Use your temperature minimum to time light, exercise, and meals

Your body temperature hits a daily low about 2 hours before your average wake time — knowing it lets you shift your clock deliberately.

Why it works

Core body temperature follows a circadian rhythm with a nadir roughly 90–120 minutes before habitual wake time. Light and exercise near the temperature minimum advance the circadian phase (shift it earlier), while the same inputs in the evening delay it. This phase-response curve is the mechanism behind jet-lag recovery and shift-work adaptation protocols.

How to do it

1. Estimate your temperature minimum by subtracting 90 minutes from your average natural wake time.
2. To shift earlier: get light and exercise just after your temperature minimum.
3. To shift later: delay light exposure and exercise to the evening.
4. Use meal timing in the same direction — eating earlier reinforces an earlier clock.

Evidence

The phase-response curve to light is well established in chronobiology: light before the temperature minimum advances the phase; light after delays it. This is foundational sleep medicine used in shift-work and jet-lag protocols. (clinical)

Translating lab circadian phase-shift findings into precise daily practice requires self-experimentation; individual chronotypes vary significantly.

Sources

• Czeisler et al. (1989), bright light resets the human circadian pacemaker, Science

Common mistake

Trying to become a morning person by setting an earlier alarm without shifting light, exercise, and meal timing — the alarm moves but the biology does not.