Thursday, September 10, 2009

Primal Potatoes, Part 2, Reply to Rambling Outside the Box

Well, my post Primal Potatoes, Part 2, appears to have struck some nerves. Drs Cynthia and David posted Primal Potatoes—a Contrary View at their blog, Rambling Outside the Box.

As I read their reply, I don’t see that they addressed the fundamental point of my post, which is that people eating low carbohydrate diets don’t have the same anaerobic capacity as people eating higher carbohydrate diets (although not necessarily “high” carbohydrate diets) that allow for greater glycogen storage. As I noted in my original post, even scientists who advocate ketogenic diets (e.g. Phinney, 1) accept this as an established fact and have demonstrated it themselves in controlled studies on keto-adapted athletes.

Cynthia and David report that one of my links to a reference did not work, so they started off their rebuttal by searching PubMed for the article. In such cases, I suggest asking me to correct it, or provide another avenue, rather than picking another article that has Fournier as an author, and assuming, perhaps wrongly, as in this case, that you have the right article in your hands.

In my post, the dead link referred to this article:

Fournier et al, Post-exercise muscle glycogen repletion in the extreme: effect of food absence and active recovery, International Society of Sports Nutrition Symposium, June 18-19, 2005, Las Vegas NV, USA

This paper includes this quote to which I referred:

“In fact, we store just enough glycogen to sustain our energy demands for only a few hours of intense aerobic exercise (Gollnick et al., 1973; Ivy, 1991), and so little glycogen is stored in our muscles that close to a third to half of these stores can be depleted within a few minutes of a maximal sprint effort (Gollnick et al, 1973; Fairchild et al., 2003). As a result, active individuals are at increased risks of experiencing a fall in their ability to engage not only in intense aerobic exercise (Ivy, 1991), but also in short sprint effort under situations eliciting fight or flight responses (Balsom et al., 1999; Fournier et al., 2002).”

Fournier et al here point out that even individuals on a mixed diet can experience declines in either intense aerobic or anaerobic (including fight or flight) performance due to glycogen depletion. It is reliably reproducible in experiment, so no one doubts it. I took this as the basis of my argument that human ancestors who did use tubers for starch intake would have had a selective advantage over those who did not, by having superior performance both in hunting related activities and in escape from predators.

Cynthia and David don't believe that glycogen depletes so quickly as claimed by Fournier et al. Let's take a look.

How rapidly does glycogen deplete?

Cynthia and David contend that the statement that close to a third to half of glycogen stores can deplete within a few minutes of a maximal sprint effort is “an exaggeration.” I disagree. Fournier et al make this statement based on research on glycogen depletion in man, some of which Lyle McDonald discusses in his book The Ketogenic Diet: A Complete Guide for the Dieter and Practitioner (Morris Publishing, 1998, pp. 120-123).

McDonald notes that researchers have collected data on glycogen levels under different conditions, including ketogenic diets, which I will now summarize:

• Supercompensated glycogen levels reach 175 mm/kg in trained athletes on high carbohydrate diets.

• Athletes on mixed diets have levels of 110-130 mmol/kg.

• Normal individuals on mixed diets have 80-100 mmol/kg.

• Normal individuals on ketogenic diets and doing no anaerobic training have 70 mmol/kg.

• Exercise performance will be impaired at 40 mmol/kg

• Exhaustion occurs at 15-25 mmol/kg.

• Protein gets converted to fuel during exercise when glycogen falls to 40 mmol/kg or below.

As McDonald points out, researchers in two studies (2, 4) have determined the rate at which glycogen gets consumed during such efforts. At 70% of maximum weight, both studies found a glycogen depletion rate of 0.35 mmol/kg/second of work performed. Translated to seconds:
• 30 second effort, 10 mmol/kg depleted
• 40 second effort, 14 mmol/kg depleted
• 50 second effort, 17 mmol/kg depleted
• 60 second effort, 21 mmol/kg depleted
• 70 second effort, 24 mmol/kg depleted
• 80 second effort, 28 mmol/kg depleted
• 90 second effort, 31 mmol/kg depleted

So, with this data you can see how an intense effort could deplete one-third to one-half of stored glycogen, depending on starting stores. If starting stores are 80 mmol/kg, and you engage in a 90 second lifting effort at 70% of maximum resistance, this will deplete 31 of 80 mmol, or 39% of glycogen, i.e. one-third to one-half.

Can recycled lactate replenish glycogen?

If an individual consumes no carbohydrate following glycogen-depleting exercise, a small amount of glycogen will get resynthesized from lactate. Now for some more numbers (McDonald cites Pascoe and Gladden, 2):

• Production of 1 mmol of glycogen consumes 2 mmol of lactate.

