Fasting for 25 hours on Yom Kippur is undeniably difficult. But there is one thing that can make everything easier:

Hydration.

Most people think the challenge of fasting is feeling “hungry.” In truth, avoiding thirst is much more important. The average person can survive for a month without food – but only three days without water.

With proper hydration, not only do you avoid the discomfort of thirst, but you also swallow more frequently, so your stomach does not feel as empty.

Fasting is easier if you prepare your body in advance. Here are Seven Simple Steps to maximize your hydration on Yom Kippur – leaving you with more strength and energy to do the truly important spiritual work of the day.

1) Start early.

The nausea and headaches that many people experience during a fast are often the result of caffeine withdrawal. Prepare yourself by reducing caffeine intake in the days leading up to Yom Kippur – and then stop caffeine altogether 24 hours before the fast. One trick is to brew mixtures of regular and decaffeinated coffee, increasing the proportion of decaf as you progress.

2) Pace yourself.

The morning before Yom Kippur, start with a large breakfast – based on cereals, breads and fruits. It will provide good energy during the day, yet these high-fiber foods will be far downstream by the time of the pre-fast meal when you’ll want a hearty appetite.

A large breakfast is also helpful because it stretches the stomach, preparing to receive more food and water later.

Eat a moderate lunch, early enough so that you will have an appetite for the final meal before the fast.

Start the final meal at least an hour before the fast begins, so there is no rush to eat quickly.

3) Avoid thirst-inducing foods.

One important way to remain well-hydrated is to avoid anything that will cause your body to get rid of water. Chocolate, tea, cola and coffee should be avoided, since caffeine has diuretic effects when consumed in large amounts (3+ cups daily). Alcohol is also a no-no, as it requires extra water to process through the system.

The other problematic food – salt – is well-known for causing thirst. Avoid salty foods such as pickles, cold cuts, cheese, canned fish, smoked fish and the Jewish comfort foods: chicken soup and brisket. Fresh fish and boiled chicken are good alternatives.

4) Carbs over protein.

Plan the menu of the final meal so that it emphasizes carbohydrates and low salt foods like pasta, potatoes, rice and bread (preferably brown rice and whole-wheat bread). These carbohydrates bond with water which your body can "drink" when it needs to during the fast.

Salads and other high-fiber foods should be minimized, since they travel quickly through the digestive system and provides little long-term satiation.

The final meal should include only small amounts of protein, which actually attracts and leaches water from your tissues. (Most of the dramatic weight loss that people experience on high-protein diets is lost water that protein molecules cannot hold onto or bring into your system – water that you want around during a fast.)

5) “Camel up.”

The key to an easy fast is to super-hydrate. Starting 24 hours before the fast, drink one cup of water every hour. (Set your PDA to remind you.)

Throughout the day, consume a lot of beverages. This will not fill you up, since liquids are absorbed quickly. Yet it will ensure that you’ve absorbed enough fluids during the day to start the pre-fast meal well hydrated.

Don’t drink syrupy beverages, which provide empty calories. Best bet: Pure H2O. Second best: diluted fruit juice.

Fruit, despite its high fiber content, is worthwhile since it carries a lot of water in a “time-release” form. Throughout the day, you can munch on water-rich foods like melon and grapes.

At the final meal, drink a few glasses, because many foods need extra water to be digested properly. For dessert, substitute sweets with watermelon or other water-retaining fresh fruit. Finally, drink a cup of warm water to put a smooth finish on your pre-fast prep.

6) Mental discipline.

A large part of successful fasting is in the mind.

Talking about your hunger will only focus your attention on food and make things more difficult. When you think about food, your body prepares itself metabolically to receive the food, causing the sensation of hunger.

The key here is to distract your mind from food. Fortunately, Yom Kippur provides plenty of opportunity to be involved in the important task of teshuva – spiritual self-improvement. The more you immerse yourself in prayer, the less you'll think about food.

One “kosher” way to “consume” during Yom Kippur is to smell spices. Cinnamon and cloves are a quick pick-me-up if you’re feeling weak, and can actually create a brain sensation of satisfaction.

Before smelling the spices, say the following blessing:

Saying a blessing over the spices also helps one to fulfill the special mitzvah to say 100 brachot each day.

7) Break the fast wisely.

Even those who have prepared well for the fast will be hungry afterward. Be sure not to eat too quickly at the post-fast meal. Begin with fruit or a glass of juice. These put sugar into the bloodstream and occupy space in the stomach, discouraging you from eating too rapidly.

Avoid pastries and sugary drinks, whose heavy glucose can shock the digestive system.

To prevent overeating, eat one portion and then take a break of a half-hour. Otherwise, the break-fast may turn into a weight-gain event (and a stomachache). Since the body protects itself from starvation when you are not eating by slowing down the rate at which it burns food, the calories you take on right after a fast will stay with you a lot longer than those acquired when your metabolism is functioning at full speed.

Have an easy and meaningful fast!

With thanks to Michael M. Segal, MD, PhD and Richard Israel