Dietary modifications will need to be made in certain stages of life. The main reason for this is that the metabolism changes with age throughout a lifetime. This causes people to burn fat at different rates at different stages throughout their lives. The metabolism is the chemical reactions that occur in every living organism to maintain life. The processes that occur, allow us to grow, reproduce, maintain our structure and respond to our environments. The metabolism of an organism decides which foods it will find nutritious and which it cannot eat. Some dietary changes that our bodies go through are simply to do with age. From birth we need milk to survive, and no solid food is needed at this stage. One of the reasons for this is that we have no teeth at birth, so we are not capable of chewing solid foods. Humans, as a species, are omnivorous, which means they can consume plant and animal materials. Once humans reach a certain age they will need to start eating solid foods to survive, as well as liquids. These solid foods can take on many forms and people eat these foods to produce energy. A human needs a certain amount of calories to have enough energy to survive on, and all foods have a calorific value, which determines how much energy they provide. Other reasons for dietary modifications may occur because of where a person lives and therefore they will eat what is available to them. Certain countries in the world have a large level of malnutrition, mainly because of lack of food, or the lack of a balanced diet. For the body to function correctly it needs to have a balanced intake of different food groups, including protein, fat, carbohydrate, sugar, salt and essential minerals and vitamins.
