Over 2,500 years ago, Hippocrates advocated the personalisation of nourishment and exercise as the safest way to health. He knew that our behaviours influence our health, but he did not know why. This book explains the missing link: the crucial role played by our hormones and what we can do to optimise them. Hormones set in motion the physiological processes that keep us alive, bringing our DNA to life by directing gene expression. Hormones are the protagonists in the interaction between lifestyle and health. We can harness our hormones positively to optimise health through our choice of behaviours. Conversely, mistiming between our actions and internal hormone biological clocks can derail the intricate interactions of hormone networks. For example, in relative energy deficiency in sport (RED-S). This book reveals the clandestine world of hormones, navigating the path to achieving full personal potential, through the different stages of life. This is relevant for both men and women, whatever your objectives, whether you are a high-level athlete; looking to improve health and fitness; seeking to understand hormone disruption; or meeting the challenges of physiological changes in hormones during life such as perimenopause and menopause. Practical tips and hormone stories provide actionable advice and real-life examples of how to tune in to your hormones and maintain hormone health. As the human lifespan extends, it becomes ever more desirable to remain healthy into old age. Understanding how and why your choice of lifestyle affects your hormones empowers you to take informed decisions to improve your personal health. A life-long, healthy mix of exercise, nutrition and sleep is open to anyone, at minimal cost.