The Nuance

Why Fasting Diets Are About to Get More Extreme

Two weeks without food? Some scientists think it could help.

Markham Heid
Published in
5 min readOct 11, 2018
Photo: oatintro/Getty

Every week, the Nuance will go beyond the basics, offering a deep and researched look at the latest science and expert insights on a buzzed-about health topic.

EEven if you’re unfamiliar with the nitty-gritty of intermittent fasting, you’re probably aware of its broad strokes. By restricting your food intake a couple days a week (the 5:2 diet) or squishing all your meals into a short daily window (time-restricted fasting), you can lose weight. There’s also mounting evidence that regular bouts of fasting can lower your disease risks, improve your brain function, and even extend your life.

Experts say these diets shift the body’s use of energy in ways that improve cell health.

After going about 12 hours without food, your liver’s stores of glycogen — a form of energy — are depleted, and your body taps into its fat cells for energy, says Mark Mattson, a senior investigator with the National Institutes of Health (NIH) who has researched fasting and its effects (and who practices time-restricted fasting himself). This shift places stress on your cells — mild at first, but more significant the longer you go without eating — that can trigger all sorts of beneficial adaptations.

Some scientists say longer fasts may one day prove to be superior to shorter ones for health and longevity. How long are we talking? Think two or even three weeks at a stretch, says Dr. Luigi Fontana, a professor of medicine and director of the Healthy Longevity Research and Clinical Program at the University of Sydney in Australia.

These interventions are extremely powerful, and they can work in your favor or against you depending on how you do them.”

Going that long without food may sound dangerous. (And if you just winged it, it would be.) But Fontana says doing this kind of extended fast once every five or 10 years — with medical supervision — may help the body clear out a lot of its “cellular garbage.”



Markham Heid

I’m a long-time contributor at TIME and other media orgs. I write mostly about health. I grew up in Michigan, but these days I live in southwest Germany.