First off, I'm new here. Hi Second, this post may be long, but I'd rather cover all the bases. I hope you'll take the time to read it, especially if you are interested in fasting.

Two months back I went on a water fasting diet. I did it for 30 days, and I plan on going back on one again very soon. One of the things that amazed me while I was searching for information is that there is a wealth of misinformation on the topic all over the web. I did a search for posts on fasting on this site alone and it was filled with thread after thread of people bashing it, claiming it will kill you, eat away at your muscles and lead you to massive food binges. This was disheartening I'd like to put a few of the myths to bed, if possible, and confirm a few others, because I'd like to share with others what worked for me, and changed my view of food completely.

Now, I'm not going to advocate fasting as the "only way to lose weight" because it is far from it and I realize that. It is not for everyone, and there are certain people who just shouldn't do it (diabetes and heart conditions are a big no no). Everyone is different, so please keep an open mind. I will not be discussing fasting from a detox or religious point of view either.

To start, I'm am still an overweight individual. I am currently at 351 lbs. When I started this diet I was over 400. I can't give an exact weight, because my digital scale didn't go above that. I've tried numerous diets in my life, but the problem was that I always fell off the wagon. I used to eat for depression, celebration, boredom, for the sake of "six meals a day to keep the metabolism up" and any other reason. I was, frankly, addicted to food. Nothing worked until I fasted, and that was because of one simple reason, I didn't permanently change my views of food and eating habits until that point. For any successful diet, this is key. Fasting is no different. What fasting did for me on a mental level is let me break the addiction. It was a chance to start fresh.

With that brief bit of back story out of the way, let's get down to the nitty gritty.

Probably the two most common myths about fasting are that you will gain all your weight back and lose all your muscle. The mechanics behind both of these answers are related, so I'll deal with them jointly. In a short term fast, you will gain almost all the weight back and lose no muscle what so ever. In a long term fast, this is essentially reversed. The only way you will gain back all the weight from a long term fast is if you go right back to unhealthy eating habits once you break it. Muscle, however, is lost during a long term fast but it is an incredibly small amount. It is not the "50% of your muscle is lost in a week" as I've seen claimed on a body building forum or any other obscenely high number. Nor is it your heart, or any other organ, that the muscle is taken from as I've seen still others claim (really, I have). How much do you lose then? What do you keep? Well, keep reading :P

Let's look at how the body deals with the energy we supply it with. Most of what we eat turns to glucose, and this is what powers us. If you do not eat for 8 or so hours, the body turns to it's back up source of glucose in the liver known as glycogen (fancy name for stored glucose), which will feed the body for about 12 hours. After this, it goes for the glycogen stored in the muscle. This is not your actual muscle, just the extra stored energy we keep there (large difference). I've seen varied figures for how long this will keep you going, from 2-4 days with the aid of fat. Once your body starts breaking down fat all remaining glucose reserves are used solely by the brain. After this point you switch entirely to your fat reserves. That means that all your energy consumption is coming directly from fat, this is usually around the 5 day mark.

Each pound of fat has ~3500 calories. A (very) rough estimation of your sedentary calorie needs is weight x 10. So for me, not moving at all, I needed roughly 4000 calories at the start of my first fast to just survive. That's a little over a lb of fat a day being burned. This does not come back after a fast. No fat returns after a fast unless you eat enough food and do not exercise thus causing it to return. Water weight, however, does return. This is most pronounced at the start of a short term fast. As you fast you lose sodium, sodium retains water in our body. Once you return to eating processed food, many incredibly high in sodium, you will retain all that water again. This is usually about 5lbs that you will gain back rather quickly at the end of a fast, that is it. But... what about the muscles?! I know, I've been stringing you along

The loss of muscle during a long term fast comes when that last bit of glucose and glycogen is used up after bout the five day mark. This is why a short term fast (1-5 days basically) will not break down any muscles at all. Once all glucose is used and the body has switched entirely to fat the problem develops. Your brain isn't like the rest of your body, it can not get all of it's energy requirements from fat. Only about 90%. The other 10% must come from somewhere else, and that place is sadly muscles. This leads to the destruction of about 1 ounce (20-30grams) of muscles a day after the ~5 day mark. The math adds up to 1lb of muscle lost every 15-16 days. That means if you water fast for 30 days you'll lose just under 2 lbs of muscle.

