Herman Pontzer's ground-breaking research has revealed how, contrary to received wisdom, exercise does not increase our metabolism. Instead, we burn calories within a very narrow range: nearly 3,000 calories per day, no matter our activity level. In this book, he draws on twenty years of cutting-edge science to take a closer look at what happens to the energy we consume. Burn explores the ways in which metabolism controls every aspect of our health—from fertility to immune function—and reveals the truth about the dynamic system that sustains us. Filled with facts and memorable anecdotes, this book will change the way you think about food, exercise and what really matters for your health.