caloric

Caloric is an adjective relating to calories, the units used to quantify energy in foods and drinks. In everyday nutrition, a calorie often refers to a kilocalorie (kcal); nutrition labels typically express energy in Calories, where 1 Calorie equals 1 kilocalorie (approximately 4.184 kJ).

Historically, the term and concept stem from early thermodynamics. The classical caloric theory proposed that heat was a material fluid called caloric. By the mid-19th century, experiments and the development of the mechanical theory of heat demonstrated that heat is a form of energy transfer, not a substance, and the kilocalorie remained as a practical unit for expressing the energy content of foods.

Measurement of energy in foods combines direct and indirect methods. Bomb calorimetry provides a direct measurement of energy released by combusting a sample. Nutrition science commonly uses Atwater factors to estimate usable energy: fat 9 kcal/g, carbohydrate 4 kcal/g, protein 4 kcal/g, and alcohol 7 kcal/g. Actual usable energy can vary due to digestion, absorption, and the presence of fiber or non-digestible components.

In diet and health contexts, caloric intake must align with energy expenditure to maintain, gain, or lose weight. Foods differ in caloric density, which is the number of calories per unit weight, affecting satiety and energy balance. The concept of calories remains central to nutrition science, dietary guidelines, and public health discussions on obesity and metabolic health.