Which nutrient class provides the highest energy density per gram?

Fats provide the highest energy density per gram compared to the other nutrient classes. Specifically, fats supply approximately 9 calories per gram, while carbohydrates and proteins provide about 4 calories per gram each. This significant difference in caloric content is due to the structure of fat molecules, which contain more carbon-hydrogen bonds than carbohydrates or proteins, making them richer in energy.

Vitamins, on the other hand, do not provide energy as they are classified as micronutrients. They play crucial roles in metabolic processes but do not contribute calories on their own. In the context of energy provision, focusing on the caloric value of macronutrients—fats, carbohydrates, and proteins—illustrates why fats stand out due to their high energy density, making them a crucial part of overall nutritional intake, especially for individuals needing dense sources of energy.