The Health Benefits of Fasting

SerendipUpdate's picture

Biology 103
2002 First Paper
On Serendip

The Health Benefits of Fasting

Will Carroll

There has been much contention in the scientific field about whether or not fasting is beneficial to one's health. Fasting is an integral part of many of the major religions including Islam, Judaism and Christianity. Many are dubious as to whether the physiological effects are as beneficial as the spiritual promoted by these religions. There is a significant community of alternative healers who believe that fasting can do wonders for the human body. This paper will look at the arguments presented by these healers in an attempt to raise awareness of the possible physiological benefits that may result from fasting.

Fasting technically commences within the first twelve to twenty-four hours of the fast. A fast does not chemically begin until the carbohydrate stores in the body begin to be used as an energy source. The fast will continue as long as fat and carbohydrate stores are used for energy, as opposed to protein stores. Once protein stores begin to be depleted for energy (resulting in loss of muscle mass) a person is technically starving. (1)

The benefits of fasting must be preceded by a look at the body's progression when deprived of food. Due to the lack of incoming energy, the body must turn to its own resources, a function called autolysis. (2) Autolysis is the breaking down of fat stores in the body in order to produce energy. The liver is in charge of converting the fats into a chemical called a ketone body, "the metabolic substances acetoacetic acid and beta-hydroxybutyric acid" (3), and then distributing these bodies throughout the body via the blood stream. "When this fat utilization occurs, free fatty acids are released into the blood stream and are used by the liver for energy." (3) The less one eats, the more the body turns to these stored fats and creates these ketone bodies, the accumulation of which is referred to as ketosis. (4)

Detoxification is the foremost argument presented by advocates of fasting. "Detoxification is a normal body process of eliminating or neutralizing toxins through the colon, liver, kidneys, lungs, lymph glands, and skin." (5). This process is precipitated by fasting because when food is no longer entering the body, the body turns to fat reserves for energy. "Human fat is valued at 3,500 calories per pound," a number that would lead one to believe that surviving on one pound of fat every day would provide a body with enough energy to function normally. (2) These fat reserves were created when excess glucose and carbohydrates were not used for energy or growth, not excreted, and therefore converted into fat. When the fat reserves are used for energy during a fast, it releases the chemicals from the fatty acids into the system which are then eliminated through the aforementioned organs. Chemicals not found in food but absorbed from one's environment, such as DDT, are also stored in fat reserves that may be released during a fast. One fasting advocate tested his own urine, feces and sweat during an extended fast and found traces of DDT in each. (5)

A second prescribed benefit of fasting is the healing process that begins in the body during a fast. During a fast energy is diverted away from the digestive system due to its lack of use and towards the metabolism and immune system. (6) The healing process during a fast is precipitated by the body's search for energy sources. Abnormal growths within the body, tumors and the like, do not have the full support of the body's supplies and therefore are more susceptible to autolysis. Furthermore, "production of protein for replacement of damaged cells (protein synthesis) occurs more efficiently because fewer 'mistakes' are made by the DNA/RNA genetic controls which govern this process." A higher efficiency in protein synthesis results in healthier cells, tissues and organs. (7) This is one reason that animals stop eating when they are wounded, and why humans lose hunger during influenza. Hunger has been proven absent in illnesses such as gastritis, tonsillitis and colds. (2) Therefore, when one is fasting, the person is consciously diverting energy from the digestive system to the immune system.

In addition, there is a reduction in core body temperature. This is a direct result of the slower metabolic rate and general bodily functions. Following a drop in blood sugar level and using the reserves of glucose found in liver glycogen, the basal metabolic rate (BMR) is reduced in order to conserve as much energy within the body as can be provided. (2) Growth hormones are also released during a fast, due to the greater efficiency in hormone production. (7)

