On the first few days of the fast a massive amount of water is lost, even though drinking water is allowed in this type of fast. A significant amount of glycogen is lost as well. This is no surprise. About 2.6 g of water are lost for each 1 g of glycogen lost. That is, water is stored by the body proportionally to the amount of glycogen stored. People who do strength training on a regular basis tend to store more glycogen, particular in muscle tissue; this is a compensatory adaptation. Those folks also tend to store more water.
Not many people will try a 30-day fast. Still, the figure above has implications for almost everybody.
One implication is that if you use a bioimpedance scale to measure your body fat, you can bet that it will give you fairly misleading results if your glycogen stores are depleted. Your body fat percentage will be overestimated, because water and glycogen are lean body mass. This will happen with low carbohydrate dieters who regularly engage in intense physical exercise, aerobic or anaerobic. The physical exercise will deplete glycogen stores, which will typically not be fully replenished due to the low intake of carbohydrates.
Light endurance exercise (e.g., walking) is normally easier to maintain with a depleted “glycogen tank” than strength training, because light endurance exercise relies heavily on fat oxidation. It uses glycogen, but more slowly. Strength training, on the other hand, relies much more heavily on glycogen while it is being conducted (significant fat oxidation occurs after the exercise session), and is difficult to do effectively with a depleted “glycogen tank”.
Strength training practitioners often will feel fatigued, and will probably be unable to generate supercompensation, if their “glycogen tank” is constantly depleted. Still, compensatory adaptation can work its “magic” if one persists, and lead to long term adaptations that make athletes rely much more heavily on fat than the average person as a fuel for strength training and other types of anaerobic exercise. Some people seem to be naturally more likely to achieve this type of compensatory adaptation; others may never do so, no matter how hard they try.
Another implication is that you should not worry about short-term weight variations if your focus is on losing body fat. Losing stored water and glycogen may give you an illusion of body fat loss, but it will be only that – an illusion. You may recall this post, where body fat loss coupled with muscle gain led to some weight gain and yet to a much improved body composition. That is, the participants ended up leaner, even though they also weighed more.
The figure above also gives us some hints as to what happens with very low carbohydrate dieting (i.e., daily consumption of less than 20 grams of carbohydrates); at least at the beginning, before long term compensatory adaptation. This type of dieting mimics fasting as far as glycogen depletion is concerned, especially if protein intake is low, and has many positive short term health benefits. The depletion is not as quick as in a fast because a high fat and/or protein diet promotes higher rates of fat/protein oxidation and ketosis than fasting, which spare glycogen. (Yes, dietary fat spares glycogen. It also spares muscle tissue.) Still, the related loss of stored water is analogous to that of fasting, over a slightly longer period. The result is a marked weight loss at the beginning of the diet. This is an illusion as far as body fat loss is concerned.
Dietary protein cannot be used directly for glycogenesis; i.e., for replenishing glycogen stores. Dietary protein must first be used to generate glucose, through a process called gluconeogenesis. The glucose is then used for liver and muscle glycogenesis, among other things. This process is less efficient than glycogenesis based on carbohydrate sources (particularly carbohydrate sources that combine fructose and glucose), which is why for quite a few people (but not all) it is difficult to replenish glycogen stores and stimulate muscle growth on very low carbohydrate diets.
Glycogen depletion appears to be very healthy, but most of the empirical evidence seems to suggest that it is the depletion that creates a hormonal mix that is particularly health-promoting, not being permanently in the depleted state. In this sense, the extent of the glycogen depletion that is happening should be positively associated with the health benefits. And significant glycogen depletion can only happen if glycogen stores are at least half full to start with.
Reference
Wilmore, J.H., Costill, D.L., & Kenney, W.L. (2007). Physiology of sport and exercise. Champaign, IL: Human Kinetics. [Note: the figure may be found in a different edition.]
63 comments:
I recently went on a 3 day fast for science and to kill any random cancer cells through autophagy. I normally eat less than 75 grams of carbs a day. My fasting insulin level pre fast was 2.7.
I had a tablespoon of coconut oil dissolved in coffee whenever I got hungry which was never more than twice a day.
