This is going to be a bit of technical/unapplied article, I’m going to try to keep it short and to the point and mainly it serves as a background for some topics I want to talk about in the near future (especially alcohol) so just be forewarned as you start on this. When people talk about diet, it’s common to divide the various nutrients that humans consume into two gross categories which are:
- Macronutrients: nutrients consumed in large amounts (‘macro’ = large)
- Micronutrients: nutrients consumed in small mounts (‘micro’ = small)
So macronutrient refers to protein, carbohydrates, fats and alcohol, those nutrients that, when they are consumed are generally consumed in gram or larger amounts. The micronutrients refers to vitamins and minerals which are usually consumed in very small amounts (e.g. the DRI for Vitamin C is 60mg where 1mg is 1/1000th of a gram). I’m not going to talk about micronutrients in this article and will only focus on the macronutrients, specifically protein, carbohydrate, fat and alcohol.
I’m also going to assume that you’re getting your nutrients through food and it’s going in through your mouth. Certainly nutrients can be given via infusion but this is usually done in a hospital setting (sometimes athletes will rehydrate and carb-load with IV fluids and glucose, mind you) and I’ll assume you’re not doing that.
Digestive Efficiency and Your Poo
Clearly anything you eat has to go through the process of chewing, swallowing and into the stomach for digestion. There a bunch of stuff happens where the nutrients are broken down to one degree or another.
And either they get absorbed (moving into special cells to be released into the bloodstream, or lymphatic system in the case of dietary fats) or not. If you’re particularly interested in the digestion processes of the different macronutrients, I’d refer you to the specific articles:
A Guide to Dietary Fats for fat digestion.
A Guide to Dietary Carbohydrates for carb digestion.
A Complete Guide to Dietary Protein for protein digestion.
Nutrients that aren’t absorbed in the stomach move further down the intestine where in some cases, they are digested by special bacteria and re-enter the bloodstream as short-chain fatty acids. This is especially true for soluble fibers.
Nutrients that pass that stage eventually come out the other end in your poo and we needn’t talk about that much more. I’ll only note in this regards that digestive efficiency in humans is generally very high. Fats are absorbed with about 97% efficiency (e.g. if you eat 100 grams fat, you’ll absorb 97 grams of them).
Animal source proteins are about 90-95%, vegetable source proteins can be in the 80% range and carbohydrates vary drastically depending on their form, fiber content, etc. But for the most part, with the exception of high-fiber foods, you’re not losing a lot of calories in your poop.
I would note, having said more about poop than necessary at this point, that there appears to be slight differences (based on the gut bacteria present) in how efficiently individuals absorb calories from the diet but this only amounts to perhaps a 100 cal/day difference between the highest and lowest people. Of course, in cases of specific disease where there is nutrient malabsorption, all these comments go out the window but I won’t talk about that here. I’ll assume you have a normally functioning gut, etc.
The Fate of Nutrients: Oxidation or Storage
.So what happens after nutrients get through the stomach and intestines and into the body? Broadly speaking, there are two primary fates for nutrients at this point which are oxidation or storage. A third that I should at least mention is that, under certain conditions, nutrients will sort of “sit” in the bloodstream either causing problems there or eventually being excreted in the urine. Outside of various pathophysiologies (e.g. runaway diabetes where glucose is lost in the urine in large amounts), the urine excretion route is generally minimal approaching insignificant and I won’t focus on it further here.
Oxidation simply refers to the direct burning of fuels for energy. This can occur in the liver, skeletal muscle and a few others places and all 4 macronutrients can strictly speaking undergo oxidation after ingestion. So fatty acids from dietary fat ingestion can be used to produce energy, carbohydrate can be burned off, a little appreciated fact is that under normal circumstances as much as half of all dietary protein ingested gets metabolized in the liver via a process called deamination with some of it simply being burned off for energy.