• Only about 20% of the lactate generated during anaerobic activity like weight training (bison lifting) can get converted back to glycogen.

• Lactate levels in muscle during intense anaerobic activity typically reach only 10-15 mmol, with a maximum of 21 mmol.

So, at 2 mmol of lactate per 1 mmol glycogen and an efficiency of only 20%, the lactate recycling would reconstitute only at most 2 mmol/kg of glycogen, an insignificant amount compared to original stores.

Low carbohydrate dieting does not make this process more efficient. One study looked at the rate of resynthesis of glycogen following resistance training absent carbohydrate intake, and found a rate of 1.9 mmol/kg/hr, with a total (maximum) regeneration of 4 mmol/kg (2).

I referred to the following carcass-carting episode as an example of anaerobic activity fueled by glycogen:

“In 1805, the Lewis and Clark expedition witnessed an Indian bison kill ….A small herd was stampeded over a cliff into a deep, broad ravine. As the bison fell one on top of the other, dazed and injured, hunters killed those on top with spears; the others were crushed and suffocated underneath. The ravine was twelve feet wide and eight feet deep; most of the bulls weighed over a ton, yet a team of five Indian hunters pulled nearly all the bison out of the ravine onto level ground for butchering.” (3)

About this Cynthia and David say:

“In the example given of hauling a buffalo carcass out of a ravine, this activity may involve some anaerobic activity, but it will necessarily stretch over an extended period of time and be completed primarily using aerobic metabolism. There may be brief bursts of high intensity effort as needed, and there may even be bursts of extreme effort for particular heavy lifting tasks, but on average the task will necessarily be completed with levels of effort that can be sustained over hours not minutes. We suggest that hauling out a buffalo carcass would not necessarily require a lot of glycogen, and even if it did, would not necessitate gorging on potatoes or other carb food to replenish glycogen stores.”

First, this was not “a” bison carcass, it was a small herd. Next, each bison weighs 1500 or more pounds, the bulls over a ton, and only five men completed the task. The carcasses were hauled out of the ravine intact, for butchering on level ground. If all members of the team participated in lifting each carcass, this means each man had to deadlift and carry up out of a hole at least 300 and at times 400 or more pounds.

Cynthia and David say that this would be completed “primarily using aerobic metabolism.” I see it differently. Let me use a more contemporary example. Although a strength training routine consisting of 15 hard sets of 30-60 seconds each may involve rests of 3-5 minutes between sets, and aerobic metabolism would dominate during the rest periods, I would not say—and I don’t believe any exercise physiologist would argue-- that a strength training routine is “primarily” fueled by aerobic metabolism just because "on average” the level of effort could be sustained “over hours” by the insertion of rest periods.

The activity of interest here consists of lifting bison, not of the rest periods between lifts, and the question is, does this lifting deplete glycogen or not? The answer is, yes it does, regardless of rest between efforts.

Cynthia and David “suggest” that this “would not necessarily require a lot of glycogen…” Let's take a look.

As an experienced lifter, I believe that I can reasonably assume that the men lifting those bison out of the ravine were lifting not more than 70% of their maximum capacity, because they most likely would not have been able to repeat 10 or more such lift-and-haul operations (10 sets of the same movement) in one session if the resistance had been higher than 80% of their maximum.

OK, now let us generously assume the herd consisted of only 10 animals, and moving each animal out of the hole required only 30 seconds of intense effort (doubtful given the task, but roughly equivalent to a 5 to 8 repetition set of deadlifting). The result would be a depletion of 100 mmol/kg of glycogen. That seems like a lot to me, given that normal glycogen stores on a mixed diet amount to not more than 100 mmol/kg, and stores on a ketogenic diet amout to only 70 mmol/kg.

Now above I noted that research has demonstrated that in the absence of post-effort carbohydrate ingestion, lactate recyling only replenishes a maximum of 4 mmol/kg. So you hunt on an empty stomach, fasted for more than 16 hours, which already depletes your glycogen by 50%. Then you help lift 10 bison—your portion amounting to at least 300 pounds--out of a ravine, which would deplete something like 100 mmol/kg of glycogen. You then rely on lactate recycling to “replenish” your stores, and you end up with 4 mmol/kg—way below the exhaustion and impaired performance level. You can see that you will definitely have need for some substrate other than recycled lactate for replenishing glycogen.

Even if I cut the depletion estimate in half, we still have a scenario in which 50 mmol/kg gets depleted, leaving a person with normal stores (due to a mixed diet) at a level of 50 mmol/kg, and a person on a ketogenic diet with only 20 mmol/kg—still below the level of exhaustion. And the lactate recycling still only producees 4 mmol/kg, nowhere near enough to replenish even a third of the original stores.