I took blood sugar readings throughout the fast.
Beginning of fast blood sugar was 95
0-24 hours in the 80s
24-48 hours in the 70s
48-to 72 hours in the 60s
My last reading before I quit at 72 hours was a blood sugar reading of 50. The last 12 hours I was feeling rather weak and spacey although I did go for a 3 mile walk.
My question is because my blood sugar continued to drop throughout the fast, I am thinking that I did not cannibalize any muscle during the fast.
Am I right?
Hi Jake.
A little bit of muscle is always lost, as you can see on the graph (the green areas). For short fasts, the muscle lost is quickly recovered soon after the fast is over, especially if you do strength training.
Amino acid turnover happens all the time. A person under severe stress but not fasting would probably lose more muscle than someone fasting.
Hi Ned!
Thanks.
In my own experience I only gain muscle with carbs in. Means keto/LC gives a great plus in cognitive issues but not physical. Now I try some carb-fat-potein type because huge amounts of protein gives me higher BG´s than carbs (potatoes). Hard work to get body and brain in harmony. Greetings.
So from that graph we see that fat oxidation was roughly 300g per day from fasting days 3-14 roughly, and from there it started to drop VERY slightly. This certainly flies in the face of the claims that "your metabolism slows down if you fast".
The slow down in metabolism is far far slower than what most people would probably predict.
Im wondering how the graph would have looked for a strict ketogenic diet ( 0g carbs per day, about 2000 calories ingested per day ), if it would look at all similiar in terms of the decline in fat oxidation after 14 days.
Btw I came to the same conclusion that it is the act of depleting glycogen that is important, not staying in a state of low glycogen availability.
That graph just gave me the idea that dieting would probably be alot more successful if people had a accurate and constant way of checking thier fat loss other than weighing themsevles on the scales. Imagine a handy little wrist watch gadget that was able to show you in real time your exact fat oxidation rate and progress.
Seeing the actual numbers would be a big 'reward' stimulus for the brain and would fuel motivation for further dieting I believe. That would certainly be a multi-million dollar making product.
You'd probably like www.leangains.com. He uses an 8 hour feeding window daily with a BCAA supplement pre workout to prevent muscle atrophy and carb cycling to replenish glycogen stores. Pretty sweet stuff.
Really really fascinating stuff, Ned... great work. Your posts are so information-dense, which is a big plus for me.
This post would seem to lead quite clearly to the conclusion that carb-cycling diets and glycogen-depleting exercise are Good Things.
It is my understanding that muscle glycogen mostly remains intact for use during fight or flight response throughout a fast. This would seem consistent with the amount of glycogen that we see lost in the first three days.
Can we confirm this based on any type of measurement of how much of the glycogen lost in the first three days is liver glycogen versus muscle glycogen?
Hi Byron.
> ... huge amounts of protein gives me higher BG´s than carbs (potatoes).
I don't hear this often. Do you mean average BG right? Postprandially I would expect potatoes to increase BG much more than protein.
Hi Kindke.
Yes the idea that fasting slows down your metabolism significantly is a myth.
Your idea for an invention would be cool, and would make quite a lot of people more neurotic than they already are.
Hi Jeromie.
Thanks for stopping by. Martin has done a great job at debunking a number of myths related to fasting.
I find his ideas regarding IF + BCAA supplementation very interesting, and somewhat intriguing.
BCAAs (leucine, isoleucine, and valine) are essential amino acids, and also ketogenic. But their concentration in muscle tissue is not nearly as high as that of other amino acids, like glutamine.
I'm working on a post on the amino acid composition of muscle tissue. I think it will surprise some people.
Hi Nathaniel, thanks. Yes, those are two very good things, especially when done together. Under glycogen depletion the liver uses fructose for glycogenesis, and not for fat production and release in VLDL particles.
Hi Geoff.
Glucose for brain and other tissues that absolutely need it (red blood cells) comes from liver glycogen and muscle protein. The latter via gluconeogenesis, which is increased via cortisol. Cortisol levels are elevated during fasting.
