If you feel tired, foggy, wired at night or flat during the day, the problem might not be willpower or sleep alone. It might be your body clock.

In Circadian, Professor Ian Hickie reveals the hidden 24-hour system that governs your mood, metabolism, immunity and mental sharpness. Drawing on three decades of clinical research as a global leader in circadian science, he shows how modern life - artificial light, erratic eating, shift work, chronic stress - pushes our internal clocks out of sync, leaving many of us feeling permanently jet-lagged.

Discover the four powerful circadian levers you can control:
- light exposure
- sleep timing
- eating patterns
- exercise timing

Morning light sets your master clock. Well-timed sleep restores brain and body. Eating in alignment with your metabolic rhythm helps protect against weight gain and diabetes. Exercise, especially in the morning and late afternoon, strengthens and stabilises the entire system.

This is not a sleep book. It is a blueprint for whole-body health. From depression and burnout to heart disease and cognitive decline, Hickie explains why timing underpins nearly every system in your body - and how small, consistent changes can transform the way you feel.

When your clock works, you work. Circadian shows you how to get back in sync - and stay there.