Wednesday, June 25, 2014

Fat and Carbohydrate: Clarifications and Details

The last two posts on fat and carbohydrate were written to answer a few important, but relatively narrow, questions that I feel are particularly pertinent at the moment:
  • Was the US obesity epidemic caused by an increase in calorie intake?
  • Could it have been caused by an increase in carbohydrate intake, independent of the increase in calorie intake?
  • Does an unrestricted high-carbohydrate diet lead to a higher calorie intake and body fatness than an unrestricted high-fat diet, or vice versa?
  • Could the US government's advice to eat a low-fat diet have caused the obesity epidemic by causing a dietary shift toward carbohydrate?
However, those posts left a few loose ends that I'd like to tie up in this post.  Here, I'll lay out my opinions on the relationship between macronutrient intake and obesity in more detail.  I'll give my opinions on the following questions:
  • What dietary macronutrient composition is the least likely to cause obesity over a lifetime?
  • What dietary macronutrient composition is best for a person who is already overweight or obese?
  • Is fat inherently fattening and/or unhealthy?
From the beginning

The first question is: what dietary macronutrient composition favors leanness throughout life?  In other words, if we were able to assign "the average person" to a diet from infancy to old age, what macronutrients would be the least likely to promote obesity?  My answer, of course, is speculation, but there are indirect ways of getting at the question.

Animal studies in a variety of species generally suggest that fat is the most fattening macronutrient, carbohydrate is in the middle, and protein is the least fattening. The ability of fat to cause fat gain seems to depend in large part on its ability increase the calorie density of the diet, suggesting that fat isn't necessarily fattening if it's coming from foods that are lower in calorie density like vegetable dishes and dairy.  Refined carbohydrate is more fattening than unrefined carbohydrate, and presumably the same applies to fat although I've never seen it tested directly.  

Since protein can't reasonably supply the majority of calories in most species, the bulk of calories end up coming from some combination of carbohydrate, fat, and short-chain "fatty acids" produced by the intestinal fermentation of fiber.  The latter are a relatively minor source of calories for humans, who lack the intestinal fermentation capacity of chimpanzees for example, so that leaves us with carbohydrate and fat.  Rodents maintained on unrefined high-carbohydrate diets and without the ability to exercise do gain fat over the course of their lives-- many of them become overweight eventually, and a few become obese.  However, maintaining them on calorie-dense high-fat diets causes them to gain far more fat over the same period of time.  Rodents aren't humans, but the long-term effects of fat-rich diets on body fatness do seem fairly consistent over a number of different species.  

In humans as well, unrestricted diets rich in high-fat foods often lead to a higher intake of calories and higher body fatness than unrestricted diets rich in high-carbohydrate foods, at least in studies lasting weeks (1234567).  

There are countless examples of traditionally-living cultures that remain quite lean throughout life eating diets that are primarily carbohydrate, although there are also a few examples of cultures eating higher-fat diets that are also lean.  It's important to remember that these diets are eaten in a very different context than in the modern world today: abundant physical activity, absence of highly palatable foods, absence of food advertising, etc.  

In my opinion, it's probably possible to design a diet that favors lifelong leanness and centers around either carbohydrate or fat, however it's likely easier to pull off if the diet is more focused on carbohydrate.  If the diet is high in fat, it would have to be carefully planned so it's not too high in calorie density and palatability.  Likewise, the high-carbohydrate diet wouldn't include low-fat Snackwells; rather, sweet potatoes, potatoes, fruit, beans/lentils, oatmeal, and other simple unrefined carbohydrate foods.  

Already overweight

Now, let's consider a different scenario: we're already adults who are overweight or obese, and we want to lose weight and maintain the loss.  What dietary macronutrient composition is best now? 

We have a lot of evidence we can apply to this question.  It's relatively clear at this point that a carbohydrate-restricted diet is a more effective fat loss tool than a fat-restricted diet, at least over periods up to a year.  Some people find that their appetite normalizes and their positive relationship with food is restored by a low-carbohydrate diet.  Typically, on a low-carbohydrate diet, the proportion of fat and protein increase, although in an absolute sense the increase may not be large because total calorie intake declines.  

