A kilojoule (kJ) is a unit of energy commonly used in nutrition and physics. It measures the amount of energy required to perform work or produce heat. One kilojoule is equal to 1,000 joules, which is the standard unit of energy in the International System of Units (SI). In nutrition, kilojoules help indicate the energy content of food. For example, a food label may show that a snack contains 500 kJ, meaning it provides that amount of energy when consumed. Understanding kilojoules can assist individuals in managing their energy intake for health and fitness goals.