Intermittent fasting is not a protocol you start on a Monday. Anytime you are not eating, you are intermittently fasting — which means you have been doing it your whole life without calling it that.
Dinner to breakfast the next morning is a fast of roughly 12 to 14 hours. Dinner to lunch the next day is about 16. Those are the same numbers that appear on every fasting chart, and most people hit the first one without trying.
How do you do intermittent fasting?
Treating fasting as a special intervention makes it feel like something you either succeed or fail at. Treating it as a window you already have makes it something you adjust. You can start and stop for any reason, or no reason at all.
The practical goal is to notice the window you are already keeping, then decide whether to narrow it.
Frequently asked questions
What is intermittent fasting?
Intermittent fasting is any stretch of time you are not eating. It is not a special program you start on a Monday. If you finish dinner and eat breakfast the next morning, you have already fasted roughly 12 to 14 hours. Most people have been doing it their whole life without calling it that.
Is it better to fast 12 or 16 hours?
Both numbers sit on every fasting chart, and you likely hit the first one already. Dinner to breakfast is about 12 to 14 hours; dinner to lunch the next day is about 16. Treat fasting as a window you adjust, not a test you pass or fail. Notice the window you keep now, then decide whether to narrow it.
What are the best hours for intermittent fasting?
The best hours are the ones you already keep. For most people that is the overnight stretch from dinner to breakfast, about 12 to 14 hours. Moving the first meal to lunch stretches it to about 16. You can start and stop for any reason, or no reason at all, so pick a window that fits your day.
Related reading
Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP
Interventional pain physician, addiction medicine specialist and obesity medicine diplomate.
Licensed in Missouri and Illinois.
Last reviewed September 20, 2026
