Top Highlights

• Energy is the currency of life; without it, you’re dead. Your body is made up of roughly 37 trillion cells, each humming along like microscopic factories, every second of every day.
• Together, they burn enough energy every twenty-four hours to bring eight gallons (about thirty liters) of ice water to a raging boil.
• Nine-year-olds burn 2,000 calories; for adults, it’s closer to 3,000, depending on how much you weigh and how much fat you carry
• You breathe most of it out as carbon dioxide, and turn a small fraction of it into water (but not necessarily sweat).
• we’ve been taught to think of our bodies as simple engines: we take in “fuel” in the form of food, and burn it off by revving our engine with exercise. Any extra unburned fuel builds up as fat.