The need for a substrate

Absent dietary carbohydrate, the only way out of this would consist of converting either endogenous (lean tissue) or exogenous (dietary protein) amino acids into glycogen, at a rate of 1 g protein for each 0.7 g of resulting glycogen. This is where my calculations in Primal Potatoes, part 2, come in.

Cynthia and David state “Glycogen stores can thus be regularly replenished (at least partially- enough to call on in emergencies) as needed even during prolonged aerobic exercise, even when fasting, to support the needs of occasional anaerobic activity.” I did not see anywhere in their discussion any mention of the substrate needed for replenishing glycogen. It does not magically replenish itself out of thin air. Cells have to have glucose to make glycogen, and the glucose has to come from something else: dietary glucose, dietary protein, body protein, or lactate. I just showed that lactate can’t supply enough glycogen to replenish what would get spent in this type of effort. Therefore, the body will use dietary or body protein for the task, in the absence of dietary carbohydrate, because it will replenish glycogen at the expense of muscle mass, since it is definitely more important to be able to run from a predator than to have an abundance of muscle.

Gorging on potatoes?

Cynthia and David say that even if this bison lifting would deplete glycogen, this “would not necessitate gorging on potatoes or other carb food to replenish glycogen stores.” I would like to know where in any post I have advocated “gorging on potatoes or other carb food,” or stated that our ancestors did this?

In my original post, I based all my calculations on replenishing only one-third of maximum glycogen stores (i.e. about 133 g), not on filling glycogen stores to the maximum. I agree with them that keeping the stores somewhat empty has advantages—that is why I calculated for refilling only one-third. To replenish one hundred thirty-three grams of glycogen would require only 133 g of dietary starch, only 532 calories as starch, 26% of a 2000 calorie diet. If gotten entirely from sweet potatoes, you would consume 16 ounces of sweet potato. Since most people consume three to five pounds (48 to 80 ounces) of food daily anyways, I would not classify this as “gorging on potatoes.”

Advantages of dietary carbohydrate

Cynthia and David take issue with my suggested advantages of using tubers. I suggested that consumption of tubers would “Lower dietary protein/meat requirement, reducing the pressure for success in hunting large animals, and making it possible to feed more people (offspring) with each kill.” They seem to think I expressed a “misconception” that eating less carbohydrate means eating more protein, not more fat. Well, besides the fact that eating very little carbohydrate does most certainly increase protein requirements (see below), they missed my point, which is that if you eat tubers, your total requirement for meat (the reason I used “protein/meat”) will reduce because you will now be using a plant food to supply some of your calories and glucose and to dilute protein.

In connection with this, I suggest reading “Energy Source, Protein Metabolism, and Hunter-Gatherer Subsistence Strategies,” in which Speth and Spielman point out that observers recorded recent aboriginal hunters in temperate, subarctic, and arctic habitats having difficulty meeting caloric requirements in late winter and early spring due to the decline in fat stores on ungulants making only lean meat available (5). Very likely Paleolithic hunters had similar difficulties.

Native hunters would at those times abandon a kill consisting of lean meat, despite feeling hungry and having invested considerable energy in the hunt of it, because they knew protein poisoning could occur. If these hunters had a plant source of carbohydrate (or fat), they would not have had to abandon their lean kills, which would have improved the efficiency of their hunting (i.e. less waste). It seems clear to me that this would confer an adaptive advantage. After all, would it not be better not to have to waste hunting effort (energy) on useless meat (because too lean), and would not having enough food confer an advantage over starvation?

Hunter-gatherers certainly thought so—and they weren’t averse to eating carbohydrate instead of fat in lean times. As Speth and Spielman note, “Hunter-gatherer exchange of meat with horticultural populations in return for carbohydrates is documented for many areas of the world” (5).


I also offered that having carbohydrate in the diet would reduce the burden on the liver for ammonia detoxification. They say “this is nonsense.” Well, I happen to believe that the burden on the liver will in fact vary according to the amount of protein consumed. I find it difficult to understand why anyone would call this nonsense. If I make an organ do more work, doesn’t that increase the burden upon it? Let me put it another way: If I make you do more work, doesn’t that increase your burden?