With average exercise you gain ~1 lb of muscle a month. That means any muscle lost from an extended fast can be easily gained back as long as you continue a healthy exercise program. Now, if you deplete your fat reserves you will switch over entirely to muscle. This is the clinical definition of starvation, not fasting. Avoid this. This can lead to death. Your body will usually alert you to this before it happens with intense hunger pains at around 5-10% body fat left.

If you have been following this so far, and if you have read up on fasting, you might know that another very common fast (perhaps even more common than water fasting) is the juice fast. This is basically drinking as much freshly juiced and strained vegetables and fruit as you want (along with water). Fruits and vegetables have sugar (glucose), some more than others. Therefore you can completely avoid muscle loss on a juice fast, though you will not burn as much fat. I do not have experience with juice fasts though, so I can't say how much less.

Now, another common myth is that fasting ruins your metabolism. It is true that your metabolism slows during fasting, but it will return to normal once the fast is over. The best way to break a fast is to eat small healthy meals and slowly increase the amount to normal portions over the course of a week. This will ensure no increased weight gain, and return your metabolism to normal. If you do not do this, or if you continue to eat unhealthy, you will gain weight. Fasting isn't a miracle cure.

Malnutrition is another common issue people claim will occur. The human body typically stores enough vitamins and minerals to survive for a month unassisted. However, after that you will be in a dangerous area (also considered a form of starvation and could lead to death). The best solution is a daily multivitamin while you fast, this avoids any potential issue as you will just pee out excess. I personally also took a calcium supplement because Centrom didn't provide the daily requirement.

Okay, I figure I've gone over the biggest concerns in adequate detail. I'll go over some of the other positives and negatives briefly.

So that's it. I hope this has cleared up some of the misconceptions with fasting and opened it up as a viable weight loss alternative to some of you. It really helped me on my way to proper weight loss. I lost 40+ lbs on the fast itself and then 10lbs so far from the healthy eating habits I took up after. It's been a little over a month since the last fast, and I plan on going on another one soon. I would only recommend a true water fast if you have ample time and no real social responsibilities. Take a vacation from work if you do it, or work from home. You will be very weak and most likely just want to read a book or watch a movie the entire time, or take naps You will only have real energy for a few hours every day, and that can be very fleeting.

For the TL-DR crowd, a brief overview. Fasting does not cause significant muscle loss (none during a short term or juice fast). Fasting will not result in rapid weight gain when the fast is finished unless you return to unhealthy eating habits, or simply regain water weight (which is a large portion of the weight lost in a short term fast). Fasting does not permanently destroy your metabolism.

Hi Norska,

Wow! Your a wealth of knowledge! I was just wondering if your doctor put you on this plan or if it was something you took on alone. It does not seem as dangerous as I once thought, especially after all your explanation.

I know that when you do not eat for a few days your body is in ketosis, so that is pretty much the same as a very low carb diet it seems to me.

Well, thank you for all the information! I personally don't think fasting is the thing for me, but I'm glad your having positive results!

It was something I decided on myself a few months ago after extensive research. I thought enough was enough, it's time to get serious about this

And yeah, it's ketosis that burns the fat during a fast, same as a low carb diet and also MediFast.

I'm glad you found it informative.

Sounds interesting!

I'd love to see links/sources for the data you posted above - do you happen to have those available?

For my psych degrees (bachelor's and master's degree), I had to take quite a bit of coursework in human biology, and even though I'm a bit rusty (wouldn't want to take an exam without brushing up), we learned of the many dangers of fasting and both short and long-term nutrient deprivation - and the biological processes that drive them.

Some of what you say is in direct opposition to what I learned. For example, the idea that muscle tissue will be so efficiently recycled (lost in one place and gained in another without significant loss of muscle) doesn't at all fit with what I learned.

We also learned that heart muscle tissue is a very vulnerable organ during fasting. Losing even a fraction of an ounce of heart muscle tissue can indeed be extremely dangerous, and you can't control in a fast WHICH muscles your body will canabalize. You would not want (but couldn't prevent) new calf muscles being built out of muscle lost in the heart. Two pounds of muscle loss may not seem like much, but it can be catastrophic depending upon WHICH musles are affected.



I don't argue with this statement: "Probably the two most common myths about fasting are that you will gain all your weight back and lose all your muscle."

But these are myths because they're overstatements. You will gain your weight back, if you return to your normal eating, and of course you will not lose "all your muscle." It would be impossible to lose "all your muscle" because a person cannot survive long enough to lose all muscle tissue.

