Why do so many diets lead to more weight gain? Do more active people have faster metabolisms? Is exercise essential for weight loss? Over the past twenty years, evolutionary biologist Herman Pontzer has conducted ground-breaking studies across a range of settings, including pioneering fieldwork with Hadza hunter-gatherers in northern Tanzania. This book draws on his eye-opening research to show 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. By taking a closer look at what happens to the energy we consume, Pontzer 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, Burn will change the way you think about food, exercise and life.