Cynthia and David say “Protein poisoning is just not a serious risk” and state that “protein consumption tends to be self-limiting at levels well below anything that would present any significant burden to the liver.” How then do they explain this report from Randolph B. Marcy in the winter of 1857-1858 , quoted by Speth and Spielman:

“We tried the meat of horse, colt, and mules, all of which were in a starved condition, and of course not very tender, juicy, or nutritious. We consumed the enormous amount of from five to six pounds of this meat per man daily, but continued to grow weak and thin, until, at the expiration of twelve days, we were able to perform but little labor, and were continually craving for fat meat.”(5)

Five to six pounds of meat supplies 560 to 672 g of protein daily, an amount that provides more nitrogen than the liver can convert to urea in a day (6). Since Marcy and his team got weak and thin on it, this illustrates that man can consume protein at levels that can burden the liver. If not so, no one would have ever experienced “rabbit starvation” and protein poisoning as referred to by Stefansson (quoted in Speth and Spielman):

“If you are transferred suddenly from a diet normal in fat to one consisting wholly of rabbit you eat bigger and bigger meals for the first few days until at the end of about a week you are eating in pounds three or four times as much as you were at the beginning of the week. By that time you are showing both signs of starvation and of protein poisoning. You eat numerous meals; you feel hungry at the end of each; you are in discomfort through distention of the stomach with much food and you begin to feel a vague restlessness. Diarrhoea will start in from a week to 10 days and will not be relieved unless you secure fat. Death will result after several weeks” (5)

In short, protein poisoning presents a serious risk, well known to aboriginal hunters, who would abandon lean meat to avoid it, despite having spent an enormous amount of energy hunting it down while starving.


Cynthia and David also claim that my statement that eating tubers would make it easier for a hunter to maintain and increase lean mass in response to the stresses of high intensity activity, with a lower dietary protein requirement, is “False!”

I guess they have never heard of the very well-established protein-sparing effects of dietary carbohydrate. Adding carbohydrate to a carbohydrate-free or very low carbohydrate diet reduces the amount of protein required for maintenance of lean mass, by supplying an alternative source of glucose. Absent dietary glucose, the liver generates glucose for maintaining normal blood glucose levels by gluconeogenesis, which is the conversion of amino acids into glucose. If you supply glucose directly, the liver will reduce gluconeogenesis, which reduces the use and need for dietary protein as a glucose source. This in turn means that the individual can maintain lean mass on less dietary protein. Simply put, the less dietary carbohydrate you ingest, the more protein you must ingest (enough for maintenance of lean mass plus some for generating variable amounts of glucose).

Low carb doesn't work magic

Let me repeat, low carb diets do not work magic. They do not enable the body to create blood glucose or glycogen out of thin air. They do not entirely eliminate the need for glucose, they just shift the individual from use of dietary glucose to endogenously produced glucose generated by gluconeogenesis (the reason for the high blood glucose they find after runs). They do not magically increase the efficiency of recycling of lactate into glycogen. They do not make it possible to consume unlimited calories without gain of body mass. They do not cause body fat to evaporate independent of energy expenditure. They do not eliminate the need to ingest essential micronutrients. They operate under all the same physical and biochemical laws as high carbohydrate diets.

Insulin spikes

On another topic, Cynthia and David state: “And carbohydrate consumption always causes blood insulin levels to spike, which has a whole series of negative consequences.” I don’t know if they have read “An insulin index of foods: The insulin demand generated by 1000 kJ portions of common foods” (7). This project demonstrated that protein-rich foods also cause insulin levels to rise, due to insulin also having a function of clearing amino acids from the blood stream. The insulin scores for beef and fish exceed those for several high carbohydrate foods (white pasta, brown pasta, porridge) and are comparable to others (brown rice, whole grain bread). While in general it is true that limiting carbohydrate reduces insulin responses, I would caution anyone against stating broadly that “carbohydrate consumption always causes blood insulin levels to spike,” without specifying what type of carbohydrate. Since dietary protein also causes release of insulin in amounts comparable to some carbohydrate sources, I suggest taking care not to assert that only carbohydrate causes insulin "spikes."

As another relevant aside, short-term, high intensity exercise also causes a “spike” in blood glucose levels along with an increase of insulin levels to 60 microU/ml, a 2-fold increase over resting values (2). Does this spike have “a whole series of negative consequences”? No. This spike has the function of promoting conversion of blood glucose into glycogen, an essential function for preserving fight or flight capacity. Not all spikes of insulin cause the sky to fall.

Finally, I suggest distinguishing between temporary spikes in insulin, and chronic hyperinsulinemia. The undesired effects of insulin arise from chronic hyperinsulinemia, not temporary rises in insulin levels, so long as those rises quickly subside.

To end, I will quote Speth and Spielman:

“The greater protein-sparing capacity of carbohydrate under conditions of marginal calorie or protein intake may also help to explain why hunter-gatherers in the early Holocene began to invest time and energy cultivating plants, despite the meager returns many of these cultigens
would have provided in their early stages of domestication.”

Not to belabor the obvious, but the Paleolithic lifestyle of hunting big game and tossing any animals with low body fat met up against ecological constraints that made it unsustainable. In response, I suggest that it appears that our ancestors looked for an option, and they discovered that carbohydrate could replace fat as a method of diluting protein, with superior results.