-Some claim detoxification effects. This is mostly anecdotal

That's because such claims have no scientific basis. There is tons of research of substances, treatments and actions with alleged "detoxification" properties, and to my knowledge none have shown any sign of any "detox" having occurred.

As I remember it there was more research supporting fasting resulting in DECREASED resistance to stress, not increased.


Because human biology wasn't my field, and because I studied it only incidentally, there's a lot more that I don't know about human biology than I do know. And new research is always changing the way we look at older "truth."

That being said, I'd also like to read the actual research you refer to, before I overhaul my understanding of fasting's effects on the body.

I agree kaplods! Please, please be WARY of this advice I mean no disrespect, but this is much different in some aspects then what I have learned! Please, please if you are considering this pick up ANY college level physiology text boom and allow it to explain this to you!

The mechanisms by which fat is broken down is almost always linked with the breakdown of protein. True, some of this may be glycogen storage, but NOT ALL IS! A lot is free amino acids from the actual proten and even from protein in the liver. Your body starts showing these signs when glucose is low - not just a fast, even between meals, so the effects of fasting would I'm sure be much greater. Glucagon rises in response to low glucose, as well as growth hormone, epinephrine, norepinephrine and acetylcholine to name a few. The primary job of all of these is to save glucose for the brain no matter what and they primarily work in combination with protein breakdown and lipolysis (although not all do). Also, burning only fat is NOT good. Acetyl CoA is what's used in the mitochondria for energy and at some point it can no longer absorb more and ketosis begins. Ketosis is BAD! It changes the acidity of your blood and could eventually send you into a coma. Again, I do not mean to be disrespectful at all, but these are just a few of the effects. Please, please, pick up any textbook and RESEARCH this first.

That is just a very BREIF and SIMPLIFIED summary of what happens - again any textbook would be an excellent reference! I've learned the same thing from intro pyhsiology through advanced courses in th subject and all the info has been the same (almost identical, a few wording differences,etc.)

I'm sorry again, I just can't stop...also please consider the enzymes needed for your ENTIRE body to function Na+, K+, Ca2++, etc.

These are needed for your HEART to work and for your brain to send signals.

When calcium is low (from not eating) a hormone called PTH mobilizes it (steals it) from your bones.

Again, I don't mean to be rude, and I could never fit all of the information here, but please be CAREFUL

Hello Kaplods, nice to meet a fellow psych student! I've just completed my psych/soc double major last year and I'm currently debating whether or not to go on to masters or doctorate. Basically I'm in limbo and trying to figure out what I'd like to do for a living :P

Regarding muscle loss and being "efficiently transferred" that I'm not sure of the particulars to be honest. It's probably the most shoddy of the information I provided, along with the scant mentions of detox, though physiologically it makes sense. (Needing protein to build new muscle, only source of protein in a fasting body is muscle, so to repair damaged or build new muscle requires the break down of muscle.) It was something I've read in passing and can't remember where. However, I wouldn't advise any strenuous activity that would result in the building of new muscle, or to continue fasting while a muscle is damaged, during a fast. Everything I've read about fasting, water fasting especially, dictates that you do it while in a relaxed state. It's best to limit any potential protein needs solely to the brain.

As for articles on that, how the body converts energy and what is "eaten" during a fast, netwellness . org/question . cfm/37350.htm cites the same text I retrieved most of my information from when I was researching this at a local uni. (Krause's Food, Nutrition, and Diet Therapy). This link should be considered a bit more authoritative (and something I wish I found before sledging through the text books myself, to be honest :P) as it is a response from Professor Sarah Couch, PhD in Nutritional Biochemistry to a fasting question. Another article which deals with this is "Feeding, Fasting and Starvation: Factors affecting fuel utilization" which was published in the medical journal Proceedings of the Nutritional Society in 1995.

As far as the muscle taken being from organs, everything I've read indicates that organ and extreme muscle deterioration does not start until the effects of starvation via catabolysis kick in (at this point the body has turned solely to muscle for energy). I have also not been able to find evidence of a heart, or organ related, death from fasting in individuals where a pre existing condition was not present. Again, the cannibalization of organs occurs during catabolysis, not during ketosis. Ketosis is what occurs in the body when insufficient glucose is present and is a perfectly normal, and healthy, response in humans. You can easily find more information on these biological processes in most medical texts.
Exactly! Sadly, the vast majority of people vehemently believe these overstatements. Just perform a search for fasting on this very site and you will find claim after claim that this is the case. That was the primary reason I felt the urge to make this post.

