What is intermittent fasting?
Intermittent fasting means cycling between periods of eating and periods of not eating, for example eating only within an 8-hour window each day.
Think of it as giving a busy kitchen regular closing hours. When orders stop coming in, the staff can finally clean, repair the equipment and take out the trash instead of cooking nonstop.
Why it matters for aging
The most popular versions are time-restricted eating, such as 16:8 (eat within 8 hours, fast for 16), the 5:2 diet (two very low-calorie days a week) and alternate-day fasting.
It became popular because calorie restriction extends life in many animals, and fasting promised similar benefits without counting calories. For many people, a daily eating window is simply an easy way to eat a little less and avoid late-night snacking, which is a perfectly good reason to use it.
A common myth
Intermittent fasting burns fat and slows aging no matter how much you eat.
In human trials, its benefits mostly come from eating less overall. When calories were matched, a daily eating window didn't beat simple calorie cutting for weight or metabolic health.
Go deeper
Deep dives
- Does intermittent fasting slow aging? What the trials say
- How long do you have to fast for autophagy? The honest answer
- Does coffee break a fast? It depends what you're fasting for
Related terms
Updated Nov 9, 2026 · All terms