Muscle glycogen is not released unless it is "unlocked" by muscle activity, which generates lactate. That lactate goes into circulation and is used by the liver to build more liver glycogen.
The authors don't tell us that but it is reasonable to assume that the data was collected from folks who were not completely immobile during their fast. Maybe they even did some exercise at the very beginning. If this is correct, some of the glycogen lost was from muscle.
looking forward to the amino acid post!!! i have been delvinginto its research in some of my endocrinology books...and esp glutamine...
to add to the protein vs carb response... protein makes my BS rise a lot more as well...but i am not convinced spiking your BS is so bad as long as it regulates itself thru time...also dairy of any kinds spikes my BS, but again its not a concern b/c neither protein of dairy seem to have impact in weight gain
Re: Byron's comment--
I also find it unusual that someone would spike higher on BG than on potatoes.
However, there are some interesting anomalies reported with high protein. A number of people on the Eades' 6-Week Cure have seen their blood sugar spike after meals that were little more than whey protein + BCAAs + cream. (Of course, these are people who are already Type 2, which is why they are monitoring their BG in the first place, so proabably not a good cross-section).
Now, that is just a handful of reports, but as they say, the plural of "anecdote" is data. Some people eating easily digestible protein seem to be able to convert protein to glucose at a rather startling rate.
I have no idea what this means, but some people in what ought to be a highly ketogenic state pump out a lot of glucose.
If you have any idea what is up, please share, as I have been baffled by these reports.
Hi Mal.
You too with higher blood glucose after protein than carbs!?
I am guessing you and Byron are referring to fasting BG. Am I correct?
You BG should be low after a protein meal because protein is insulinogenic.
In fact, BG would go down to hypoglycemic levels after ingestion of protein by itself if not for counter-regulatory hormones like glucagon.
Hi David.
That's interesting. You make a good point regarding glucogenic amino acids - e.g., glycine.
I am wondering if what Byron and Mal are referring to is fasting BG because many people who do LC or IF see their fasting BG go up. Probably a combination of benign physiological insulin resistance + "wake up" hormones.
Btw, I've been doing some research on amino acids in muscle, and the evidence seems to point to an almost trivial result. That is that the best source of protein to build muscle is animal meat (including organ meat, connective tissue etc.).
Here is a study by Gannon & Nuttall showing that a high protein/low carb diet dramatically lowers BG levels compared with a high carb/low protein diet:
http://diabetes.diabetesjournals.org/content/53/9/2375.long
The study was conducted with type 2 diabetics.
Great explanation, Ned; for years now I've seen the benefits of HIIT (read: effective glycogen depletion) and low-carb for health and positive body comp changes.
For the record, though, running multiple 400m intervals while being fasted for 18 hours is NOT enjoyable. :)
Hi Mike, thanks.
Just one more comment on BG elevation based on protein, before I forget. This is consistent with what David said.
It seems that abnormal BG elevation is associated with unnatural protein intake, as in the ingestion of a large dose of protein powder.
Having said that, most of the research I've seen so far seems to suggest that protein supplements are not particularly unhealthy. Certainly not even in the same universe of potential health damage as foods rich in refined carbohydrates and sugars.
"I am wondering if what Byron and Mal are referring to is fasting BG because many people who do LC or IF see their fasting BG go up. Probably a combination of benign physiological insulin resistance + "wake up" hormones."
sorry, i meant fasting goes up with a lot of protein. i find food thats really nutrient dense and conatins a lot of aminos (beef liver) also spikes temporarily my BS. my fasting though is usually in the 70-80 range.
possibly all the organs meat i eat is partial reason to the massive muscle i have put on with IF and weight gain because it has flabergasted me!
do you think there is anything to having a sip of BCAA's before a meal to help with nutrient absorption? the only one i find crucial to a lot of things is glutamine. i am curious as to whteher taking it with my fish oil and multi would be beneficial. i agree i dont use protein supplements/powders.
i do get ridicuously hot and sweaty about an hour or two after i eat a protein/amino dense meal though, like sweaty
or i can just wait until your post :)
I am still puzzling my way through this but does it mean that if someone were trying to lose weight, it might be beneficial to go 2 or 3 days eating zero carb and then have a high carb day and then repeat the process?