Storage should be fairly clear and the nutrients (with the exception of alcohol) can be “stored” in the body for later use to one degree or another. Carbohydrates can be stored as liver or muscle glycogen, under rare circumstances they are converted to and stored as fat. Dietary fat is stored either in fat cells or can be stored within muscle as intra-muscular triglyceride (IMTG). Under certain pathological conditions, fat gets stored in places it’s not supposed to go, a situation called ectopic fat storage.
For decades it was thought that there was no real store of protein in the body but it looks like this isn’t the case. After large protein meals, the body makes visceral (gut) proteins which can be broken down and released between meals. Skeletal muscle is also , in essence, a ‘store’ of protein in the body but you don’t really want to break it down to use other places. There is no store of alcohol in the body and it must be burned off immediately after consumption.
Which is the segue into the only real point I have to make in this piece: as it turns out, the size of a nutrient’s store in the body is inversely related to the body’s propensity to oxidize it after ingestion. This is especially true in terms of the size of the store relative to the amount consumed on a daily basis.
Put a little more clearly, the better the body’s ability to store a given nutrient, the less it tends to alter/increase oxidize that nutrient after ingestion. And vice versa, the smaller the store in the body of a given nutrient relative to intake levels, the more likely the body is to oxidize that nutrient after ingestion. I’ve shown the implications of this in the table below and will make comments about specific nutrients below that.
Now let me look at the specifics of each.
Dietary Fat: Storage vs. Oxidation
Body fat stores are effectively unlimited as individuals reaching 1000 lbs (and 70-80% body fat) have demonstrated. Even a relatively lean male at 180 lbs and 12% body fat is carrying 21 pounds of fat. Each pound contains maybe 400 grams of actual stored fat and that means about 8500 grams of fat stored in the body.
Contrast this to a relatively high daily intake of perhaps 100-150 grams per day and you can see that the body’s store of fat is much much higher than what you eat on a day. And most people aren’t 12% body fat.
But for the most part, ingested dietary fat has little impact on fat burning in the body; that is, when you eat dietary fat, your body doesn’t increase fat oxidation. One exception is if an absolutely massive amount of fat (like 80 g) is consumed all at once but even then the effect is fairly mild.
Some specific fats, notably medium chain triglycerides, are somewhat of an exception to this; they are oxidized in the liver directly. Rather, the primary controller of dietary fat oxidation in the body is how many carbohydrates you’re eating, which I’ll explain momentarily.
Dietary Carbohdyrate: Storage vs. Oxidation
For carbohydrate, the body’s stores are relatively close to the daily intake. A normal non-carb loaded person may store 300-400 grams of muscle glycogen, another 50 or so of liver glyogen and 10 or so in the bloodstream as free glucose.
So let’s say 350-450 grams of carbohydrate as a rough average. On a relatively normal diet of 2700 calories, if a person eats the ‘recommended’ 60% carbs, that’s 400 grams. So about the amount that’s stored in the body already.
For this reason, the body is extremely good at modulating carbohydrate oxidation to carbohydrate intake. Eat more carbs and you burn more carbs (you also store more glycogen); eat less carbs and you burn less carbs (and glycogen levels drop).
This occurs for a variety of reasons including changing insulin levels (fructose, for example, since it doesn’t raise insulin, doesn’t increase carbohydrate oxidation) and simple substrate availability. And, as it turns out, fat oxidation is basically inversely related to carbohydrate oxidation.
So when you eat more carbs, you burn more carbs and burn less fat; eat less carbs and you burn less carbs and burn more fat. And don’t jump to the immediate conclusion that lowcarb diets are therefore superior for fat loss because lowcarb diets are also higher in fat intake (generally speaking).
You’re burning more fat, but you’re also eating more. But that’s a topic that I’ve not only addressed previously on the site but may look at in more detail in a future article with this piece as background.
Dietary Protein: Storage vs. Oxidation
The body’s total protein stores (and note again that this isn’t a true store in the sense of body fat and glycogen) is maybe 10-15kg or so when you add it all up. Which is pretty high compared to an average daily intake.
