When we say balance diet, it pertains to a variety of food types to be eaten that must belong to all food groups of nutrients such as carbohydrates, protein, fats, vitamins and minerals; but it also considers a balanced calorie intake that is recommended according to age, weight and height of a person. We are considering a food eaten in a daily basis.
The composition of the diet a person eats will vary according to age, body composition if more of fatty tissue or very muscular in built. It also varies when an individual has food restrictions due to food intolerance, food allergies, or a special health conditions such as a presence of diabetes.
Let's start in children; in this stage children still need to eat all of the complete nutrients daily, but protein must be in bulk in content in the food we feed them, as well as food rich in calcium. Hence protein as the body building food and the calcium for bone remodelling, then milk is an important food product that must be included daily aside from other food types to be served to ensure high nutrients required within this stage, because growth hormone is quite active in secreting in the body system, that at this point all necessary nutrients must be available in food the children must eat while actively growing.
As we become adult and in an old age, diet composition will be modified and much food type restricted. Most foods to be restricted are the sugary, fatty and salty foods. It cause a lot of ailment such as hypertension and diabetes that will affects body functioning specially the kidney and heart. Calorie must be well calculated in order not to lead in obesity. Food components will be more of fruits and vegetables, whole grains and fish are highly recommended, and drinking at least 8 glasses of water.
Remember, it is vital in the maintenance of all food nutrients present in food a person eats daily in all stages; but in terms of calorie, it must be strictly regulated in later age. Whatever too much can also poison the system.