Nutrition and Nutrients : Which nutrient provides 9 kcal per gram and serves as a secondary energy source?

Fats provide 9 kcal/g, more than double carbohydrates and proteins. They act as long-term energy storage, insulate body organs, and facilitate fat-soluble vitamin absorption (A, D, E, K). Essential fatty acids (linoleic, alpha-linolenic) must be obtained from diet; imbalance can affect inflammation and cardiovascular health.