In much the same way as an engine runs on diesel fuel, the human body runs on:

• A. Oxygen
• B. Glucose
• C. Protein
• D. Fats

Answer: (B)

Energy for the body's cells comes primarily from glucose, the simple sugar you get from carbohydrates. Glucose is stored as glycogen in the liver and muscles and is quickly broken down to produce ATP, the energy currency the cells need to power everything from muscle contraction to brain activity. Oxygen helps these energy-producing reactions work efficiently, but it isn’t the fuel itself. Fats and proteins can be tapped for energy too, but they’re typically used when glucose supplies are limited or during longer, lower-intensity activity. Because of its rapid availability and central role in cellular energy, glucose is the best fit for what the body runs on.