Overall, these trials suggest that the primary "active ingredient" of low-carbohydrate diets (at least moderate low-carb) is their high protein content.  In other words, high-protein diets yield a similar fat loss outcome whether they're low in carbohydrate or low in fat.  The low-carbohydrate diet concept seems to be a useful heuristic for getting people to eat a more protein-centric diet, dropping some of the junk foods, and getting people to pay more attention to what they're eating.  

Do the results of low-carb diet studies mean overweight people respond in a fundamentally different way to dietary fat than lean people?  Actually, no.  The shorter-term studies show that high-fat foods lead to overeating whether a person is lean, overweight, or obese-- if anything, overweight people overeat more on high-fat diets, and gain more weight (8).  

The difference isn't in the physiology; it's in the intervention.  A low-carbohydrate diet is a restrictive diet, whereas the high-fat diets used in these shorter-term studies aren't restrictive.  They take a normal, unrestricted diet, and shift it to include more fatty foods.  These diets are higher in fat, higher in calorie density, and higher in palatability, without increasing protein intake.  As opposed to the high-fat diet studies, in which people immediately begin eating more calories, when a person is placed on a restrictive low-carbohydrate diet, he immediately begins eating fewer calories.

Health implications of macronutrients

I don't think fat or carbohydrate are inherently unhealthy.  Many cultures have thrived on carbohydrate-rich diets, and although there are fewer examples of cultures eating fat-rich diets, overall they seem to have stayed relatively healthy as well.  Thinking about this from the point of view of evolution, it makes no sense to design a human that can only eat carbohydrate or fat.  Humans evolved in an environment that contained carbohydrate-rich and fat-rich foods, and some weeks our ancestors got more of one than the other.

It is worth noting that the ancestral African hunter-gatherer diet was probably not high in fat on most days, at least not animal fat.  African game is characteristically extremely lean, and the only African hunter-gatherer group I'm aware of that gets a fair amount of fat is the !Kung, and most of that fat comes from mongongo nuts (although the mongongo fruit/nut is mostly carbohydrate by calories, a fact that Staffan Lindeberg recently pointed out to me).  Most African game just doesn't contain much fat, even if you include the brain and marrow, and the primary exceptions, like hippos, are extremely dangerous to hunt with stone-age weapons (9).  I have yet to see a single credible account of an African hunter-gatherer group that regularly eats a diet high in animal fat.  If you know of one, please cite it in the comments.

I've come across a lot of arguments that the ancestral human diet was typically high in fat, but these invariably strike me as wishful thinking.  One argument I frequently encounter is that the plant foods we ate were mostly "fat", due to the fact that the calories they provided were mostly via fatty acids produced by the intestinal fermentation of fiber.  Therefore, we should eat a lot of lard to replicate this.  However, the short-chain "fatty acids" that are produced by intestinal fermentation are not at all analogous to what we normally think of as dietary fat.  These are technically fatty acids, but is vinegar (acetic acid, one of the primary "fatty acid" products of intestinal fermentation) equivalent to lard?  Of course not.  It's completely different on almost every level, from the role it plays in our diet, to the way in which it's absorbed, to the way in which it's metabolized*.

Fat probably has the greatest potential to be fattening among macronutrients, yet it isn't necessarily fattening.  Nuts, avocados, and dairy are probably not very fattening relative to other foods, although it's possible to overeat almost anything.  Lean meat is one of the most slimming foods, despite the fact that most lean meats still contain a fair amount of fat.

In the end, I believe the best diet is the one that keeps you relatively lean and healthy.  That diet might differ based on your background, current lifestyle, genetic makeup, and goals.  A diet's macronutrient composition is one variable that determines body fatness, although it's probably not the most important variable.  It's simply one of the easiest to understand.

* Acetate and butyrate are absorbed by the liver from the portal circulation as they exit the digestive tract.  In the liver, they're used as building blocks to produce glucose and fatty acids.


Mehdi said...

Perhaps, the Maasai folk of Kenya/Tanzania could qualify as a tribe persisting on a high fat diet (high dairy consumption)?

SamAbroad said...

I don't think we can talk about fat or carbs in isolation in terms of fattening diets, but more in 'ratios'.