I lost a lot of weight (fat, not just water) eating zero carb for several months but never felt well the whole time. I didn't sleep well and had little energy. I don't think I function very well glycogen depleted for an extended period of time.
re: HIIT and glycogen depletion
Seems like in order for high intensity interval training to be effective at depleting glycogen, it has to be done at hyper VO2max. It seems like the effectiveness of the Tabata interval was not just the duty cycle but the level of VO2max. That's my interpretation, anyway.
Hi Mal.
Okay, fasting BG makes more sense. The BCAAs are not necessarily bad, I'm just wondering if they are as good as some claim. Having a breakfast with good quality protein (some eggs and leftover meat) might be even better.
Beef liver is nature's super-multivitamin. It has a lot of good quality protein, and even some carbs (liver glycogen, if the cow was not killed after a fast). Excellent source of vitamins and minerals.
I wouldn't eat too much beef liver if I were you though. Maybe no more than once a week. The reason is hypervitaminosis A. It builds up over time, and all of a sudden you are having nausea, dizziness and other "funny" sensations.
Hi Frosty.
Different people respond in different ways to LC. Some people do quite well with LC for a few days, and then carb-loading (natural carbs, I mean). Other do quite well with long term LC, and even build muscle. They tend to be exceptions, it seems.
The fact that you didn't feel well is a clear sign that something was not really right - your body sending you a message. Generally if you do things that make you feel well (healthy, rested, energetic), then you should keep doing those things, at least until your body sends you a different message.
The exceptions are addictive unnatural things, which may make you feel very well for a short period of time. But those don't usually make you feel so well after a day or so.
Hi js290.
The level of glycogen depletion is directly proportional to three things: how much weight you move, how much (or how far) you move it, and the speed at which you move it.
Sprints cause much more glycogen depletion than bicep curls. Multiple sets of heavy squats are somewhere in the middle. You can even calculate the level of glycogen depletion based on some formulas from college physics, with some simplifications built in.
With sprints you move your full body weight, maybe 100 yards multiple times, and you do that at a relatively high speed (the acceleration really is what matters most).
Ned,
thanks for clarifying. I think your last sentence is the point I was trying to make: intensity of effort, which is measured aerobically with VO2max. I think that's why Tabata's protocol calls for 170% of VO2max which saw anaerobic improvements along with aerobic improvements. For aerobic activity to improve anaerobic metabolism, it must be done at an effort level greater than 1.5x one's max. My guess is that's how one can tap into the primarily anaerobic fast twitch muscles using an aerobic interval protocol and drain its glycogen stores.
The odd thing about muscle glycogen is that, as I understand it, it must be depleted on a cell-by-cell basis. So if glycogen depletion and reloading is healthy, then to do it right one needs to exercise all of their muscles.
That's one reason I try to get a wide mix of activities in every week. I'm very suspicious of the idea that short HIIT stints a few times a week give the body optimal exercise.
I have nothing against HIIT (I even do some). But I also do some intense yoga, and a day of weight lifting, and some long sessions of yard work or house repair. Every muscle cell needs to get its turn to play.
Hi js290.
One thing that is often mentioned and it is true is that muscle fibers are recruited sequentially. You may be exercising anaerobically with a load that allows you to do 12 reps. Still, you may be able to recruit most of the muscle fibers as long as you "go to failure" (which to me is the point where form is compromised).
The problem seems to be when you move to much higher rep ranges, which depends on the muscle used, because at those ranges other adaptations kick in. For example, there may be significantly more storage of fat in muscle. Also, the proportion of slow to fast twitch fibers may actually change, toward the slow twitch end.
Your body responds exactly to the stimulus you give it, but not necessarily in the way you want.
Hi David.
You are absolutely right. Muscle glycogen depletion is very localized. Even similar exercises will lead to different patterns of muscle glycogen depletion.
Another advantage of doing whole-body workouts, in addition to more widely distributed glycogen depletion, is that the growth hormone response is much higher. This is especially true for large muscles - legs, chest, back.
