What do you mean by calories in food?

Every time you sit down to enjoy a meal, each food item and beverage contains energy locked away in chemical bonds. Once the food or drink is ingested, it's metabolized or broken down by your body to release the stored energy. Your cells then capture and use this unleashed energy to fuel normal bodily functions necessary for survival. To measure the energy extracted and used from food and drinks, we use a unit called a calorie. In other words, a calorie is simply a standard unit for measuring energy. Here's a little scientific background you may be unaware of. The term "calorie" is technically defined as the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. However, the calories we use when we talk about the amount of energy in what we eat and drink are actually kilogram calories or kilocalories, a unit that equals 1,000 calories. The kcal is the most suitable unit of measurement for food and beverages because there is a large amount of energy stored in their molecules. After all, it is easier to say that one medium banana contains 105 kcal than 105,000 cal. But, in common, nonscientific usage, we use "calories" to mean "kilocalories." So, we say that banana has 105 calories. Nearly everything we consume has a calorie count, and those calories come from three energy sources—carbohydrates, proteins and fats.