Finally, the most scientifically proven advantage to fasting is the feeling of rejuvenation and extended life expectancy. Part of this phenomenon is caused by a number of the benefits mentioned above. A slower metabolic rate, more efficient protein production, an improved immune system, and the increased production of hormones contributes to this long-term benefit of fasting. In addition to the Human Growth Hormone that is released more frequently during a fast, an anti-aging hormone is also produced more efficiently. (7) "The only reliable way to extend the lifespan of a mammal is under-nutrition without malnutrition." (5) A study was performed on earthworms that demonstrated the extension of life due to fasting. The experiment was performed in the 1930s by isolating one worm and putting it on a cycle of fasting and feeding. The isolated worm outlasted its relatives by 19 generations, while still maintaining its youthful physiological traits. The worm was able to survive on its own tissue for months. Once the size of the worm began to decrease, the scientists would resume feeding it at which point it showed great vigor and energy. "The life-span extension of these worms was the equivalent of keeping a man alive for 600 to 700 years." (8)

In conclusion, it seems that there are many reasons to consider fasting as a benefit to one's health. The body rids itself of the toxins that have built up in our fat stores throughout the years. The body heals itself, repairs all the damaged organs during a fast. And finally there is good evidence to show that regulated fasting contributes to longer life. However, many doctors warn against fasting for extended periods of time without supervision. There are still many doctors today who deny all of these points and claim that fasting is detrimental to one's health and have evidence to back their statements. The idea of depriving a body of what society has come to view as so essential to our survival in order to heal continues to be a topic of controversy.



1)"Dr. Sniadach – True Health Freedom 3


3)"Ketosis by Sue Reith"

4)"Nutriquest, March 11th, 2000 – Ketosis and Low Carbohydrate Diets"

5)"WebMD – Detox Diets: Cleansing the Body"


7)"Fasting – Good Morning Doctor"

8)"The health Benefits of Fasting"



Comments made prior to 2007

Great essay. Do you have one good referrence on how to stage a fast? I am looking for a safe way to stage a fast in my home. Does it require special teas or anything outside of water? ... Elie, 30 September 2005



The term for the breaking down of fat is lipolysis, not autolysis. Autolysis is the self-destruction of cells ... Paul, 3 April 2007


Anonymous's picture

first time fasting

Hello, I have only fasted for 3 days with water & tea. I am amazed at the toxins that came out. Likewise, I was also a smoker. Not now. I would love to go on a longer fast. This is my first time to ever fast. I too lost some weight, but not a lot. I'm small anyway & my main concern was getting the toxins out. My trouble was - feeling weak, sometimes feeling shaky, upper stomach pains, & now burning in urine. I went off my fast & ate - ate quite a bit actually - however -- all good foods. But I am going back on the fast. My concern is hurting kidneys, etc, by doing so that soon. I am curious if this is normal. And would love any advice or personal experiences to be known. Many thanks in advance. I plan to restart the fast again tomorrow. I also highly recommend it for all kinds of reasons. Esp.. with getting off sugar caffeine & quitting smoking. It's nice to feel clean, but I do know it takes more than 3 days - more than 1 or 2 weeks of water fasting in order to be completely cleaned. And my diet from now on will be -- mostly vegan.

RE's picture

On day 7 of a water fast

I have attempted fasting before with only water but only made it to day 4 at which point I began to feel dizzy and so I began eating again. Even so the fast proved useful and I retained a diet of mainly vegetables raw, and water or tea which resulted in more energy and huge weight loss. I do worry about people trying this and going for a while and gaining more weight back after resuming normal eating. Being on day 7 I am having trouble keeping my stomach from hurting (especially during any type of activity or even getting up) and so I am wondering what the issue could be here. I do feel fine otherwise and am hopeful it will pass soon as I intend to go 25 days or so. I know now that you must resume eating very slowly after a long water only fast and I do agree that there are many health benefits although I do not instantly support most types of holistic or natural medicines because of the many false claims out there.
Any input would be nice

chad's picture

on day 7 of water fast

I am also on day 7 of a water fast. My stomach also hurts. A different kind of pain than I have ever felt before. I am assuming it has to do with my body eating away at my fat. But I really do not know. I am going for a 14-21 day fast or when ever real hunger returns to me. I am glad to see someone with the same symptom as myself.

