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Ask Dr. Denton: It's Lent. Can You Explain the Effects of Fasting?

Fasting is Spring Cleaning for the whole person, body, soul and spirit

Fasting gives us, body and soul, a spring cleaning.

Remember prayer time in the morning to set the right priorities. Start the day right and you will finish right.

Remember prayer time in the morning to set the right priorities. Start the day right and you will finish right.


By Dr. Denton D. Weiss
Catholic Online (
3/11/2024 (2 months ago)

Published in Lent / Easter

Keywords: Lent, Dr Denton Weiss, Fasting, Beautiful living,

PORTSMOUTH, VA. (Catholic Online) - Dear Dr Denton: As the Lenten season unfolds, can you tell me the effects of fasting on my body?

Recently, I awakened to a new Lenten season. Lent is truly my favorite spiritual time of the year. For me, it is a time of great joy. It cleanses my mind, body, and most importantly my soul. I have spent the past year building up toxins from the world I live in. Largely, it is the result of my own choices. I came off the holiday season and - presto, I was not quite as spry as I was in October when I was enjoying those little red rubies we call apples.

While Lent can be viewed as a season of sacrifice and doing without, I believe that it is the season of rebuilding and laying down a foundation that will help to direct our spiritual well being and perhaps our overall health.

What do I mean?

Prayer and fasting leads us to a deeper closeness to God and to peace and beauty within. Interestingly, fasting also gives our body a time to clean out the weight of a heavy year. Fasting on a purely physical level does have some significant and wonderful benefits.

Let's just start with calorie reduction. In the US, the American food factory produces enough food to fill every citizen with 3800 calories per day. By the way, we only need approximately 2000 calories per day to sustain a normal sized person.

So, how does fasting play a role in our health and wellness?

The most profound way is in the calorie restriction. Studies performed on animals and humans where caloric intake had been restricted have shown that it leads to increased longevity (a longer life). Please understand that I am NOT speaking of extreme fasting. The radical extreme fasts that are proclaimed to be the "cure all" for the body are far from the truth.

The problem is that caloric restriction data is often used as a means of promoting extreme diets and starvation type "de-toxing." "You should be able to smell the toxins coming off your body," is the common type of language used to promote an extreme diet or what is called a detoxifying fast.

The truth is that in the extreme detoxification diets and low calorie fad diets the body does give off an odor that is often reported to be the "toxins" coming off. In reality, when you drive your body into a starvation mode the body goes into ketosis. That is what has the somewhat sickly sweet smell. Not toxins, just ketosis.

In fasting, the body has a decreased calorie intake. The body needs those 2000 or so calories to stay at an even weight and function. When the calories are less than our daily needs we start breaking down our energy reserves - fat and muscle. In a short term fast such as a day of bread, honey, and water the body burns those fat stores.

In a diet where carbohydrates are limited for days to weeks, or absolute calorie reduction in the 1000 range, the body responds by burning both fat and muscles stores. In absolute starvation when the fat is gone, the body burns muscle.

That is why we see the horrible pictures of children with large bellies and thin limbs. The muscles of the abdominal wall - as well as the muscles on the limbs - have been used for calories. Muscle is made up of protein. When the muscle breaks down it forms ketones as a waste byproduct. In the ideal world, we fast enough to burn the excess fat stores. We also control our tendency to indulge our disordered appetites through focused prayer, meditation, exercise, and simple discipline.

How does fasting help the mind and body?

In the short term it is best understood through understanding the value of rest. The body needs rest to heal itself and to grow. During a day of fasting, the stomach and bowels are rested. The toxins that are produced by the body in the breakdown of food and the toxins in the food we eat are thereby limited. Remember those free radicals from my earlier articles? They are decreased because there are fewer being made as waste in your body. In addition, fewer are brought in with the foods we eat.

How does fasting help the brain?

Simply stated, the caloric rest has a mind clearing effect. As Americans, we often eat high carbohydrate, high calorie meals. Initially, with food intake, the brain gets a high calorie boost but as we begin to digest large amounts of food our blood flow is directed to the gut to help with nutrient breakdown and transport. Later, the insulin release is often higher than the caloric intake so the brain has a moment where the sugar in the blood is too low and we get tired and feel cloudy.

By fasting, the calories and carbohydrates we eat are limited. The body does not surge with too much insulin. Instead a small amount of calories are brought into the body so we can function and the remainder of our needs come from our own fat stores. The brain is rested because its needs are not in competition with the gut and the reduced insulin release allows the brain to get its supply of energy from balanced blood sugars.

A few simple recommendations:

Follow our Lenten calendar. Make Fridays, perhaps even Wednesday, your days to fast.

Start slowly - no meat. Then extend this to a low carbohydrate/ low fat day with water, a small piece of fish, honey on whole grain bread, a spinach salad with olive oil and a touch of vinegar.

Drink water over coffee, soda, or fruit drinks. If you need something else, or your caffeine headache is kicking in, the answer is tea. Try green tea as the primary choice followed by herbal teas or fruit teas such as lemon tea, hot apple spice or chamomile.

Remember prayer time in the morning to set the right priorities. Start the day right and you will finish right. A little walk in the evening or even midday will ward off those urges for sweets.

The truth is, fasting is extremely healthy for the body if the fast is not extreme. By that I mean not performed for days or weeks at a time.

But Dr D, there has to be more -----

Yes, there is more. The benefits of fasting are not just about the physical world, they are also about the spiritual world. Fasting is about becoming identified in solidarity with the poorest of the world in order to feel their hunger, their ache, their longing for sustenance. That is what compassion means. To enter into the suffering of another. It is for love - and for the beauty and dignity of the human person. In our small sacrifice we become one with each other and then we truly are one with Christ, one with God.

May we all fast together and then share our gifts as one.


Dr Denton D. Weiss, M.D. is board certified in both Plastic and Reconstructive Surgery and Otolaryngology-Head and Neck Surgery. Dr. Weiss' approach to his medical practice flows from his convictions about the meaning of life which are deeply rooted in his Catholic Faith. He and his wife, Michelle strive for an integrated approach to life which recognizes the unity of the body, mind and soul. They call this approach "Bella Vitae" or "Beautiful Living". He, and Michelle, are contributing writers to Catholic Online


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