Food should be for living and living should not be for food. Really it is food which determines your behavior, mentality strength and vigor. The elephant though having a huge body is very calm, physically having tremendous strength, vigor and vitality, very pleasant and always standing on four legs. But a lion with a comparatively smaller body is having an aggressive attitude and cannot be calm and quiet but is always roaring. It is the difference of the food they live on. The elephant is vegetarian, whereas the lion is a non-vegetarian.
What is true of beasts is also true of human beings. They can evaluate and discriminate the food. They should eat for physical, mental and intellectual growth.
Yogis discovered from their experience the best food to keep the full growth of man. The body needs many forms of nutrition like proteins, carbohydrates, minerals, vitamins, starch etc. food is divided into three categories Tamasic, Rajasic and Sattvic. Tamasic food includes heavy food, all food which is prepared the previous day and so on. Rajasic food includes meat and all the spices, chilies and so on. Sattvic food is such as grain, dairy products, vegetables, fruits, nuts, honey and nutritive roots. For good health, concentration of mind, control of emotions and sharp intellect sattvic food is recommended.

Selection of Food for Yogic Diet

Grains including wheat, rice, dhal, maize, ragi etc – 30% 
Dairy products – 20% 
Vegetables – 20%: 

Yogis say that there are five vegetables which are the best and five herbs. 
The vegetables are; Ladies finger, brinjal, bitter gourd, parval and all leafy vegetables. 
Brinjal for winter and bitter gourd for rainy season. Ladies finger is good for all season. 
There are many other vegetables which can be used now and then, not every day. 
Such as green beans, snake-gourd, tomato, carrot, beet root, drum-stick, cauliflower, cabbage, potatoes. 
Some of the greens of these vegetables are good. A little carrot can be used every day.
Fruits and Honey – 20%: 
Honey is the best sweetening. Jiggery or brown sugar also can be used. 
White sugar is completely forbidden because it contains a lot of starch. Every fruit is good. 
It should not be too ripe or too raw. Apple is the best fruit. Dried fruit is not a yogic food because it is hard to digest.
Nuts – 10%: 
Coconut is the best. Cashew nut and groundnut can be taken a little. 
Mustard, Jeera(Cumin seed), Salt, Curry tree or sweet neemleaf, Cardamom, Jaggery and Oil can be used to make food wholesome, tasty and pleasant. 
These should not be too much but very moderate. 
Onion and Garlic must be avoided as much as possible. 
Any alcohol or thing which gives slightest stimulation to the body, even tea and coffee should be avoided.

Attitude Towards Eating

The most important thing about food is not the food itself but how you eat it. 
If a preson eats food when excited, that will not help him at all. 
It may even be harmful. 
Angry, disturbed or excited feeling will do harm. 
The person eating the food must be clam, quiet, undisturbed and undistracted. 
The mind too should think of the eating process. 
In the old Hindu household food is not served till you change your dress, wash your hands and feet, sit at a particular place, take water after the food is laid down, sprinkle water round it after the mantras and then only eat it without distractions. Even the mantras work as auto-suggestion and food becomes not only tasty but healthy. Even the poison given to saint Mirabai did not harm her because of auto-suggestion.

Food should be broken into pieces by teeth, mixed with saliva and swallowed. 
The juices which the tongue produces are extremely helpful in digestion. 
Therefore you should chew slowly and then swallow.
While taking in food no one should drink water. 
That will dilute the juices and reduce their capacity to help indigestion. 
Water should be taken half an hour after and as much as one wants.
One cannot prescribe the quantity food to be taken, since men are not alike in size. 
The Yogis have discovered a technique in eating. 
Half the stomach should be filled with food; of the remaining space half is for water and the rest for gases, which are caused by the fermentation of food. 
If there is no space for gases they will press against the heart and choke it. 
If these cautions are not heeded people will feel uneasy after a heavy meal and there are instances of heart attack after taking food.
After taking food there should be a gap of three to four hours as that much of time is reqired for the digestion. 
If anything is eaten in between  then digestion becomes difficult. 
If this happens repeatedly then the power of digestion is impaired and troubles start. 
After all the stomach is a sensitive part of the body. 
Proper food at the proper time keeps the stomach in an excellent condition. 
It follows thus that there will not be any diseases. 
This is the road to happiness. ;)