1. Phinney SD. Ketogenic diets and physical performance. Nutrition & Metabolism 2004, 1:2.
2. Pascoe DD and Gladden LB. Muscle glycogen resynthesis after short term, high intensity exercise and resistance exercise. Sports Med (1996) 21:98-118.
3. Eaton SB, Konner M, Shostak M. The Paleolithic Prescription. New York: Harper& Row, 1988.
4. Robergs RA et al. Muscle glycogenolysis during different intensities of weight-resistance exercise. J Appl Physiology (1991) 70:1700-1706.
5. Speth JD and Spielman KA. Energy Source, Protein Metabolism, and Hunter-Gatherer Subsistence Strategies. J Anthro Archaeo 2, 1-31 (1983).
6. Rudman et al, Maximal Rates of Excretion and Synthesis of Urea in Normal and Cirrhotic Subjects, J Clin Invest. 1973 September; 52(9): 2241–2249.
7. Holt SHA, Brand-Miller J, Petocz P. An insulin index of foods: The insulin demand generated by 1000 kJ portions of common foods. Am J Clin Nutr 1997:66:1264-76.


Jonathan said...

Great article. It seems a number of folks have fallen prey to this irrational fear of insulin. Glad to see you helping put things into perspective.

Along those lines, another point worth mentioning is that the Kitavans regularly exhibited high insulin spikes with their high carb diet. But without any hyperinsulinemia, these spikes were always followed by a rapid return to basal levels.

shel said...

fascinating recent posts. you have given me much to think about.

"people eating low carbohydrate diets don’t have the same anaerobic capacity as people eating higher carbohydrate diets (although not necessarily “high” carbohydrate diets) that allow for greater glycogen storage".

i have some questions that might digress from your point. i'm a layman, so might sound a bit naive.

a) do we produce amylase in response to an exploitation of starchy tubers etc., or as a result of a (mostly) nonstarchy omnivorous diet? i ask this because, if i'm not mistaken, fruits, roots and greens have both amylose and amylopectin which must be processed (please correct me if i'm wrong).

b) does amylopectin require processing by amylase?

c) what about energy capture/energy expenditure? granted, man has exploited some starchy tubers (much easier to gather roots than grass seeds), but perhaps overgrazing (overdigging?) would deplete the easily procured surface tubers and force people to dig deeper (much deeper! wow... check out how much work is involved for Australian abos and African nomadics).

d) and finally, because i think this is an important question which must always be kept in mind, is there sufficient evidence to suggest the need for starch consumption for hunting energy (in order to procure energy dense nutrition)? i don't think so. bow hunters in Alberta, whether in the mountains, bush, or on the prairie, don't seem to have a problem; and they usually hunt solo. imagine how easy it is for (most) nomadics, born with bows and spears in hand (and the odd cliff), to work together as a team.

my last question is probably laced with opinion, but i think is valid.

excellent blog. good mind stretching stuff.

Don said...


a) chimps have 2 copies of AMY1, and produce amylase for their diet of 95% fruits and vegetables, but less than humans. So we have a genetic background for producing enough to deal with a diet high in low starch plant foods. the question surrounds our extra copies and 6-8 times as much amylase as chimps.


c) I am not proposing that our ancestors only ate tubers or predominantly tubers, I am suggesting they make a very useful adjunct to a meat-based diet. As for energy return, when meat is so lean it can't be eaten by itself, the energy return for investment is greater for tubers, especially since eating tubers makes it possible to eat the otherwise inedible lean meat.

Tubers are very prolific. Despite harvesting by Aka Pygmies,the permanent wild tuber biomass in their range amounts to 4545 kg (more than 5 tons).

d) yes, in late winter and spring when game is lean, the hunter will need something other than meat in order to meet caloric needs. See Speth and Spielman.

Don said...


Also, I want to make it clear that I acknowledge that hunters CAN live on meat and fat alone, when the game is fat enough. My argument is that using some starchy plants makes it easier and more efficient to live as a hunter, and to produce and support more offspring, especially in lean seasons, so natural selection would favor those who had adaptations to increased use of starch, such as increased amylase. I agree that the bow hunters of Alberta have no problem so long as the game is fat; but when it gets lean, late winter and spring, they do have a difficult time that would be less so, or even not at all so, if they used some starchy tubers like the wapato, ubiquitous in wetlands.

Anonymous said...

wow... that's all i can say. i was the one who originally in your primal potato post disagreed with practically everything you said...

but i must admit, this post "clicked" and it makes sense what you are saying. great post

Jana said...

Congratulations on outstanding research and well-written articles. Keep up the good work!

Drs. Cynthia and David said...

Hi Don,

Thanks for your thoughtful reply and all of the points you raised. I hope you didn't take offense, as such was not intended.