The DRI for protein is only about 50-60 grams per day for the average person and even folks eating 200-300 grams per day are still eating far less protein than stored. Which is why protein oxidation rates can change with intake.
As I mentioned above, an under-appreciated fact is that about half of all ingested dietary protein is metabolized in the liver (details on this can be found in The Protein Book). Some of it is oxidized for energy while others are converted into other things (including glucose and ketones) for use elsewhere.
But, protein oxidation rates do change in response to intake. So, when protein intake goes up, oxidation will increase; when protein intake goes down, oxidation rates decrease. This change isn’t immediate (as it more or less is for carbohydrates) and takes 3-9 days to occur but mis-understanding of this process has led to some goofy ideas such as protein cycling.
But it also explains one other issue of importance to protein which has to do with speed of digestion. Early studies, including the oft-cited study on whey and casein by Boirie find that fast proteins are burned off for energy to a greater degree than slower digesting proteins. Since the body doesn’t have anywhere to store the rapidly incoming amino acids, it simply burns off more for energy.
Please note that this does not occur for slower acting proteins or whole foods as their slower digestion prevents the bloodstream from being flooded with amino acids that have to be oxidized for energy. I would also note that recent research has suggested that the body does have a temporary store for protein. Specifically dietary protein in excess of immediate needs is stored in visceral/gut proteins. These can be released into the bloodstream between meals.
Alcohol: Storage vs. Oxidation
And, finally, as noted above, there is absolutely no store of alcohol in the body. None whatsoever. Effectively, alcohol is seen as a sort of metabolic ‘toxin’ or ‘poison’ to the body.
And this means that alcohol oxidation is 100% perfect, that is, the body will effectively do everything in its power to get rid of the alcohol increasing alcohol oxidation to maximum (which means decreasing the oxidation of other nutrients consumed with that alcohol) so that the alcohol can be gotten rid of.
I’m going to ask readers not to read anything into the above paragraph, don’t infer or try to draw conclusions about how alcohol might or mightn’t fit into the diet in terms of anything.
As it turns out, alcohol is an oddity among nutrients with seemingly contradictory effects on things. I’m going to address that in detail in a forthcoming article and, for now, just take the above as some much needed background information.
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Summarizing Nutrient Intake, Storage and Oxidation
And that’s that. After consumption and digestion, nutrients have a couple of primary fates in the body which are oxidation (burning) and storage (for use later). And, as it turns out, the propensity for the body to store or oxidize a given nutrient is related to the body’s built-in store relative to intake.
In the case of dietary fat, where stored fat is much higher than daily intake, the body tends to store incoming fat and burn very little. Fat intake per se has very little impact on fat oxidation rates.
Rather, the rate of fat oxidation is related to carbohydrate intake as the body is able to precisely alter carbohydrate oxidation to changing intake. Eat more carbs and burn more carbs (and less fat); eat less carbs and burn less carbs (and more fat).
Protein is somewhere in the middle, oxidation can increase or decrease relative to intake but the effect takes time (3-9 days). To a great degree there is no real store of protein unless you count muscle and organs. However, there appears to be some short-term storage of dietary protein in visceral/gut proteins.
Finally is alcohol, with no storehouse in the body, alcohol oxidation will take 100% precedence over everything else when it is consumed. I’ll discuss the implications of this in an article on alcohol (and it’s rather schizoid effects on body weight and body composition in a later article).
Similar Posts:
- How We Get Fat
- Calories, Nutrients, or Food?
- What are Calories?
- A Complete Guide to Dietary Protein
- The Problem with Dieting by Percentages
Great read, 1 question though:
“This, along with differences in handling (e.g. the fact that fast proteins are absorbed by the gut as discussed in Casein Hydrolysate and Anabolic Hormones and Growth – Research Review) are a big part of why slower digesting proteins invariably lead to better overall protein retention in the body; not only does more make it into the bloodstream but less is burned for fuel.”
