National Academy of Sports Medicine (NASM) Certified Personal Trainer (CPT) Practice Exam

Which sugar is considered the body's main source of fuel, being manufactured from carbs, fats, and occasionally proteins?

1. Fructose

2. Glucose

3. Lactose

4. Sucrose

The correct answer is: Glucose

Glucose is recognized as the body's primary source of energy. It plays a vital role in cellular metabolism, as it is the main carbohydrate that the body utilizes for immediate energy. When carbohydrates are consumed, they are broken down into glucose, which can then enter the bloodstream and be used by cells for energy production. Additionally, under certain conditions, fats and, to a lesser extent, proteins can also be converted into glucose through processes such as gluconeogenesis, ensuring that the body has a readily available energy source even when carbohydrates are scarce. Fructose, although a sugar, does not serve as the main energy source for the body in the same way glucose does. Lactose and sucrose are also types of sugars, but they are not utilized as the body’s chief energy source. Lactose is primarily found in dairy products, while sucrose is common table sugar made from glucose and fructose bonded together, and both require processing before they can provide energy. Thus, glucose distinctly stands out as the principal fuel that the body efficiently uses for energy.