Intermittent Fasting and Longevity: The Science Behind the Trend

Intermittent fasting is an eating plan that switches between fasting and eating on a regular schedule. There are studies and researches that shows that intermittent fasting is a way to manage your weight and prevent, or even reverse, some forms of disease.

While most diets focus on "what" you eat, intermittent fasting focuses on "when" you eat. This is the crucial difference, though here too, healthy eating is encouraged. However, with this diet, you only eat during a specific time. Research shows fasting for a certain number of hours each day or just eating one meal a couple days a week may have health benefits.

A 2022 study titled Intermittent and period fasting, longevity and disease, published in the Author Manuscript stated that cycles of fasting lasting from 12 to 72 hours followed by a refeeding period have beneficial effects of longevity, markers for health, stress, metabolic response, age-related diseases, and tissue regeneration.

Mark Mattson, a neuroscientist from John Hopkins, studied intermittent fasting for 25 years and he believes that "our bodies have evolved to be able to go without food for many hours, or even several days or longer. In prehistoric times, before humans learned to farm, they were hunters and gatherers who evolved to survive — and thrive — for long periods without eating. They had to: It took a lot of time and energy to hunt game and gather nuts and berries."

The official website of John Hopkins Medicine mentions that it was even easier to maintain a healthy weight in the US, some 50 years back, as there were no computers, TVs were turned off by 11pm, people stopped eating because they wanted to go to bed. Portions were also much smaller. More people worked and played outside, which also ensured getting enough exercise.

However, with TV, internet and other entertainment available 24/7, many are now staying up for longer hours, snacking all day long.

How does intermittent fasting really work?

It revolves around alternating periods of eating and fasting, giving your body a break from constant calorie intake. The approach can vary widely: you might restrict eating to an 8-hour window daily, leaving the remaining 16 hours for fasting, or eat only one meal on two specific days each week. The key is choosing a pattern that fits your lifestyle.

Here’s how it works: when you go several hours without food, your body exhausts its sugar stores and starts burning fat instead—a process called metabolic switching. Mattson explains, "Intermittent fasting contrasts with the typical eating patterns of most Americans, who consume food throughout their waking hours. When you eat three meals a day plus snacks without much exercise, your body primarily burns those calories, not stored fat."

By extending the fasting period, your body uses up stored calories and begins tapping into fat reserves for energy.

How to plan it?

Daily Time-Restricted Eating:

Limit eating to a six- to eight-hour window each day. A popular example is the 16/8 method, where you fast for 16 hours and eat during an eight-hour period.

5:2 Method:

Eat normally five days a week, and restrict your calorie intake to 500–600 on the remaining two days. For instance, you might choose Monday and Thursday as your low-calorie days.

Longer Fasts:

While fasting for 24–72 hours is possible, it’s not always advisable. Extended fasting can stress your body, potentially leading to fat storage rather than fat loss.