To whit, I ate some gelato in Rome. The gelato there is typically much higher in fat than store-bought ice-cream. It was exceptionally filling, I could only manage a small scoop, any more would have been sickening. It was very satisfying and I didn't want any more despite it containing not inconsiderable fat and sugar, but the fat to sugar ratio was lower.

I've also found the same experience with mashed potato. If I add butter and sour cream for a much higher ratio of fat, I'll find that I can't really eat that much before becoming uncomfortably full.

This may have something to do with a taste receptor for fat, which it's been purported that some people have, and some don't. I'm lucky enough to have it, other's mileage may vary and they might have to watch their added fat intake more vigilantly.

Richard said...

If we accept the various studies as reality, what I would consider is that the higher fat "diet" is not really about consuming an equal number of calories. The fat itself, as opposed to carbohydrate, produces satiety and, in theory, reduces caloric consumption. With reduced calories comes weight loss, even in the conventional paradigm. The rest of the post makes sense, with the idea that substituting more protein for carb and fat calories will (or at least has the potential to) reduce total calories consumed.

What is only alluded to, in the factors outside of the macronutrients, is the role of hunger, and lack of consumption, in terms of both regular meals and missing macronutrients. In our current western culture people rarely are hungry and are able to fill themselves, and go beyond that, on a regular basis. And with increased carb consumption comes wild swings in blood sugar and desperate feelings of hunger, without any real risk of actual starvation. The body is constantly digesting food, a somewhat unnatural situation.

Jim said...

There are really two kinds of high-carb diets. If it's predominantly starch with little fructose, muscle and liver glycogen get filled proportionally with good insulin sensitivity and little gain in fat mass. But if the diet has enough fructose to encourage excessive liver glycogen synthesis, then there is loss of insulin sensitivity, gain of fat mass and/or diabetes. Surely those with ancestries from places that did not have fruit year-round will be the most susceptible and will be the least well-served by arguments that pit fat against carbohydrates in general.

J Bean said...

The LCHF supporters seem to think that all overeating is driven by hunger. This morning, after breakfast, I was struggling with a computer problem. At least three or four times I got up in frustration and put my hand on the door to the pantry where my husband keeps his junk food stash. Regardless of the amount of fat I had just consumed, I wasn't even slightly hungry. I was frustrated and had made the mistake of setting up my project in view of the kitchen.

The gelato is another great example. Gelato is made from milk rather than cream and churned at a slower speed to make a denser product than ice milk. That little cup of gelato in Rome has less fat than an equal amount of Ben&Jerry's. So why is the little cup, eaten in Rome, while rested and on vacation more satiating than the pint of B&J consumed in fatigue after a trying day at work? Hint: it's not the fat content. It's also not hunger. Why was I jonesing for those boring pretzels? Overeating is much, much more complicated than Gary Taubes' simplistic insulin theory.

raphi said...

Reference 1: margarine, vegetable oil, peanut butter, mayonnaise. Not a suitable design for humans.

Reference 2: "All food items were homogeneous and of a known composition, which was calculated from food tables (32)" --> 32 = McCance and Widdowson’s The Composition of Foods in 1978 ==> ( saying "1.4.8: Fatty acids: For this edition, only total saturated, monosaturated, and polyunsaturated and total trans unsaturated fatty acids are given. More detailed information on individual fatty
acids is available in the Fatty Acids supplement (MAFF, 1998)" = no info on dietary fatty acid composition of the diet or much else.

Reference 3: No access to the actual paper. Also, "This study suggests that endurance runners may not be consuming enough calories on a low fat diet and that increasing dietary fat increased energy consumption" ---> again, calories in affecting calories out. Then "On the low fat diet, essential fatty acids and some minerals (especially zinc) may be too low. A low fat diet could compromise health and performance." ---> not exactly giving the support you've used it for here.

Reference 4: “The composition of foods used to prepare diets was
determined from food tables (7)” —> 7 = Watt BK, Merrill AL. Agricultural handbook no. 8. Washington, DC: US Government Printing Office, 1981. ===> no access to primary material…maybe here ( 1984)? = “SOURCES OF DATA: Nutrient data on nut and seed products were compiled from published and unpublished sources. Scientific and technical literature from the United States and other countries were used as published
sources. Unpublished sources were industry, government agencies, universities, and studies conducted under grant or contract with the Human Nutrition Information Service.” ==> Couldn’t find any information relevant to the nature of food items in the study except a strong suggestion that the fats were those commercially predominant; vegetable oils (mainly).

raphi said...