Katrina's picture

Good!! Okay, I was fasting

Good!! Okay, I was fasting last week and made it to day 5 and I didn't think i could even get out of bed. I managed to make it thru the day, but my stomach hurt alot as well, as soon as i ate something all the pain went away. I was worried as to what the pain was so i continued with my normal diet. I too want to clean all the toxins out of my body and try to work my way back into eating with healthy wholesome foods. Today I started again with my fast, now that I know i was not the only one with the strange stomach ache, I hopefully can make it past it when it creeps up onme soon and contiue with my 21-day fast. And other helpful tips anyone has would be great.

Leah Webster's picture

fasting in stages- fasting buddy

I am 28 years old, and am new at fasting. My goal of fasting is both physical and spiritual refocusing. So far the Lord has truely opened great verses and understanding. Without Him I could not last a day.
I have been focusing on my health since 10/20/08. Well, 10 days. Starting weight 251 lbs. First 5 days fruits and veggies then I started my juice fast. My plan is to fast in stages building up to a 40 day fast. I want to connect with the father in a new and deeper level. 3,7,14,21, 30, 40 day fasts with 7 days partial fasting inbetween. The first 3 days of the fast went good, I was moderately hungery. Day 4 I fasted all day then had 4 Tsp of vanilla yogart and 1Tbl chicken liver around dinner time. Day 5 I fasted all day then had 1/4 cup green salad w/ lemon juice at dinner time. This has really helpped clean the bowels.

I weighted in at 236lbs this morning. That is the loss of 15 lbs in this 10 day time frame.

Fasting is greatly worth it and I will continue the plan.
It is good to hear I am not the only person who has had some considerable discomforts. To be honest enought to stand out. I look forward to continuing on this fasting journey and would like to find a fasting buddy.

On 11/08/08 I will be starting the 7 dat juice fast if anyone is interested in joining me feel free to email me

Anonymous's picture


I started a fast today and have done a few over the years and read today in Is 58 about the fast that God chooses- very good. I'm also doing it for health benifits and to become closer to the lord- My goal is 5 day water fast and I'll see beyound that if I will go further- how is your fast going! God bless you!
Jer. 20.11

Anonymous's picture

this is the best reason to

this is the best reason to fast to get closer to the fasting we humble our selves before the lord

Bennet's picture

16 years old and wanting to fast for a short time

I'm 16 years old and a male i don't know if that matters though. I'm wondering is it safe for me to go on a water fast being 16? I'm thinking of going on just a 1 to 2 day fast right now. and i would like to know what foods should i eat after the fast. If its just a 1 to 2 day water fast would it matter what foods i eat after the fast?

Steve H's picture

When I was 16 I fasted 36

When I was 16 I fasted 36 hrs every week for quite awhile , I did a seven day water fast and 21 days on grapes at different times.It total matters what you put in your face after a fast. Raw veggies are a great place to start and with fruit to follow . Depends what condition you are in before you start, read and get informed first

James's picture

Toxic Concern?

I am 24 6'2" 225 lbs and probably borderline alcoholic because I hang out at bars with my friends like 3 or 4x a week. I smoke cigs and occasionly pot. My diet is 90 percent meat/cheese/bread. My body has just recently shown me a few reasons why this road leads to destruction. I want to fast then adobt a somewhat vegan diet so I can enjoy sports and health for many years of my life. Will a fast release too many toxins into my bloodstream at the same time? I am sure I am a toxic wasteland inside. What type of fast and how long do you think I should go for one?

Anonymous's picture

I think you are to toxic to

I think you are to toxic to go on water fast, try going on vegetable juice fast ,get yourself a juicer and juice carrots lemons tomatoes celery ect.Ive done this type fast and have had excellent results

Nin's picture


You should probably take a week of a raw-vegetable/fruit diet or a vegan diet, with some nutritional supplements(If you don't ease into it with some vegetables/fruit first, you'll feel like hell). A water fast can be dangerous if you are missing any nutrients, as many Americans are for Potassium. Go to a doctor and measure the nutrients in your blood, or have you progressed measured by a naturopath. Doing this will also make you more determined to finish. And when you fast, nibble on some substitute salt. This will even your electrolyte balance.

Kristen's picture

Be gentle and careful!

