Your circadian rhythm is a roughly 24-hour biological cycle present in nearly all living organisms. In humans, the "master clock" is the suprachiasmatic nucleus (SCN) — a tiny region in the hypothalamus that coordinates the entire system by sensing light signals from the eyes.
What circadian rhythms regulate: • Sleep-wake cycle: promotes drowsiness at night and alertness during the day • Body temperature: lowest in the early morning (~36.2°C), peaking in the late afternoon (~37.0°C) • Hormone secretion: cortisol rises before waking; melatonin rises at night • Digestion and metabolism: meal timing affects how efficiently nutrients are absorbed and blood sugar is managed
Consequences of disruption: Shift work, jet lag, and chronic late-night schedules create "circadian misalignment." Research links chronic rhythm disruption with higher risk of obesity, type 2 diabetes, depression, and certain cancers. Even if sleep duration is adequate, sleeping at the wrong biological time reduces how restorative that sleep is.
How to protect your circadian rhythm: • Wake up at the same time every day — this is the single most powerful anchor for your body clock • Get 10–30 minutes of natural light in the morning to strengthen the daytime signal • Reduce bright and blue-spectrum light in the evening, especially 1–2 hours before bed • Keep consistent meal times — food intake is the second-most important "time cue" after light