With this in mind, would you still recommend the use of whey-protein after workouts in the UD 2.0 program? What about animal proteins like chicken-breast for instance, I’ve heard that they are to be considered as “fast”. A whey-shake, some chicken-breast or casein-shake/ bowl of cottage cheese, what would you recommend for optimal uptake and muscle-building in the long run?
Article on the effects of alcohol from someone who really knows wtf he’s talking about?
As a college student and a rugby player, [and if you know anytihng about the operation of rugby clubs, you know what i mean], I can’t wait for that article.
I’m waiting for that one too, now that I’m dieting for fat loss I’ve skipped all opportunities to drink (and I’m not even a drinker) in fear of the worst, as I don’t really know one beer or two is “just” 250-500 calories, or it does something more bad (and days of dieting will go wrong, muscles fall off, etc), and if it does, how bad.
Thanks for the article
I’m looking forward to the alcohol article, too. I’ve been doing a form of keto diet since the beginning of January that has involved drinking beer on my Friday evening carb up. It’s the only time I indulge during the week, reasoning that there are some carbs in beer in addition to the alcohol. At any rate, I have lost 25 lbs., so I can say “so far so good.”
I am interested in the alcohol article too. The one alcohol study I had seen was with the test subjects drinking the equivalent of 10 drinks in 1 hour(who drinks that much that fast). I also read Arnold’s Education of a Bodybuilder which talks about drinking lots of beer during and after workouts, also the old time strongmen were known as legendary drinkers lol.
Lyle,
You mention that 10-15kg or so makes up the total protein “stores”.
I would really like to know how the math worked out for these numbers.
Since about 40% of the bodyweight is skeletal muscle, and water is about 75% of the muscle cell – fill in some cellular thingies such as electrolytes, glycogen, etc and we have about 20% of a muscle as actual protein, right?
A hypothetical 70kg male will then have skeletal muscle weighing 28kg, out of which only 5-6 kg is actual protein. What am I calculating wrong?
(please note this is important for me as I work in ICU infusing nutrients in patients)
Many thanks.
Ok, now that I think of it, I realize that in its context it encompasses the entire body proteins including intravascular proteins, organ proteins, etc…
But I still would like to hear you chyme in on the math / and or sources.
Thanks again.
alcohol oxidation is 100% perfect
Somewhere Robert Cameron is having a cocktail and smiling,
Yash–
This might be helpful for you, then: https://www.tmuscle.com/free_online_article/sex_news_sports_funny/a_muscleheads_guide_to_alcohol_1
Written by Alan Aragon.
This comment is a little pre-emptive Im sure, but after reading some articles regarding alchohol oxidation I did an experiment on myself. I was doing RFL and losing weight well but was stressed and also had sleep issues. I added about 500 cals from wild turkey or bacardi 151 (high proof alchohol with as little tag along carbs as possible) a few nights a week and saw no change in my weight loss. I will add that NOT eating after taking several shots is a NIGHTMARE. I generally cant do it, but if I can muster the willpower it doesnt seem to affect my fat loss. I will preempt Lyle here and admit I am fully an idiot and that anyone trying anything similar is being pretty rediculous too. Its worth noting that I was eating about 1200k daily almost all protein and lifting and hiking, so my weight loss would have continued with the addition of 500cals of any macro, its really hard to measure such things with great accuracy. IM lookign forward to the article though, reading pubmed casually is one thing but having Lyle link everything together is much easier to grasp.
I’m also very much looking forward to the article on alcohol. Anecdotally I was a broker for many years, drinking a near-alcoholic level of alcohol on a more-or-less daily basis. I (obviously) got fatter whilst in the job, but my calorie intake from alcohol alone should have been enough to make me obese… would be nice to know what was really going on!
Raidho: In what context? that is, for which part of the UD2 are you asking about? And keep in mind UD2 was written nearly 10 years ago before most of this research had developed.
Yash/Bret/Eric/Neil: Someone below mentioned Alan’s alcohol article and I’d recommend folks to that for the time being.
