could benefit brain health too.
A multicentre clinical trial at the University of Toronto in April found that 220 healthy, non-obese adults who maintained a calorie restricted diet for two years showed signs of improved memory in a battery of cognitive tests.
While far more research needs to be done to prove any effects of intermittent fasting on learning and memory, Mattson said if that proof is found, the fasting — or a pharmaceutical equivalent that mimics it — may offer interventions that can stave off neurodegeneration and dementia.
“We are at a transition point where we could soon consider adding information about intermittent fasting to medical school curricula alongside standard advice about healthy diets and exercise,” he said.
But, some experts argue that intermittent fasting may not be everyone’s cup of tea.
Mattson said that it may take some time for the body to adjust to intermittent fasting, and to get beyond initial hunger pangs and irritability that accompany it.
“Patients should be advised that feeling hungry and irritable is common initially and usually passes after two weeks to a month as the body and brain become accustomed to the new habit,” Mattson said.
To manage this hurdle, he suggests that physicians advise patients to gradually increase the duration and frequency of the fasting periods over the course of several months, instead of “going cold turkey”.