Hungry for Health: Fasting's Medical Benefits

John Watson


July 12, 2018

In This Article

For most of us, a growling stomach is a siren song calling us to our refrigerator. However, for researchers and adherents of intermittent fasting (the practice of voluntarily abstaining from food and nonwater beverages), hunger is something not to vanquish but rather to embrace.

Fasting has been shown for years to be an effective nonpharmacologic strategy for counteracting some of the most entrenched modern ailments, from cardiovascular disease and cancer to diabetes and diminishing cognition.[1] The stumbling block was that this evidence was derived primarily from studies in rats and mice, which meant that intermittent fasting remained an interesting, but somewhat fringe, field of research. That has decidedly changed, though, with the recent publication of some small but promising investigations showing positive outcomes in humans.

"In the early 1990s, my own science colleagues viewed fasting as irrelevant, and it was largely ignored by the medical community," explained Valter Longo, PhD, a forerunner of fasting research and director of the Longevity Institute at the University of Southern California, Los Angeles. "Now things are changing very rapidly, and fasting is the most widely adopted diet in those under age 34 in the United States."

Fasting is the most widely adopted diet in those under age 34 in the United States.

Intermittent Fasting's Various Forms

"Intermittent fasting" is an admittedly vague umbrella term but one that is nonetheless useful for describing a wide variety of regimens.

The most popular fasting regimen is undoubtedly the 5:2 diet, in which participants restrict themselves to approximately 500-600 calories 2 days a week but eat as they normally would for the remaining 5 days. It comes garnished with all-important celebrity endorsements (for example, Jimmy Kimmel and Benedict Cumberbatch) and glossy coverage in magazines you would find at any grocery store checkout lane.

Other common regimens include time-restricted feeding (eat a standard amount of calories, but only within a limited time frame), alternate-day fasting (eating nothing one day, then whatever you like the next), and periodic fasting (abstaining from food and energy-containing beverages for continuous days, sometimes stretching out to 3 weeks). In addition, researchers such as Longo are investigating the efficacy of fasting-mimicking diets for reducing markers of aging and risks for age-related diseases.[2]

Because there have been no large randomized controlled trials comparing these regimens, we cannot yet establish superiority for any. Trends uncovered in clinical studies suggest some with greater potential though, according to Longo.

"I think the clinical evidence is strongest for the periodic fasting and fasting-mimicking diets used to treat specific problems, including obesity, high cholesterol, high blood pressure, inflammation (C-reactive protein), high triglycerides, and high fasting glucose/metabolic syndrome," he said. "The other major advantage of a periodic fasting or fasting-mimicking diet is that it only needs to be done for most people three to four times per year for 5 days."


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