The disadvantage is that, after a year or so training, most people seem to have difficulty generating the stimulus needed to push their muscles into supercompensation territory doing whole-body workouts. They would need a 2-3 h whole-body workout, but a workout that long would probably not be productive for most people. The result would likely be muscle catabolism. Those folks then split their workout.
Perhaps it is not natural to go beyond a certain point of muscularity, even if you can. But if you are a professional athlete, doing unnatural things is usually the "name of the game".
Wilmore et al. (2007) is a text, which I do not have access to. Can you tell me where they got the information from? What study are they getting that weight loss data from?
Thanks.
Hi RRX.
I think that is from the authors' own research. Usually I mention any original research that is cited, when I see citation. I have to double check this one, but I don't think there was a citation.
An interesting article from a running magazine on glycogen depletion:
http://runningtimes.com/Print.aspx?articleID=19425
Links on to a Danish medical reseach center called the Centre for Inflammation and Metabolism that is doing some fascinating work.
Nice link David, thanks.
I've heard a lot about "running on empty" for very long distance runners. That makes sense, since fat oxidation is the main fuel for that type of activity.
Still, if a marathoner needs to sprint toward the end to pass a competitor, he or she will "hit the wall" if they are running on empty.
RE compensatory adaptation to burn more fat, see this post for a real life example of how training took a "sugar burner" and turned him into a "fat burner" http://alancouzens.blogspot.com/2008/06/mummy-returns.html Seemed to involve very easy training, something that doesn't come naturally to motivated and competitive athletes. He got his fat oxidation up to 10cal/min- pretty amazing.
I agree with you about the glycogen depletion, but believe that glycogen repletion occurs so rapidly even on low carb (to a sufficient amount anyway) that you'd probably not even notice it was missing (unless you're a sugar burner, in which case you're at a severe disadvantage). Even when running on empty (like at the end of a marathon as you suggest), you can still summon a sprint most of the time. Much of what people think of as physiological limits are in fact under control of their brain which is monitoring energy stores and rationing energy to the allotted distance or time. So when you can see the finish line, the energy returns as if by magic.
Cynthia
Hi Cynthia.
Very good points, and thanks for the link. Btw, I think this post is consistent with one you wrote recently on your blog about your bioimpedance scale giving you BF estimates that looked higher than they should have been.
Regarding fat oxidation; indeed it seems to be the key to a number of health-promoting effects. Other commenters have brought up this issue before here as well. Notably John, who is a sprinter and often comments here, noted that fat oxidation is positively associated with longevity.
However, I think there is a U-curve pattern somewhere here. This is in regards to endurance running and fat oxidation, and more broadly related to fat oxidation and health in general. Something that has not been seriously explored before in empirical research.
I think that someone who routinely pushes herself to sprint at the end of a marathon, with a glycogen tank deplete, will achieve compensatory adaptation over time. However, that may not be entirely health-promoting. A few of the adaptations: (a) more fat will be stored in muscle tissue, which is not particularly healthy; and (b) the body will become more effective at using muscle tissue for gluconeogenesis, so that glycogen can be replenished based on muscle to support those sprints. The latter is not particularly healthy either.
Now I'm current. I've read your first post to this one. I have a lot to think about.
I really appreciate the posts where you explained statistical limits and mis-perceptions.
Hi Ned,
Thanks for the fascinating post. I'm having trouble finding the table in Wilmore et al. From your citation it sounds like the fourth edition, but table 14.8 is different in that edition.
Could you please tell me the edition and page number? Thanks very much.
The purpose of WIC, is targeted nutrition for infants and children, it is not what adults eat and it is more of an education and first resort program , the problem is “junk food” is hard to define, is a buttery chicken junk food, how about juice that has more calories than sugar, or buttery bread, lets ban butter and bread, or only allow whole wheat bread, junk food so to speak is cheaper than boneless chicken and fresh veggies , in addition not all sodas and teas have 16 packs of sugar, chocolate milk is just as unhealthy, why not ban pasta , its full of carbs, white bread is just as bad as soda, let us ban potatoes since you can make fries. Let us ban sweetened yogurt , yogurt has a done of calories that can make you fattening.
