Certainly the way you treat your physical body will affect your mind. In magick you want an alert mind. Therefore, your body must be as healthy as you can keep it. Take care of your body. Exercise regularly. eat a good diet (with vitamin supplements), and do not consume anything which will have a negative effect upon the mind. Drugs, smoking, and alcohol should be restricted, or eliminated. (The mind can create any condition which a drug can create.) A good rule here is moderation in what and how much you consume. (Most of this stuff is pretty obvious isn't it.) You may also want to cut down on sugar and processed foods.
Many occultists advise dietary changes, especially the non-eating of meat. We cannot deny the physical, psychological, and spiritual effect which all foods have. This effect may be described as the 'heaviness' factor of foods. Various foods are so ranked in the chart, lighter to heavier:
1. lettuce and other greens.
2. fruits and most vegetables.
3. wheat, rice, and other grains.
4. nuts, beans, and other legumes.
5. cheese, dairy products, including eggs.
6. fish, seafood.
7. chicken, poultry.
8. beef, pork, other red meats.
Note that meats, especially red meats are the 'heaviest' foods. Generally, foods which are harder to digest, or which are higher in protein are 'heavier' than those which are not. Animal products are heavier than plants. Foods high in carbohydrate (candy, bread, starch) are heavy. However, the 'heaviness' of foods is not directly related to the amount of calories.
What this means is that for various reasons, the heaviness of food in your diet will affect your magical experiences. You may be able to increase your psychic receptivity ('energy level') by eating lighter foods, or by eating less. Conversely, emphasizing heavy foods in your diet, or eating larger helpings, may help to 'bring you down to earth' should you 'rend the veil' too much. These are generalizations, of course, and it may take a number of days of dietary change before you notice much effect. I do not advocate radical dietary changes, excessive fasting, or malnutrition. Your good health is far more important in magick than any temporary effect you get from prolonged starvation. A change in diet will sometimes only produce a temporary effect, until the physical body adapts to the change. Healthy natural foods and lifestyle make it easier for us to be healthy, but ultimately, good health is a mental quality (attitude).
~from Maat's Book of Shadows