Which macromolecule is primarily used for energy storage in the body?

Carbohydrates are primarily used for energy storage in the body due to their efficient conversion to glucose, which serves as a vital energy source for cells. When consumed, carbohydrates are broken down into simple sugars, and any excess is stored in the liver and muscle tissues as glycogen. Glycogen can then be quickly mobilized to meet the body's energy demands during physical activity or fasting periods.

Proteins, while essential for building and repairing tissues and for various metabolic functions, are not the body's primary energy storage macromolecule. Instead, the body resorts to proteins for energy primarily in situations of prolonged fasting or intense exercise when carbohydrate stores are depleted.

Vitamins are organic compounds essential for various bodily functions, but they do not serve as an energy source. They help in the metabolic processes but do not store energy themselves.

Nucleic acids, such as DNA and RNA, are critical for storing and transferring genetic information rather than serving as energy sources. Therefore, carbohydrates are the clear choice for energy storage, prominent for their quick availability and efficiency in energy utilization.