I think its great that you are ready to make some changes, but I would work into fasting slowly and carefully. Your body is quite likely a "toxic wasteland" and the detox symptoms could be overwhelming and possibly discourage you from following through with your goals. If I were you I'd do a lot of reading and research (there are tons of books and online material) in order to prepare yourself mentally for the challange. Also, perhaps you could ease into it with a 24/36 hour fresh veggie juice fast, followed by a week of raw fruits and veggies, then a 3 day veggie juice fast, a week or more of raw fruits and veggies and then consider a pure water fast. Juice fasting is cleansing as long as its not too sugary with fruits and allows for slower detoxing.

suggested book- Miracle of Fasting by Paul Bragg

Good luck!

Anonymous's picture


Glad to see someone mentioned the Paul Bragg book. That was my fasting "bible" back in the '70s. I'm wondering if the book is considered "old school" by now, hahaha. But it and fasting made for an amazing time in my life. I'll never forget the passage in the book, where well into a fast, Paul felt a sudden bowel movement coming on at the beach. When he found a secluded place, to empty out, he noticed a silvery substance in his stool. He later had it analyzed as--talk about toxic!--quicksilver!

Anonymous's picture

I have read that passage and

I have read that passage and it amazed me to think that after all those years you still have gunk in your bowels.
But yes, it is a great book and I am currently reading it. It don't think it's old school, it's probably the most up to date.

Anonymous's picture

Good comment. I am trying

Good comment. I am trying to get through a 24 hour water fast, and it's difficult. I am like the guy who has drank too much and have had too many cigarettes. However, I only do it once or twice a week and I tired of it. So I am fasting to revert some of the cravings...developing a tolerance to not eating, I think has to be established, before going on a 21-day fast.

Anonymous's picture

It's been a long time since I fasted.

I know what you mean about it not being easy.. But I decided last night.. I am going to go on a fast.. This is my first day and I am so tempted to eat what my kids are eating.. I know that I will thank myself for sticking to it in the end.. I used to fast when I was younger.. My mom told me years ago.. "after the third day you stop feeling hungry" I tried.. I think I tossed and turned all night for the first 2 nights.. (I tend to eat more at night) After the third day I wasn't hungry.. I felt light and had energy.. It was like this hump I had to cross over. I fasted for 4 days. But I continued doing this through out my teenage years.. And the result? I was at a perfect weight and felt really good. Now I am close to 30. I have three kids and always used the fact that I have to feed them as an excuse. I just quite smokeing, and very over weight. So We'll see what happens.. Also reading all of these post has encouraged me.
Thanks Everyone!

Louise Williams's picture


A good book to read for you is Aronld Ehret's Rational Fasting. It talks about the benefits for those who drink alcohol and smoke. Good luck.

James's picture

Well I did 7 days of veggie

Well I did 7 days of veggie juice and I would make some lemonade in morning after a small workout. I took 3 days of just water then went to a raw fruit/veggie diet. To be honest, I feel better than I have in my whole life. I lost like 15lbs in no time at all. I did have some rashes and my tongue got a little crazy but I hope to go back into another 10 day or so juice diet. Thank you for the advice!

Steph's picture

I would start the 21 day

I would start the 21 day water fast right away. Only drink clean spring water when you do drink it and also, if you drink too much water at a time it will make you a bit sickish. You should be able to tell when you've drank enough. When you get back onto food make sure you start with clear juices then friut and then simple green salads. Getting on the wrong kinds of food too fast will result in hurting your kidneys and also your appendix. Good Luck. (I'll bet it'll stop all those cravings too)

Naturebunny's picture

My fasting experience so far.

I'm on day 9 of a 21 day water fast and I've already lost 16 lbs. I no longer feel hungry, and as long as I get enough sleep I feel energized and light and alive. It's a very rewarding experience so far and I have no desire to quit before the 21 days are up. After the 21 days I plan on slowly refeeding by doing a week on pure fruit / vegetable juice and then a week on raw fruits and veggies. When that's over and done with I'll be adopting a vegan diet. i'm already a lacto-ovo-vegetarian so it shouldn't be hard. the elimination of all these toxins in my body has really made me realize how important it is to take care of our bodies and watch what we put into them! It has been such a rewarding experience so far that I think I will probably do this once a year.

