Many dieting fads have come and gone in recent decades, but one technique that has persisted is intermittent fasting. But does it really work?
The Johns Hopkins Medicine neuroscientist Dr. Mark Mattson’s latest review article, “Effects of Intermittent Fasting on Health, Aging, and Disease,” which appeared in The New England Journal of Medicine on December 26, suggests that it can.
Mattson identifies two primary intermittent fasting diets: restricted eating periods, in which the individual consumes all his or her meals within a period of 6-8 hours a day; and 5:2 fasting, where a person only eats one moderate-sized meal two days per week.
Mattson studied the effects of intermittent fasting over a period of 25 years – including on himself.
Many studies have demonstrated that fasting aids cellular health. It is believed that this is due to an evolutionary adaptation to periods when food is scarce which has been termed “metabolic switching”: When the body’s cells use up all of the sugar-based nutrients, they start to consume the stored fat instead.
The average American today, who consumes three meals – and often more than that – daily, never undergoes this switch.
This is unfortunate, according to Mattson, as research has shown that metabolic switching lowers blood pressure, improves the body’s regulation of blood sugar, aids in its ability to deal with stress, decreases blood lipid levels, and suppresses inflammation.
Mattson also cites studies from the University Hospital of South Manchester NHS Foundation Trust which show that overweight women who adopted the 5:2 diet lost just as much weight as women who merely restricted calories but maintained their existing eating habits, and yet demonstrated better results in terms of insulin sensitivity and the reduction of belly fat.
Further, a recent multicenter clinical trial at the University of Toronto showed that dieting through calorie reduction alone led to better memory performance in subjects’ cognitive tests. While no studies have yet been done on the relationship between intermittent fasting and memory, Mattson believes that if it has the same effect as calorie reduction, it could help to prevent the onset of dementia and other brain diseases.
Mattson concedes that much research remains to be done on the effects of intermittent fasting. He also points out that many people are resistant to the practice, given that it takes the average human body some time to adjust and overcome the hunger pangs and irritability that initially occur, but that these symptoms usually pass within two to four weeks. The transition can be eased, he says, by gradually increasing the frequency and length of fasting over a period of months rather than trying to adapt to it all at once.