A measurement of heat, a Calorie is actually the amount of energy that will raise one kilogram of water 1° centigrade. Calories come from the food you eat.
Protein and carbohydrate foods have four calories per gram. Fat has nine calories per gram. Alcohol has seven calories per gram.
Fat is the most concentrated calorie source in the diet. If you are trying to lose weight, concentrate on limiting your fat intake and increasing the amount of fiber. High fiber foods have fewer calories PLUS they make you feel full.