Where did you get this graph. I did not find it in the book. Where does the research come from. Can you give me a direct source.
Hey Ned, I was wondering how much fat, muscle and water is regained duing the recovery from a fast. I have heard people say that they put in muscle after fasts, but other people say that was glycogen and water stores. Due know how much was actually muscle and how much was fat?
Hi Ned. I am intrigued by these results, and I couldn't find it in my edition of the book. Do you have any reference to the study the data is from?
He invented the graph. Knowing his interest in health and statistics he probably went on the water fast himself, documented the results and wrote the blog post you see here. However, because of the controversial nature of a fast he couldn't say that is what he did, which is why is attributed it to the book. But as many people have pointed out-- it's not in the book.
Monitoring old posts is a full time job folks. I was told that this one was causing controversy. Well, creative explanation Anon! Sorry to disappoint you, but the most likely explanation is that the graph was in previous editions of the book and then was removed in later editions. I’m not sure why; they may have a better graph now.
Is there anything in the newer editions contradicting this graph? Most evidence I’ve seen so far supports its basic premise: a small loss of protein, and a bigger loss of fat, over time. The protein is lost to feed the glucose needs of the brain. Most of what is lost early on is water.
I own that EXACT edition. Your graph looks nothing like the ones in the book-- the art is completely different. And figure 14.8 is the influence of dietary carbohydrates on muscle glycogen during repeated days of training. Either make a scan of the book with the photo in it and put it on here or tell us where the research came from. ALL the graphs have sources of where the research originated. There should not be an exception. This is a FAKE.
Hum. Okay. So you think I faked a graph and put it here? And why exactly would I do that?
Btw, have you tried looking at other editions of this book? Dated before and after the one you own?
I don't know why you would fake it. But you're a man of science, so you should understand that research claims need to be backed up. I have looked at other editions. I guess I should just contact the publisher and ask them to verify your graph since you don't seem willing to do it. I find it extremely odd that you apparently own the only book with this graph in it. Why don't you pull it out and tell me where the study came from that this graph is based on? That would be a start.
Anon, what makes you believe that I own this book? Has it occurred to you that I may have access to many exercise physiology books through libraries?
You stated very clearly that I faked a graph and put it here? I am still trying to understand exactly why would you think I would do that.
Don't you think a person should have a very strong motive to do something as stupid as that? What is mine?
Ned, I don't care about your motivations for faking the graph. I still stand by my original hypotheses.
All I know is that graph in your article is not in that book. Instead of arguing with me you should be trying to find the true graph yourself and support your article.
Do a google search on the graph and you are simply directed back to your site. There is no cross reference to a study in pubbmed and no one else on the entire world wide web references it or uses it on their own. Instead, people refer to your link... it's impossible that you are the only one to ever site this study and the statistics along with it.
Again, I don't care why you faked it. I just want you to admit you faked it or PROVE otherwise.
Anon, you make some reasonable points, which contrast with your bizarre accusation.
I suggest you follow through with your threat of contacting the publisher. Feel free to post the results of your investigation here.
I'll be happy to correct the post if I made a mistake. But I am sure you'll find out that your bizarre accusation is wrong.
I would never make up a graph.
So, as you suggested, I made good on my threat. I am awaiting an answer from the publishers regarding editions one and three of the book.
The graph is definitely not in editions four and five. I received a response from one of the authors directly.
"This was never in any edition of my book, as far as I know. I have only been involved since the 4th edition.
W. Larry Kenney, Ph.D.
Professor of Physiology & Kinesiology
102 Noll Laboratory
Penn State University"
I found a second edition of the book and table 14.8 is on " The effects of increased training volume on blood lipids and lipo-proteins in male collegiate swimmers." Not quite the same as water fasting.
At the very least you had the source wrong. You said you would correct any mistake you made. Since you say you have access to a library perhaps you should find and photocopy figure 14.8 from editions one and three and post them on here to prove it indeed came from an earlier edition of the book. If it is not in editions one or three, you owe your readers an explanation and a correct source.
