Calories are the unit of measurement used to quantify the amount of energy food provides when consumed and metabolized by the body. Every time you eat, your body converts the macronutrients — carbohydrates, proteins, and fats — into energy, and this energy is expressed in calories. Specifically, carbohydrates and proteins each supply 4 calories per gram, while fats provide 9 calories per gram, and alcohol (though not essential) provides 7 calories per gram. The number of calories in a food item represents how much fuel your body can extract and use to support all functions, from basic processes like breathing and digestion to more intense activities like running or lifting weights. If you consume more calories than your body needs, the excess is stored as fat; if you consume fewer, your body will draw from stored energy to make up the difference. Understanding calories is essential for managing weight, energy levels, and overall health.