Reference 5: The appendix lists ==> granola, banana muffin, oatmeal cookies, cheese sandwich, macaroni with tomato sauce, corn muffins, chocolate pudding, chocolate ice-cream, tabouli salad, pasta primavera & so on…highly processed foods containing tons of vegetable oils. Yes, such a HF diet will be bad for you (health & weight-loss wise), surprise surprise??
Following the references further ===> Adams CF. Nutritive value ofAmerican foods. Agriculture handbook no. 456. Washington, DC: USDA Agricultural Research Service, 1975. ===> brings me to ( with this dead-end reference “Agriculture Handbook No 8-1: Composition of Foods--Dairy and Egg Products - LP Posati, ML Orr, Consumer and Food Economics Institute - Agricultural Research Service, USDA, Washington, DC 1976* 144 pp (English)” with no access to relevant primary material. The title however, strongly suggesting vegetable oils as the primary fats used in the study.

Reference 6: Appendix A of the study lists the High-mono diet to include “9g high-oleic safflower oil, 13g safflower oil margarine, 70g egg substitute (??), 109g orange juice, 75g french bread, 56g refrigerator cookie (??), 15g ketchup, 85g banana muffin, 23g dry roasted peanuts” ===> pray tell, what on earth are you expecting to see from this study? Meaningful insight as to macronutrient effects on weight & health? Surely you recognize the massive gaping methodological flaw that feeding humans extruded vegetable oils does not constitute adequate design of a “human-compatible HF diet”…

Reference 7: food composition is from “Watt BK, Merrill AL. Agricultural handbook no. 8. Washington, DC: US Government Printing Office, 1981.” which is to your 1st reference, “Merrill AL, Watt BK. Energy value of foods. Agriculture handbook #74. Washington DC: USDA Agricultural Research Service, 1973.” which does not provide any meaningful insight into assessing the study design, specifically the individual dietary constituents.

So we agree, HF vegetable oil diets suck.
Do you not see the house of cards you’re basing your arguments on? Why ignore the solid HUMAN studies, the metabolomics, the biochemistry?

donheff said...

What you have written largely conforms to my personal experience. I lost 18% of body weight on a carbohydrate restricted diet, and now maintain low weight on a high protein diet with as much unrefined carbohydrates like potatoes as I desire. I continue to avoid almost all sugar and most highly processed carbohydrates. Nevertheless, my maintenance ratio of fat remains "high" because of the moderation on carbohydrate intake. I do not restrict fats at all (presumably because the protein restrains hunger so I naturally limit intake, although, subjectively, the fat seems limit hunger as well).

Conversely, the high fat diets you reference sound like red herrings since they are unrestricted diets in which fat is added to the mix. This sounds like a recipe for disaster under any theory. Don't virtually all recommended "high fat" diets involve simply increasing the ratio of fat as a result of carbohydrate restriction (whether radically, via a ketogenic approach, or moderately - e.g. thru sugar restriction as in my own case)?

The real question in all of this seems to me to be what approach to diet allows us to achieve a homeostasis that naturally maintains healthy weight without constant hunger or the need to count calories.

Wouldn't your conclusions lead a sensible lean young person to restrict sugar and refined carbohydrates, insure a substantial protein component and let the rest take care of itself? And similarly, an overweight person should substantially restrict carbohydrates until desired weight is achieved and then carefully add back complex carbohydrates to the extent needed to achieve a satisfactory, long term palatable, and natural diet that doesn't resume weight gain?

Jesús Bernal said...

Thanks, very helpful

Steve Bates said...

@ Mehdi, the Maasai are a pastoralist group, not a hunter-gatherer one. Most of their kcal are coming from domesticated cattle.

Daniel Bradley said...