Elio: I probably pulled the number out of memory without checking it when I wrote the piece, in the same way I screwed up another bit of math that I meant to check (someone caught it for me). But keep in mind that skeletal muscle is not the only store of protein in the body. Organs contain protein, there are proteins in the bloodstream that can be broken down, etc.
Eric: Wait.
“Raidho: In what context? that is, for which part of the UD2 are you asking about? And keep in mind UD2 was written nearly 10 years ago before most of this research had developed.”
Wel, if I remember correctly, it’s after the Tension (and perhaps also the Power?)workout, you recommend whey-protein combined with fast-carbs as a first kick into anabolism. So my question relates to the Tension (and Power)parts.
But then again, also for the depletion-part of UD2, I find the question relevant, casein/cottage cheese based protein, or “faster” types like those from animal meat-sources, what do you recommend constitues a good base of protein in the depletion-part?
Lyle, silly question, but lets say one 166lbs 15%bf male 2 years of training, eats magically 0grams of fat per day.
His maintenance is 2500 calories per day.
But now he is getting 3000calories, 1000 calories from protein, and 2000 calories from carbs.
And NO training at all.(say he stopped 3 months ago..)
So 500g carbs, 50-100 more than whats already stored,
And 250g protein.
Where would this 500 extra calories per day be stored?
if i read this article well, i don’t think he would gain one pound of fat per week, maybe he would increase his carbs storages?
And in situation “B”, say he never stopped training and gets lots of proper training, same calorie distribution.
I don’t think it would all go to lbm because of what you said about p-ratio in UD2.0, but a 80% going towards lbm would be possible?
and if occurs of 400 cal per day going toward lbm, how long would he expect to gain one pound of lbm?
I think the value is different than the 3500 for fat, but i can’t find the value..
And in situation “C” heheeh
Identical to “B” but the guy has 8+ years of proper training (but maybe a different %bf).
i’m asking this last situation because of your article of maximum muscle growth after years of training.
So where are the extra calories being stored, after someone has a lot of proper training and it’s proven that he can’t be putting a lot of it towards muscle growth…
Thanks!!!
Raidho: For depletion, protein powders are inappropriate across the board, you don’t need post-workout nutrition in the first place and should be eating food. For tension, I can go either way with it. A slow protein might be superior but you have to weigh that against the fact that casein/MPI tend to keep people very full and that may make getting sufficient calories in over the length of the carb-load. For power, with the current data set, I’d probably say go with a slower or slow/fast mix immediately post-workout. So casein or MPI.
Bruno: You remember that part in the article where I said “Don’t read anything into this right now?” That was awesome. I may have made the comment specifically for alcohol but it applies across the board. This isn’t the place to discuss your specific question in detail as it would take an entire article to address de novo lipogenesis.
Thanks a lot for sorting this out, really appreciate it!
“Fat intake per se has very little impact on fat oxidation rates.”
In that case why is it that some people are suggesting increasing dietary fat to burn body fat? Martin at Leangains said he ate quite ridiculous amounts of fat and got very lean. Another blog I have read where several people did the experiment of eating excessively high fat up to 6000cal of fat, butter, cream, pork fat and actually ended up after 6 months 2lb lighter. I have been limiting the carbs,0-20g, keeping protein moderate, 60g-80g, and usually a 500-800 calorie deficit most days. I am a 53yo male 58kg. Resistance train 4-5x a week. The reason for the low weight is I am a bi-lateral amputee, r arm above elbow, r leg above knee. I have some fat around the lower abs and back I would like to lose.
Regards,
Alan.
Because they don’t understand physiology. It’s not the presence of dietary fat that increases fat oxidation but the absence of carbs, as the article states. But since you have to eat something; if you reduce carbs, and you’re usually limited in how high protein can go, if you want to avoid massive deficits (ala Rapid Fat Loss), you have to increase fat. That’s all that left.