We'll take a closer look at your points and address some of the areas where we think there is ambiguity in terminology and interpretation of the literature. We remain unconvinced by at least some of your arguments and conclusions and believe that the available data are inconsistent and/or subject to multiple interpretations, but we will certainly keep an open mind as we continue digging deeper. These are certainly fascinating topics, and I hope you can keep an open mind as well. Thanks again.

Bryce said...

Many thanks to both Don and Cynthia/David for a fascinating discussion.

Don, you have certainly changed my mind about sweet potatoes. I still avoid starches for much of the week when I'm simply plugging through my day and doing little aerobic activity. However, after a seriously glycogen depleting workout (i.e. 8-12 heavy deadlift singles at 75-80% max) I occasionally enjoy a sweet potato or some brown rice, etc.

I imagine that any people, from the Okinawans to the Kitavans, who frequently ate starchy foods like sweet potatos or brown rice, probably wouldn't have to worry much about chronically high insulin levels. In the near complete absence of refined cereal grains and, worse, refined sugar, it seems unlikely that a normal person could develop any sort of major insulin resistance. Without said resistance, insulin spikes would have simply played their role as important parts of homeostasis.

Am I wrong here?

Thanks again Don for helping me form a more complete picture of the Paleo logic. My wife is certainly happy that I won't be grumbling as much when she serves risoto tomorrow night.

shel said...


yes, when you responded to "d)", the first thing that came to mind was food storage and preservation for late winter/spring. pemmican was a staple and could be stored for years, allowing surpluses to be constantly built up. dried meat/fish and fruit (and "high" meat/fish in more northern climes for early winter) could also be stored.

the starchy tubers thing gets me though. camas bulb and wapato may be ubiquitous; but abundant? not so much in western/central Canada (i can't speak for the US). breadroot, squawroot etc can be found in Western Canada too, but i wonder how much they were used (i know you're not arguing for high amounts, just usage). i'm a hardcore trekker who travels in some untouched country and just don't see this stuff much. lots of cattails (quite palatable), and sloughgrass (not a grain seed, but was dried and ground).

as a curiosity: i make pemmican for my backpacking (50/50 fat/meat per weight). this makes up the bulk of my calories for as much as a couple of weeks at a time. very little carbs are consumed and energy levels are well maintained.

despite my high fat diet, you and Stephan have given me "food" for thought. keep 'em coming.

Sven said...


I really like your articles. I just want to mention two things.

"Let me repeat, low carb diets do not work magic. ... They do not entirely eliminate the need for glucose, they just shift the individual from use of dietary glucose to endogenously produced glucose generated by gluconeogenesis..."

And they shift the individual from use of glucose to fatty acids/ketones. I think it´s important to mention this, while I agree with your other arguments.

Quite often (in paleo context) "run from predators" is mentioned. That always strikes me as a rather naive picture. Do really think you can outrun a predator (lion, wolf, etc.)? A predator will be at your throat quite quickly. Most likely you wouldn´t reach the nearest tree. While glycogen stores might be helpful in your example of the bison hunt, I don´t think that would make any difference in a predator attack.

Don said...


I agree that ketodiets do shift a person to greater use of fatty acids and ketones, but they never eliminate use of glucose entirely.

I take your point about predators like cats and wolves. How about humans, snakes and smaller fauna that also kill? Just thinking out loud, so to speak. Fight or flight would be used to defend your meat from other predators, including other humans. Remember, it is FIGHT or flight. Maybe humans did more fighting than flighting...Masai warriors could subdue lions with nothing but spears.

Bryce said...

Regarding the predator question, and I say this somewhat tongue in cheek, but you wouldn't necessarily have to out run the predator . . . just the guy next to you.

In all seriousness, predators would only catch the slowest person in a group, facilitating the development of the selective evolutionary advantage conferred by anaerobic capacity. If you routinely kill the slowest member of a tribe, you invariably contribute to the collective sprinting ability of the tribe over eons.

Unless we discuss epigenetics, running fast doesn't necessarily mean your children will be able to run faster. But allowing only the fastest to survive would over time increase average speed.

Does that seem reasonable?

To take this further, you could probably swim away from a wolf, or climb away from an alligator . . .

rosenfeltc said...

Your primal potatoes articles have been really interesting to say the least. I have some questions and personal experience problems and was hoping your knowledge and opinion might be able to help me out.