Stephan, I'm interested in the topic of fat content in the ancestral diet and I've come across a few counterarguments to the lean African game hypothesis. What do you think of the theory that pre-agricultural humans selectively hunted fattier animals (based on age, species, time of year, etc.)? According to Stefansson, the Eskimo certainly preferred older caribou with more back fat (although obviously cold-climate game is much fattier than tropical game). Closer to the equator, I recall reading that a certain African tribe (perhaps the Hadza?) preferred particular species for their fat even though other species were more numerous in the area. On the other hand, if African game is uniformly lean, how do carnivorous predators like lions consume enough fat to survive? Just curious if you've found any information supporting or refuting these ideas. I agree that certainly ancient humans did not have a fat source to rival domesticated meat and dairy, but I wonder if perhaps leaving it at "African game is lean" sells fat consumption a bit short.

raphi said...

@Daniel Bradley,

SInce we will never 'know' precisely what HGs ate, we might look at the architecture of our cells to clue us in. When one does, it's patently clear that humans can live on high & low-carb diets. The variance in protein intake is much smaller.

We can argue all day about anthropological data but what we can't (or shouldn't) do is ignore the fact that our cellular machinery is perfectly adapted to high fat diets. This cannot be waved away.

The interesting question is: if our cellular machinery indicates humans can run on both high and low-carb diets, what is it about our modern context where health & weight loss are on average "easier" to achieve on lower-carb diets?

Unknown said...

I agree with some (implicit?) ideas:
- eat real natural whole foods
- don't restrict proteins
- avoid refined processed crap (foods made from highly refined ingredients combined to form a very palatable calorie dense item that does not really nourish).

The macro partition from a diet composed of diverse 100% whole natural foods does not matter. The key is natural whole foods as varied as possible (omnivorous is best in that respect).

Keith Hansen said...


In your talk "Why Do We Overeat? A Neurobiological Perspective" you describe the mechanism responsible for "permanent" fat gain--the bodies decreased sensitivity to leptin.

Is this decreased sensitivity due to inflammation caused by diet?

If so, what is responsible for this inflammation?

What is the mechanism that allows lowering of the body fat mass setpoint?

Jim langley said...

Good read!

Unknown said...

There's some evidence that the satiety increasing benefits of dietary protein arise from hypothalamic mTOR activation, particularly by leucine and other BCAAs.

Those who follow experimental gerontology will note that this is not without possible long-term adverse consequences, as mTOR activation tends to speed aging, while inhibition is common to virtually all anti-aging interventions.

Mike said...

This parallels what I have read about the plains natives who preferentially hunted the bison in late summer and fall when the animals were both fatter and the fat was a higher % saturated more stable for making pemmican.

Obviously, they had no direct concept of "saturation", but through generations of experience understood that the fat taken from animals later in the year was much more stable and provided a long shelf life for the pemmican.

OldTech said...

Stephan, thanks for a well rounded overview of where the evidence points. While I have been thinking that too many carbs is a potential reason why I have type II diabetes, it now clear to me that there are some other potential triggers. Carb composition is one. Fat composition is another one. And still another is gut health. I am sure you can think of others.

I started a few months ago with the view that carbs were evil based on the fact that I am very carb intolerant. However, I am now trying potato RS (day 17) and so far finding that it is significantly improving my gut health. I also have my fingers crossed that RS will also improve my carb intolerance. Perhaps I can even bootstrap my way into eating more natural sources of RS. Ymm... sushi.

MacSmiley said...

I was frustrated and had made the mistake of setting up my project in view of the kitchen.

Maybe the real mistake is the existence of the junk food stash? ;-P

Teech said...

I also forgot to mention Stephan posting about how in the 1800s we consumed around 13 lbs of sugar a year and today we are over 100 lbs a year. For some reason, sugar has taken off and is replacing other more nutritive macro nutrients. So even if fat is more fattening, Americans have replaced the missing calories with sugar and the extra ones as well with sugar.

Morris said...

