The amount of energy in food is typically measured in calories (cal) or kilocalories (kcal), with 1 kilocalorie equal to 1,000 calories. In scientific contexts, energy can also be measured in joules (J), where 1 kcal is approximately equal to 4,184 joules.
The energy content in food comes from macronutrients: carbohydrates, proteins, and fats, each providing different amounts of energy per gram:
- Carbohydrates: about 4 kcal (or 16.7 kJ) per gram.
- Proteins: about 4 kcal (or 16.7 kJ) per gram.
- Fats: about 9 kcal (or 37.7 kJ) per gram.
Understanding these measurements is important for assessing dietary intake and managing nutrition.