Peter Petrovich's picture

Fasting - Highly Beneficial to Body and Mind

Fasting is an excellent ecercise that everyone should do. I am deeply in love with fasting and stronly recommend it to everyone. If you want to fast, but can not make up your mind when to start, let me know so we can fast together. This really works.

Sheryl's picture


Hi , I read your comment..,.this is my first fast...and am not sure what to expect...are you interested in fasting with me by any chance?

Where are you?

Joan's picture


Hi Peter,

I am curious what your experiences have been with fasting. I would like to start one on Saturday and go as long as I can. My main concern is vitamin and mineral deficiencies, particularly calcium. Can you comment on that? Do you take vitamins along with the fast, or do you include anything else, such as fruit or vegetables. Personally, I would prefer foregoing everything -- I grow tired of figuring out what to eat every day. I try to eat healthy, but sometimes fall off the wagon. I also drink Synergy, which is an Organic & Raw Kombucha tea --I'm truly addicted to it. It's very low in sugar, but is beneficial to the body. I would like to include at least 1 bottle of the tea along with a water fast. Any comments would be most appreciated.



Katy's picture


Hi there,

I need to do a fast soon (like in a week time) for health purpose and general wellbeing. You said to let you know so I am hoping that you can help me fast. I am also trying to beat asthma. I have quit smoking for good a week ago and feeling better already.
I have fasted before for 3 days (years ago) and felt amazing by the 3rd day.
If you are still up for it I will let you know when I am ready again and maybe you could guide me.

Many thanks


Janie Barbosa's picture

I also need to start the 21

I also need to start the 21 day water fast
heath resons i would like to start with you thanks


Anonymous's picture


I really enjoyed your paper, and your references.

I just started water fasting one day a week. Is that enough time to make a difference? So far I feel I have more energy, but it may just be my mind tricking me. Is doing it that often harmful?

Anonymous's picture

I too have been water

I too have been water fasting one day a week since 12/07. I have been very healthy despite exposure to many people with colds and flu, and I have slowly lost about 10 pounds. I plan to continue this regimen forever. It works for me.

Nin's picture


That's interesting. Some people state that you can only reap the benefits of fasting by extended fasts, but a study says that if you fast every other day, you get a longer life. I suppose that once a week would be beneficial too.

Anonymous's picture

I did a fast years ago and

I did a fast years ago and felt amazing. My skin was clear, my hair shiny, soft and full. I felt like I had tons of energy.

Since then, I've tried to do fasts again but with limited success. It's hard to concentrate on detox when you work a couple of jobs and have other responsibilities on top of that. You have to do a fast the right way and doing it 'half assed' really proved more detrimental than helpful. I ended up with iron-deficiency anemia and too much weight loss after numerous 'partial fasting' episodes. I also developed some weird food obsessions. If you have any eating disorder history, fasting is not an excuse to fall back into negative food perceptions. Feeling 'guilty' about eating is not healthy.

Anyway, I do believe in fasting's health benefits when it's DONE RIGHT. Anyone considering a fast should do lots of research before undertaking one.

Rhonda Hunt's picture


I've just started delving into this practice, and I must say that just doing it for 2 days was an eye opening experience! I am going to experiment with this more. It's a wonderful test of discipline and I did not let myself down!

I feel much better after a fast and almost guilty about eating afterwards, but I go back to eating slowly and more controlled! It's great!

Skanda's picture

Forms of Fasting

The hindu religion recommends it in daily life. Fasting is a closely followed practise within Yoga just like medication.

It has increased the life span of the sages in the Himalayas. Apart from food fasting there is also a fast where you keep silent (do not speak) for days. This was followed by Mahathma Gandhi which gave him so much spiritual power to his tiny frame. He did this every Sunday-complete fast (food and silence)

Sandi's picture


I did a 10 day water fast in February and another 5 day water fast in March. I plan on doing 5 day fasts each month or so to maintain the benefits.

The best benefit is that my hayfever went away. No more stuffy nose or itchy, watery eyes! (Yay!) I also kicked my caffein and sugar cravings. I felt such a sense of peace after the first 3 days on the fast. It is truly amazing.

