What is the primary source of energy for the body?

• A. Protein
• B. Carbohydrate
• C. Fat
• D. Vitamins

Answer: (B)

Carbohydrates are the body's main energy source because they’re readily converted into glucose, the primary fuel used by most cells, especially the brain and active muscles. This quick supply supports immediate energy needs and helps maintain stable blood glucose during activity. Fat provides a larger energy reserve but is metabolized more slowly and is favored during longer, lower-intensity activity. Proteins are used mainly for building and repairing tissues and only contribute to energy when carbohydrate and fat stores are limited. Vitamins don’t supply energy themselves but serve as essential cofactors in metabolism. So carbohydrates best explain the body’s primary energy source.