Everyone has heard of the saying “calories in and calories out” when referring to weight loss. This means that we must consume less calories or burn more calories than we take in in order to lose weight. But what are calories, why do we need them, and where do they come from? Calories are units of energy. The unit used for measuring foods is called a kilo calorie. It is the amount of heat  energy needed to raise the temperature of a liter of water 1 degree C. Calories are essential to our growth and development and for the repairs made to our tissues by the types of nutrients containing calories.  The energy or calories we eat all come from the sun. Plants store the energy as they grow and when we eat plants like fruit, vegetables and grains we obtain that energy for fuel our bodies use to function every day. When we consume animal meat it works the same way, the animals which have eaten plants containing compounds of energy from the sun store that energy within their tissues.

Now onto where calories in our meals come from. Calories in foods are measured in grams. There are 3 sources of calories in our diet. Carbohydrates yield 4 calories per gram, Protein also has 4 grams, and Fat contains 9 calories per gram. Alcohol, if consumed, also contributes calories (7 per gram) but is not considered a source of nutrients. Protein, fat and carbohydrates are energy yielding nutrients that all play essential roles in the structures of our bodies. I will talk more  in depth on nutrients and their roles in a future blog post.