Kalorii

Kalorii, or calories, are units of energy used to quantify the energy contained in foods and beverages. In nutrition, the term calorie is often used interchangeably with the kilocalorie, the amount of energy needed to raise the temperature of 1 kilogram of water by 1 degree Celsius. In practice, food labels usually express energy in kilocalories (kcal); occasionally the term Calorie (with a capital C) is used to denote one kilocalorie. One kilocalorie equals 1000 small calories and equals about 4184 joules.

Energy content of foods is determined by analyzing macronutrients. The most common method is bomb calorimetry, which measures the heat produced when food is completely combusted. In dietary contexts energy values are commonly estimated using Atwater factors: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g. These values apply to metabolizable energy; actual energy absorbed can vary due to digestion and metabolism.

Calories play a central role in nutrition and weight management. Energy balance—the relation between energy intake from food and energy expenditure through basal metabolism and activity—helps explain weight gain or loss. Nutrient density and food quality matter because two foods with equal calorie counts can differ in vitamins, minerals, fiber, and other health effects. Guidelines for daily calorie intake vary by age, sex, weight, and activity level.

Historically, calorie concepts emerged in the late 19th and early 20th centuries, with Wilbur O. Atwater developing standard energy values and methods for nutrition research. Bomb calorimetry laid the groundwork for modern energy labeling, and the kilocalorie has remained a core unit in dietary guidelines and food labeling worldwide.