Basically what I said in the article. But it’s not the eating more fat that is having the effect: it’s the combination of a deficit/eating less carbs.
are you sure about those numbers for digestion-efficiency?
I haven’t directly studied human physiology. On the other hand, I’m familiar with the operation of water&sewage treatment plants; they get significant amounts of methane from the process. Methane is a hydrocarbon which i presume evolves from breakdown of (surprise) carbohydrates.
There are also agri-biz operators who feed livestock poo (one has to segregate the urine away from it) to black-soldier-fly egglings. The egglings literally eat the poo and end up as nice bite-size chunks of protein that poultry and pond fish find deliscious.
So therefore, i have to imagine that mammalian digestive efficiency, can’t be in the high 90’s
Thanks for the article Lyle.
“OF course, in cases of specific disease where there is nutrient malabsorption, all these comments go out the window but I won’t talk about that here.”
I was wondering if you could point me towards some articles or research if any was done on the subject. My girl friend has either IBS or Crohn’s disease (Doctors have been unable to diagnose successfully) and she has had a lot of trouble managing her weight since the issue arose.
Al: Unfortunately, physiology isn’t subject to logic and intuition and digestive efficiency has been DIRECTLY MEASURED in humans with the values I cited having been found. Extrapolating from sewage treatment and lower animals is a mistake.
Carl: Honestly not something I pay massive attention to so I can’t point you anywhere useful. I will note that some work has shown that both probiotics and glutamine can help with gut issues (leaky gut and IBS specifically) since both can ‘heal’ the gut.
Ooh, I can’t wait for Lyle McDonald’s “Absolut Diet” where specific exercise protocols are used to repartition the calories from alcohol straight into muscle =)
Hi Lyle,
First, I would like to say that I am a huge fan of your work, and have successfully completed a 4 weeks run of UD 2.0 with 1.5 inch off my waist and an increase in strength. By the way, UD 2.0 as you’ve mentioned in a previous reply is getting old, what is your most current revolutionary program which delivers this stellar results?
But that was not the main issue.
My question is this:
I will take protein as an example but the same can be asked regarding fats.
Protein, or to be exact, amino acids, are used as the building blocks of our bodies.
When we eat protein this process of building is the oxidation part you’ve mentioned, or the storage part?
When more protein than the body needs for this building process is ingested, while still in maintenance calories, as I understand from your article will not be turned to fat, simply burned for the energy, and no fat mass will be accumulated. Is that so?
The calories are added no matter what I presume.
Oxidation is burning for energy, building muscle is storage. And read How We Get Fat to answer your last question: calories always count.
So you basically say that dietary fat is more likely to be stored as fat than carbs. But you also said that eating less carbs means better fat oxidation. So lets say a person eats the same amount of calories either from carbs or fat, what happens then? Assuming that calories ingested are same in both situations, is eating carbs better than eating fat or it doesnt really matter?
Thanks
Doesn’t really matter outside of interaction with genetics, insulin sensitivity and training.
Thanks for your answer.
Hi Lyle,
Thanks again for everything you provide on this site it’s a constant reference. This topic despite me reading this article a few times is hopefully relevant for my question if you have time to explain things. One thing I cannot seem to get my head around is that carbohydrates ‘store’ in the body is glycogen.
I understand the role of liver glycogen clearly (doing post-graduate nutrition ATM) but I cannot wrap my head around usage of skeletal muscle glycogen’s use in a fasted state. The enzymatic processes of ‘trapping’ glycogen in muscle cells for their use ‘only’ seems counter-intuitive to the idea of conversion to lactate and gluconeogenesis in the Cori cycle for use of that glucose ‘elsewhere’. Are the textbooks just assuming normal conditions here (i.e. people normally eat regularly enough to top up muscle glycogen so it’s use is mainly anaerobic in this instance) and not the person in a fasted state following around 12-24 hours?
Apologies if this is somewhat off topic Lyle, I just can’t get straight answers from resources/lecturers in a flowing way and I figure you’d be the person that can give me the best response.