All the food items we consume, can be divided into seven nutrients or scientifically named groups. These seven groups are - Carbohydrates, proteins, fats, vitamins, fibers, minerals and water. The body requires all these seven items for proper growth and development. Excess or deficiency of any of these nutrients can cause damage. Each has it's own use in body and should be consumed accordingly. To know the amount to be consumed, we have to know the functions of each nutrient. 

Proteins are the building blocks of the body i.e. it is the protein that form the bulk of muscles and nerve cells. It is also one of the basic component of cell walls.

Fats i.e. oil and cholesterols are also important component of the cell wall, nerve cells and brain. Any excess food eaten is converted to fats which is the storage form of the body. This stored fats lead to overweight problems.

Vitamins are the protective food items that protect eyes, brain, nerve cells and heart. Though required in small quantities, their inadequate intake lead to disease blindness, weak bones or degeneration of the brain. 

Fibers cannot be utilized by the body but are still important part of nutrients as they help in digestion and also prevent the absorption of the cholesterol. Fruits, vegetables and sprouts are very rich in fibers.

Water does not have any calories but is the most important component of our body. It helps in digestion, absorption, excretion of toxins, regulates body temperature  and most important carries oxygen to all the body parts.