My name is Chris and I've been eating nothing but meat and drinking nothing but water (zerocarbing) for 154 days (a little over 5 months), also I've always been skinny (6'2 165 pounds, basically ectomorph) even prior to go on an all meat adventure so I'm not supposed to be insulin resistant. I can say that this all meat way of eating has helped me for a LOT of things: skin (no more acne used to be moderate/severe), better sleep (no more waking up in the middle of the night, tossing and turning), I only eat two meals a day (I used to eat a lot all the time), it has stabilized my mood(no depression/suicidal thoughts that I used to have on a mixed diet), and probably many other smaller things that I can't think of right now; but It really hasn't helped me when it comes to energy.
During my mixed diet (probably high carb too) I would at least lift 3 times a week plus train 4-6, one hour mixed martial arts sessions a week and I had the energy for all of them. Since switching to an all meat diet, I knew that I would go through ketosis and lack energy for maybe 2 or so months, but after 5 months I'm currently still struggling on weightlifting 3 times a week and have hardly ever energy to go to my mixed martial arts sessions. Some people say it could be tiredness from continuous detox (candida and h pylori from my 2 years of antibiotics use), or improper food assimilation due to my weak digestive system (need to take 20 HCL capsules of 650 mg in order to feel a burn in my stomach), but it could very well also be what you're talking about, I could be depleting my glycogen stores faster than I'm able to refill them for anaerobic exercise whether through ketoneogenesis or glycerol conversion (what is your opinion on this). So now that I've given you a boring summary of my problems, here are some of my questions:

1)I'm assuming your advice would be to consume some amount of carbs in order to refill this glycogen storage. My question is, about how much carbs daily? Is there any other recommended carbs besides the potato that could help? Also it reminds me of the maasai and their virtually all meat diet supplemented with milk (high fat but probably still provided enough carbs), would high fat milk work too? I guess I'm just worried about ingesting carbs that would make my candida and digestion problems worse.

2) I always thought that the flight or fight process was fueled by fatty acids, am I wrong? Which leads me to this point, is it possible that in a ketoadapted individual for him/her to perform anaerobic activity using something other than glucose from glycogen stores (maybe ketones or triglycerides)? Reason I ask is for example if we take this account from Not by Bread Alone by Steffanson when describing the pemmican eaters:
"The men used to row for a space of time, denominated a
pipe, so called from the circumstances of their taking a
smoke at the end of it. Each spell lasted for nearly two hours,
during which time they rowed without intermission. The
smoke usually occupied five or ten minutes, after which they
pulled again for two hours more, and so on."
Rowing seems like a decently strenuous exercise, how could they be able to perform it on a daily basis for so many hours just on pemmican alone (would gluconeogenesis be able to provide enough glycogen?)? There are also more Historical reports of no carbohydrate meat eaters performing pretty incredible feats of human endurance like Sledging in the Arctic for long hours on a daily basis. How was this possible?

Please note that in no way am I trying to show you that your articles are wrong, I am honestly just trying to find the best way of eating that will give me health and good athletic performance. I appreciate you taking the time to read this and please feel free to comment on any of my other issues (candida, digestion, etc...). Thank you

Sven said...


"Fight or flight would be used to defend your meat from other predators, including other humans. Remember, it is FIGHT or flight. Maybe humans did more fighting than flighting..."

That is quite possible. Overall I agree with your argumentation. I just wanted to say something about the "run from the lion"-thing that keeps popping up in different blogs.

Masai warriors could subdue lions with nothing but spears.

Anonymous said...

have you read "the gut feeling on insulin" over at the spark of reason? i think it sums up everything about diet, percents etc very well and understandably.

the only question left is which on is healthiest, maybe not so much for longevity but general all around health

low carb works b/c of the carb cut and insulin is lowered. low fat works because in a round about way you lower insulin levels only because you dont have as much fat to deal with when taking in some carbs. cutting calories works simply because if you limiting yourself, your blood sugar if it runs normally should be cronically high or low.

i can see having a potato now and then as fine, but not if your also eatting a lot of protein and fat the same day. does it make sense if you are going to eat a sweet potato, or tubers in general on a weekly basis to cut you protein down and keep you fat level where it usually is?

also... i dont exactly see the need for tuber in someone who does no exercise, like myself. i have a full tim desk job i sit at for 8 hours a day and am going to school full time at night... lots of sitting and no exercising. theres no need for tubers or carbs even in my day to day life

Don said...


1) I suggest first checking your caloric requirements against intake using Regardless of carb intake, you need to meet your caloric requirements to have adequate energy…which some people find difficult to do on a meat- and fat- only diet. I would guess you need at least 3000 calories daily, so if you only eat twice daily you have to get 1500 at each meal.

2) Masai diet consists primarily of milk and blood, secondarily of meat, not the other way around; this is the most efficient way to live as a pastoralist (Your total caloric harvest from a live cow giving milk is far more than from a dead one). So yes, they get carbohydrate from both milk and blood. Similar to Masai, Fulani live almost entirely on high fat milk and milk products, only eating meat several times a week. Typical Fulani consumes about 137 g carbohydrate daily, about 30-35% of calories (Am J Clin Nutr 2001;74:730–6).

