Part 2/9:

Energy contained in food can be quantified as heat, measured in calories or kilocalories (kcal). When food is combusted with oxygen, it releases energy in the form of heat. Two primary definitions of calorie are widely recognized: the small calorie (cal), which refers to the energy needed to heat 1 gram of water by 1 degree Celsius (°C), and the large calorie (kcal), typically found on nutrition labels, signifying the energy required to raise the temperature of 1 kilogram of water by the same degree. One kilocalorie is equivalent to 1,000 small calories.