The yoga system of Patanjali is not a philosophical system. It is empirical. It is a tool to work with. But still, it has a philosophy. That too is just to give an intellectual understanding where you are moving, what you are seeking. The philosophy is arbitrary, utilitarian, just to give a comprehensive picture of the territory you are going to discover; but the philosophy has to be understood. The first thing about the philosophy of Patanjali. He divides human personality into five seeds, five bodies. He says you don’t have one body; you have layers upon layers of bodies, and they are five.
The first body he calls annamaya kosha — the food body, the earth body, which is made of earth and is constantly to be nourished by food. Food comes from the earth. If you stop taking food, your annamaya kosha will wither away. So one has to be very alert about what one is eating because that makes you and it will affect you in millions of ways because sooner or later your food is not just food. It becomes blood, your bones, your very marrow. It circulates in your being and goes on affecting you. So the purity of food creates a pure annamaya kosha, the pure food body. And if the first body is pure, light, not heavy, then it is easy to enter into the second body; otherwise, it will be difficult — you will be loaded. Have you watched when you have eaten too much and heavy foods? Immediately you start feeling a sort of sleep, a sort of lethargy. You would like to go to sleep; awareness immediately starts disappearing. When the first body is loaded it is difficult to create great awareness. Hence fasting became so important in all the religions. But fasting is a science and one should not fool around with it. – osho