I still maintain you made it up. At this time I have no way to prove that, but I'm working on it.
Well, I have to thank you Anon for doing this. Keep digging.
I assure you the explanation will be very close to what I guessed - differences across editions.
You may prove that I made a mistake. You will never prove your fabrication hypothesis though.
From Dave Costill, author involved with all the editions:
"Michelle,
I never saw that graph and I doubt that my co authors have any idea where it came from. I looked at some of my other editions and can't find it either. My guess is it was contrived by the person in question. I never did a 30 day fasting study.
Dave"
I am still waiting for you to correct your mistake or prove where it did come from.
Am I supposed to believe that a highly respected award-winning researcher and professor (Dr. Costill) decided to join someone who hides behind "anonymous" in slandering me?
This seems more like cyberstalking by a troll who is not even smart enough to cover his or her tracks. This person has assumed different identities here, and apparently does not know that anonymity on the Internet is a myth.
Hey Ned, this article has really kept me going on my water fast! One of the biggest difficulties I have concerning water fasting is the social negative pressure. And one of the biggest arguments I receive from reasonable people is that I'm slowing down my metabolism - which seems very illogical to me, because mathematically how is your body going to perform the same functions with less energy? I don't know who came up with this myth! Anyways, the real reason I came here wasn't to complain, but to share a rough calcuation I just did. I wanted to see if the daily calorie amount of macronutrients burnt during the first 10 days would significantly decrease over course (meaning metabolism slowdown). And here is what I found, based on the graph and measuring the amounts with a ruler, calculating 4 kcal for each gram of glycogen and protein and 9 kcal for each gram of fat:
Day 1: G: 190 F: 155 P: 53 Kcal: 2367
Day 2: G: 190 F: 155 P: 53 Kcal: 2367
Day 3: G: 100 F: 185 P: 90 Kcal: 2425
Days 4 to 10: G: 0 F: 222 P: 60 Kcal: 2238
From 2367 kcal to 2238 kcal there is a difference of 129 kcal. It seems pretty natural to me that without the need to digest food, and with a few pounds less your body starts to need less calories.
What do you think? I'm only guessing.
The graph shows that roughly 50 grams of protein are lost per day after the first few days of fasting, which sounds about right. I've read studies that report ~40g/day.
Most people fail to realize that there's only ~100g of protein per lb of muscle. Look at how much protein is in a lb of chicken or steak.
A 50g protein loss per day is 1/2 lb of muscle per day.
That's not insignificant.
Thanks for re-posting this. I've always believed that water loss precedes fat loss due to a drop in glycogen stores, but I have a puzzle for you. About 3 months ago, I consumed nothing but orange juice and chocolate milk for 2 days. The milk was low fat and I took in about 600 carbs each day. I also lost 6.5 pounds! How did I lose that much weight, when you can't argue my carbs/insulin were low and glycogen depleted? This type of loss doesn't occur when I eat 2500 kcal of a standard american diet.
Hi Audacity17. Sudden weight losses like the one you described are almost always due to water loss. If your caloric intake is significantly lower than that required for weight maintenance, your body will respond in ways that are similar to the responses to fasting. What was your caloric intake? Also, did you lose water through other means – e.g., a quasi-diarrhea.
Hi Ned! I agree that the overwhelming majority of the loss must be water. The question in my mind is, was the water lost from glycogen use, or rather, in the breakdown/elimination of fat. Perhaps you know what amount of water must be used to metabolize fat for energy. How could it possibly be from glycogen depletion if I consumed more than 600g of carbohydrate per day? My understanding is that the respiratory quotient, which gauges the fuel source a person is using, averages about .85 over a 24 hour period....or half fat/half glucose. As to the calories...I consumed about 3200 kcal each day and my resting metabolic rate is figured at 3000. Some friends suggested it might have been due to lowered sodium, or higher perspiration, etc.
https://en.wikipedia.org/wiki/Respiratory_quotient
This post is a revised version of a previous post. The original comments are preserved here. More comments welcome, but no spam please!
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