Madhumatidasi's picture

Fasting and acidity

I suffer from acute acidity. I have to eat small portions every two hours - if I don't I get pain due to gas formation. I wonder if fasting is advisable for me.

daniel rogerson's picture


I did a 50 day water fast and wow it changed my life. I wasn't angry with people anymore and I had more peace within myself. There are poisons, toxins and parasites that leave your body when you fast. Poisons, toxins and parasites make people bitter, angry, depressed, and makes you do many other crazy things. I highly suggest it. It doesn't cost you any money and your actually saving money by water fasting.

Mozkyna's picture

water fast

I would love to get in touch with Daniel Rogerson, who have done the 50 day water fast. I have attempted fast and lasted 7 days. Im starting another one tomorrow and aiming for 14 at least.

I would love to talk about this topic more


Katie's picture

50 day fast

How did you stop the hunger cravings? when did these get better? How much weight did you lose?- sincerley interested, katie

juan carlos's picture

50 days on only water? did

50 days on only water?
did you do normal life?
did you stay in bed?
did you eat somethis to get you by?

Anonymous's picture

water fasting

I'm water fasting for 21 days plus doing an enema 2 days a week. Can you tell what is this white stuff that looks like very small clear white thing that is coming out of my bowel and there is probably hundreds of these things sinking to the bottom of the toilet. I don't thinks it is parasites. What do you thinks it is?

Anonymous's picture


It could be mucus or some type of stone like gall stones. It sounds like you're being healed of something.

Louise Williams's picture


I have never fasted for 50 days on water only, but fasted for 30 days and 30 nights on water only. This was an outstanding time of my life. This happened before I even knew about fasting. However during the fast I ran 3 miles every day.

Before beginning the fast I was told I had hypoglycemia by a nutritionist. At the end of my fast, I had complete blood work and I was completely healed.

I lived a normal life, ran every morning, attended to business throughout each day, attended luncheon and dinner meeetings where I drank water only. I was not hungry. I was peaceful and even had to cook for my 13 year old daughter.

There are some great books on fasting and one that I love is Rational Fasting by Arnold Ehert.

For the first three days of the fast I was a little weak, but on the third day I had so much energy.

Good luck.

Cin's picture


I am currently attempting a fast and have found the water from young coconuts good for giving me energy. ( much more than just plain water.) Is that still considered a fast? Is there a naturopathic doctor in the bay area.( San Jose Ca ) that I could consult too. Is there a good place to look for one in my area.

Wesley's picture

Careful with the coconut

Careful with the coconut water. Too much of it will give you diarrhea which will dehydrate you.

Anonymous's picture


I am 52 and look 10 -15 years younger.
I have typically used fasting as a method for weight controll.

I look and feel better when I fast..I feel my worst after a big meal

Ken's picture

Fasting question


I read your comment on the SErendip webpage regarding your practice of fasting over the years. I'm curious to know how frequently you fast in a given year and how long for each fast. Thanks.


Mirian's picture


I am writing an essay paper for my Final exam in my Physc class are Argosy University (California Campus). I would like to use your above description as a testimony, would you let me and can you give me more tips on this topic.



ewane's picture

fasting during exams

please i will like to know if it is good to fast during exam periods.

fasting before exams's picture

fasting before exams

I fasted before exams and it was able to learn and absorb information like crazy. It was better than ever. Not only I passed those classes but I was able to use more time studying since I did not have to eat or party. I think fasting helped me to pass a class of computer science that I was almost failing at that time. Make sure you startin fasting a few days ahead of time, so when exams come, you are at your peak. good luck!!!

Deborah's picture


I tried a fruit fasting for 21 days and it's helps because am not depressed anymore and I sleep better now and even loss 42 pounds... For me fasting is good because it helps me and am planning to do it again soon.

Margot's picture

Concering Fruit Fast

Hello. I am writing to you because my family and I are looking into trying fruit fasting. The question I have is this: When you fasted for 21 days, what did you eat after that? Did you gain the weight back or can the weight be gained back if you start eating breads and meats again?
Thank you for input and I look forward to hearing your advice.

Post new comment

The content of this field is kept private and will not be shown publicly.