Fasting doesn’t necessarily mean suffering. There’s quite a bit we can do to alleviate the bodily and mental stress that normally accompanies a fast. The day before the fast, follow the following guidelines:
1. Cut down your caffeine intake to minimize headaches. That means stop drinking coffee, tea, and cola at least eight hours before the fast, and preferably twenty-four hours before the fast.
2. Avoid salty, spicey, and fried foods on the day before the fast.
3. Avoid white sugar, white flour, and white rice. Eat whole-grained foods such as brown rice and whole-wheat bread or challa.
4. Drink a lot of water all day long.
5. Eat a good breakfast that includes fruits, veggies, eggs or sardines, and whole grains.
6. The pre-Yom Kippur meal (se'uda mafseket) should include baked or broiled fish, a veggy salad, consomme, a small portion of chicken or turkey, and a side dish of complex carbohydrates. Substitute sweet deserts with watermelon or other water-retaining fresh fruit, and a cup of herb tea with a whole-grain cookie.
On Yom Kippur:
7. The more you immerse yourself in prayer, the less you'll think about food.
8. Rest between prayers. Don’t run around outside, especially in the hot sun. Save your voice for prayers. Idle talking will make you thirstier, and will detract from the holiness of the day.
After the fast:
9. Drink two glasses of water, and then eat solids gradually, so as not to shock the digestive system. Begin with fruit, like plums or grapes. The worst thing people do is to consume pastries and soft drinks, or “lekach un bronfan” (cake and liquor) right after the fast (these are unhealthy anytime, all the more so right after the fast when they give your body a shock of glucose).
10. Forty-five minutes to an hour afterwards, one can eat a balanced meal with protein, carbohydrates, and vegetables. After eating, relax for an hour with your favorite book (preferably Gemara of the laws of Succoth from Shulchan Oruch) and your favorite beverage, then begin constructing your Succa.
Attention diabetics, heart patients, folks with high blood pressure, and people whose health depends on regular medication - you must be especially careful to ask your doctor if you are capable of fasting, and then consult with your local rabbi, giving him the doctor's exact opinion. For many such people, it is a mitzva not to fast on Yom Kippur.
The Israel Cancer Association recommends that cancer patients not fast without approval from their physicians. Fasting could cause considerable discomfort in cancer patients, who need a lot of liquids to alleviate side effects of chemotherapy. Again, first consult the doctor and then the rabbi. Give the rabbi all the details that you received from the doctor.
This past Tisha B'Av, I policed my synagogue looking for sick people who were fasting without authorization. It's no mitzva to get yourself rushed in an ambulance to the emergency ward because you were fasting without authorization.
Don't let children (boys under the age of 12 or girls under the age of 11) be overzealous. Make sure they eat on time.
With G-d's blessing and the above guidelines, you'll have an easy fast. May all of us be signed and sealed in the Book of Long and Happy Lives, amen.