CALORIE. The calorie is a unit for measuring heat energy, and it is usually used as the unit for food energy and of energy expenditure. Media and lay attention to food, exercise, and health, as well as the greater prevalence of obesity during the past few decades, has resulted in a cultural preoccupation with caloric intake and expenditure in industrialized nations. Heat is that which produces a change in temperature. Heat was formerly regarded as a substance called "caloric," but it came to be viewed as the random motion of molecules.

The calorie has traditionally been defined as the amount of heat required to raise the temperature of 1 gram of water by 1.8°F (1.0°C), usually defined as from 58.1°F to 59.9°F (14.5°C to 15.5°C), under normal atmospheric conditions. Because electrical measurements can be standardized more accurately than heat measurements, a calorie is officially defined as equivalent to 4.186 joule. A...