The Fasting Trick That Can Reset Your Body Clock

Struggling with jet lag or a completely wrecked sleep schedule? The solution might not be in a pill bottle—it could be in your refrigerator. Or rather, not in your refrigerator.

Scientists have discovered that your body runs on more than one internal clock. Beyond the well-known circadian rhythm that responds to light, you have a secondary timekeeper called the food-entrainable circadian oscillator—nicknamed the "food clock."

Your Brain's Backup Clock

This food clock exists for a very practical evolutionary reason. Our ancestors couldn't always eat when the sun was up. Sometimes food was only available at odd hours, and survival meant adapting quickly.

When you fast for an extended period (around 12-16 hours), your food clock becomes dominant. Your brain essentially says: "Forget what time the sun says it is—we need to be awake when food is available."

How to Use This to Your Advantage

Here's the practical application:

• Stop eating 12-16 hours before you want to wake up at your new time
• Sleep if you can during your normal rest period
• Eat breakfast at your desired new wake time
• Your body interprets this meal as "morning"

The research behind this comes from Harvard Medical School and Beth Israel Deaconess Medical Center. Scientists found that mice could shift their circadian rhythms by about 12 hours in a single cycle when food availability changed—far faster than light-based adjustment.

Not a Magic Bullet

Before you skip dinner expecting miracles, some caveats. This technique works best when combined with other circadian adjustments—light exposure, physical activity, and consistent sleep timing. It's one powerful tool, not the whole toolbox.

The fast needs to be significant enough that your body notices. A 12-hour overnight fast is pretty normal for most people, so pushing to 14-16 hours may be more effective for triggering the food clock response.

Best Uses

This approach is particularly useful for:

• Jet lag recovery when crossing multiple time zones
• Shift workers transitioning between day and night schedules
• Night owls trying to become morning people

The key insight is that your body is remarkably flexible. It wants to sync up with your environment—you just need to give it the right signals. For thousands of years, food availability was one of the most important environmental cues humans had. Your food clock is that ancient system, still running in the background, waiting to help you adapt.

So the next time you're dreading a red-eye flight or facing a brutal schedule change, consider letting hunger do some of the heavy lifting. Your stomach might just be the best alarm clock you have.