As far as the positive effects go, I've got a list of journal articles and links here so I'll try and break up the links as best as possible since I have yet to reach 25 posts And a word about the poor rats, it is standard practice to test a hypothesis on animals before humans, and they are usually used as a gauge. IE, if the test was horrible for the rats, it will be dropped and never reach humans. However, a properly conducted and reviewed test on animals could lead to human testing, hence why their claims are relevant.

Intermittent Food Deprivation Improves Cardiovascular and Neuroendocrine Responses to Stress in Rats - The American Society of Nutritional Sciences, June 2003

Intermittent fasting dissociates beneficial effects of dietary restriction on glucose metabolism and neuronal resistance to injury from calorie intake - Proceedings of the National Academy of Sciences of the United States of America, May 2003

Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism - The American Journal of Clinical Nutrition, January 2005

Effects of Greek orthodox christian church fasting on serum lipids and obesity - BMC Public Health, May 2003

Every Other Day Fasting May Reduce Cancer Risk - worldhealth . net/news/every_other_day_fasting_may_reduce_cance/

Mice live longer fasting; How about humans? - (Had to retrieve the article from google cache) Sadly I can't post this link without destroying it via forum restrictions, it is from the post-gazette, though as said the real page was down as of this posting but I was able to find it via google cache.

On-off fasting helps obese adults shed pounds - reuters . com/article/idUSTRE5AB4HM20091112

Study: Fasting improves health as much as cutting calories - usatoday . com/news/health/2003-04-28-fasting_x . htm

Hi petlover, just wanted to address a common misconception in your first post, and also a statement in your last post.
This is incorrect. Ketosis does none of that in a healthy human, Ketoacidosis produces those symptoms. Ketoacidosis is not the normal human response. It occurs most often in diabetics (which is why I stated numerous times that diabetics should not fast). Another common culprit is alcoholics, and I would never recommend an alcoholic to fast.
This is one of the reason I specifically stated that you should take multivitamins during a fast. You are talking about a product of malnutrition, not fasting. Prolonged fasting can lead to malnutrition, but a healthy human being generally has enough reserves of vitamins and minerals to survive for a month. As said in my first post though, better to be safe than sorry and take supplements.

I would like to suggest that anyone interested in fasting talk to their physician about this option. It can be risky for certain groups, and only your medical provider knows your exact situation and whether healthy for YOU.

You're right, I was typing very fast on my walk home from class and I did mix myself up. However they are both bad. Ketones are NOT meant to be food for the brain and that is what eventually happens - you cannot function as highly on ketones. Hypolgycemia can definitely induce a coma because the brain can't function efficiently on ketones. (Although from the explanation of my professor who focuses his research on hypoglycemia/hyperglycemia, ironically, you can still have too many ketones and have the actely coA build up without being diabetic).

I was trying to remain respectable, but I feel that maybe I am not getting the same respect in return. I can respect research articles, but not all things that work in mice work in people (leptin), and also it takes A LOT of research for something to be taught/in a textbook, although I am always eager to learn about new research, I simply urge people to pick up a textbook and find out for themselves - or possibly ask a doctor why they all advise so strongly against it.

Good luck on your journey.

Wow. I just begin my journey today and was excited about this site until I found this. I agree with kaplods and petlover (you got a little mixed up, but you fixed yourself).

You need food. Ketosis is not good long term. You will break down protein and it could definitely be heart tissue. Vitamins are not the same as consumption. You can't store water soluble vitamins in excess. How many people eat salt vitamins anyways?

I had heard from friends that this site was supposed to really support healthy weightloss and I am very disappointed. I am starting to think that this is not the place for me if fasting is something that can be supported.

For everyone else, I agree with Petlover - go look in a textbook. That is way you should get your information. Or ask a professor. Or a nurse. Or a doctor. Please.

That's why I advised talking to a doctor...so people can get a medical opinion on this before jumping right into not eating.

Dr. Fatpants - please explore ALL of the areas of 3FC before you make a decision about joining here. It is a wonderful place for support, for all kinds of plans, and I'd hope you'd look around before deciding based on one thread that it isn't the place for you.

DrFatPants - Many things are open to discussion, that doesn't mean they are supported. If someone has an opinion on something, then they may express that opnion and others may discuss with them but that doesn't mean the initial opinion is 'supported'.

As someone who started well in her 300s and is in the low 200s, I have to say that I've eaten every single day I personally am not a fan of fasting.