3) I haven't found a way to create a zero carb diet that meets all micronutrient requirements using modern foods. For low carbing, similar to Lutz, I recommend about 75 g of carbs daily as vegetables and fruits, which allows enough vegetable, fruit, and nut intake to meet all micronutrient needs.

4) I highly doubt that 75 g of net carbs daily from vegetables, fruits, and nuts would adversely affect H. pylori or candida. I always use herbal medicines to treat these problems anyways. If these haven't cleared in 5 months of zero carb, I doubt zero carb alone will do it.

5) I don't recommend dairy as a daily food because of its affects on skin (promotes acne), autoimmune issues, and general health.

6) Fight or flight is fueled by ATP/CP and glycogen. The examples you give are NOT anaerobic. You can't carry on anaerobic activity for more than 2 minutes max. Two hours of rowing or sledging for hours uses the aerobic system, and ketodiets do not impair aerobic performance in ketoadapted individuals.

7) Act as if you know what you know. If you can't eat enough meat and fat to meet your caloric needs for the activities you want to pursue, or if you can meat your caloric needs but zero carbing doesn't supply you with the energy you want, you know you had more energy on mixed diet. Add some fruits and vegetables until you get what you want. Don't let an irrational fear rule your life.

For starch, if you want it, I suggest sweet potatoes over potatoes, but either will work. Optimal use involves eating these after glycogen depleting activity, such as strength training, sprinting, HIIT, or intense fighting.

As an aside, others agree with me that people on low carb diet can eat potatoes in moderation. Kwasniewski allows potatoes in his Optimal Diet.


Don, I am wondering about cancer cells being glucose junkies. What does this tell us about insulin in the body in general?

Chef Rachel said...

wow, amazing post! Great work. I like the way you explained things so thoroughly and in terms I think anyone could understand without having extensive knowledge of biochemistry or physiology. I wasn't going to do anything on the computer this evening, then I found I had your page open when I went to shut it down....once I started I didn't want to stop.

Michael said...

As far as protein affecting insulin, it should be noted that while protein does affect insulin, glucagon goes up as well, and it is my understanding that the insulin-glucagon ratio is what is important. Since glucagon rises with insulin when consuming protein and therefore the ratio does not change, it seems to me it is difficult to speak of an insulin "spike" when discussing protein consumption.

Great blog and great post! I'm glad I found it.

Nutrition and Physical Regeneration

Anand Srivastava said...

Thanks Don. This series has been totally incredible. I hope I am not too late to asking some questions. I don't get too often to access net at home.

Just one more question.
Would the glucose be used only in high intensity exercises.

I think that if there is extra glycogen in the liver then the brain would use it. But I don't know why would it do so, if it preferred ketones. Why would stored glycogen be lost for a sedentry individual?

You also showed that the body will only try to replenish glycogen if the level goes too low. Why would a sedentry individual need any glucose at all.

Don said...


Not sure what you are aiming at. Insulin functions to keep blood sugar level within limits.


Even in ketoadapted diet, the brain still uses some glucose, for about 25% of its requirements (75% coming from ketones). This amounts to about 40g glucose required daily, even if bed ridden. This can come from catabolism of amino acids, or directly from glucose/glycogen.

Liver glycogen primarily supplies the brain with glucose. When supplies of glucose get limited, most tissues become insulin resistant so that they take up mostly fatty acids, leaving glucose for the brain.

Fasting can deplete liver glycogen even in sedentary individuals; and some liver glycogen will deplete in service of the brain.

If sedentary, the need for glucose dramatically drops. My speculations are based on intermittent high intensity activity, as required by hunting and gathering.

Anand Srivastava said...

Wow. The brain consumes almost 30% of a persons daily requirement. How does this relate to other animals, do they have similar high requirements. If this is unique to humans then it may someway relate to cooking and access to starch. Thanks Don.

Sanjeev said...

great blog Don.

I hope I'm not thinking that because you think like I do ; )

I'm curious why you don't occasionally do a full carb load.

According to Lyle a strength workout (A Bill Starr or Rippetoe workout, 3 to 5 sets, 5 reps, heavy as you can handle with good form) during a fully carb loaded state is very, very anabolic and exceptional for strength-building.

He has people do that every weekend but that's too much for me.

DonkeyBuster said...

Doesn't dent your premise, but those 5 hunters were probably aided by horses in pulling those bufflers out of the canyon. Not only would the bulls have weighed a lot, but the drag of the ropes over the rim would have added to the effort. Native Americans routinely used horses to aid in butchering buffalo, dragging the carcasses together during big kills, pulling the skins off, etc.

Also, pemmican was made w/berries, another source of carbs. Fat, meat, & fruit pounded together. Winter & traveling food.

Probably all irrelevant here.