My experience is very different from both Dr. Guyenet’s and from paleo advocates’ explanations. I will not try to explain as I don’t believe people are really interested but I will mention some relevant (in my view) observations. My problem was not overweight ;BMI 24 at start, 23, 4-1/2 years later, but significantly less body fat. I kept an accurate record of dietary intake (daily record, food weight measurements for one year) and varied calories slowly in a range of 2:1 (1000-3400kcal). Changes in apparent health (as indicated by aging markers) were very slow and fluctuating but with a positive trend. After 4-1/2 years my current calorie intake is a little less the trial minimum ( at which level I did not feel well) but my weight is stable and in fact I have gained some lean body weight. In effect I am on a calorie restricted diet with >50% cal from fat but without any dieting effort, my appetite is completely self-regulating. So I either I am a mutant (no other reasons to support that) or the proposed explanations are incomplete. After 1-1/2 years of my experiment and good results I asked Dr. Guyenet on this blog what to make of my contrarian results and he said essentially get back to me in 20 years and then see. My experiment required a fair bit of work and study so I doubt that this approach is at all practical. Nothing in my experience contradicts microbiology or immunology textbooks. I strongly suspect that there will be no responses to this comment. My experience suggests that there exists a stable ‘just-so’ state where metabolism self regulates but that this state is very narrow and not easily attained once you are outside of it. This would not be surprising for dynamic inanimate systems so maybe even less so for living/evolving organisms.

Joe M said...

I think looking at contemporary game animals as a sufficient benchmark of leaness or fattiness of game meat for our ancient ancestors is faulty. The game animals found in East Africa today are a significantly reduced subset of the fauna found during the pleistocene. Evironmental degradation, isolation of populations, rising temperatures with non-anthropromoric global warming, and human hunting pressures have lead to a dramatic decrease in size of available game. This includes the loss of megafauna and the general trend for animal prey size decreases in size during intense hunting pressure.

We know our ancestors hunted megafauna when available, only shifted to more small game when the megafauna disappeared. This is important because larger animals generally carry higher percentage of body fat than smaller animals. Very large animals can be more easily selectively butchers to maximized caloric density to offset the carrying and processing costs. In addition larger animals have larger bones, and their bones are larger in proportion to their overall size. Large animals need more structural support. A mouse scaled to the size of an elephant could not more without injury. Larger bones require larger diameters, and volume scales must faster than diameter. Therefore the amount of bone marrow in a mastodom leg is probably 100 times more than a Thompson Gazelle or Wilderbeast's leg.

Selectively harvesting fatter prey animals and preferentially taking tongue, liver, lungs, brain and marrow from megafauna would dramatically increase the percentage of animal fat in the diet compared to eating a whole antelope from snout to tail.

Stephan Guyenet said...

Hi All,

Sorry for the delay in posting comments; I wasn't able to find time to moderate last weekend.

Regarding the fat content of wild game, it's certainly true that hunter-gatherers target the fattest prey they can get, and that has probably always been true. Humans have a hard-wired motivation to seek fat. In some places, like arctic and some temperate areas, there would undoubtedly have been abundant animal fat during certain seasons (in some arctic areas throughout the year).

However, African game tends to be very lean, and it probably has always been very lean. Leanness is just a general characteristic of tropical game. Our closest relatives the chimpanzees only have about 3% body fat in the wild.

There are a few exceptions, such as hippos, but my impression is that it's uncommon for African HGs to get their hands on fatty game.

We can draw an analogy with sugar. Humans have a hard-wired motivation to seek sugar, and honey is the most concentrated source in the wild. We like honey and we seek it, but the amount HGs can get is limited, when averaged over the year (although there may be more honey available than animal fat).

In the case of both sugar and concentrated fat, we're driven to seek it but there isn't enough of it available in Africa for HGs to indulge to their hearts' content.

As I mentioned before, I have yet to see any credible account of an African HG group that eats a diet high in animal fat. We can speculate about what ancestral African HGs ate and how they feasted on animal fat, but there's not a shred of evidence to support those speculations (we have no idea how much animal food they ate, we only know that they ate it), and the fact that tropical game tends to be lean makes me doubt the likelihood of it.

C. Clemmensen said...

Have you seen this article Stephan, maybe not 100% relevant in context, yet somewhat interesting:

Daniel Bradley said...


I've heard the claim that glucose is the primary fuel at the cellular level, and I've also heard the rebuttal that glucose is simply burned first, and then fat is burned as the preferred fuel source. I've never seen a citation for the fact that fat is preferred -- since you claim to know something about cellular machinery, are you familiar with any sources on this matter? I'd also be interested in any sources for the claim that dietary carbohydrates are converted to saturated fat past a certain threshold. These are quite reasonable-sounding things I've read in many places but for which I've never seen a good reference.

I agree it seems odd that humans, as omnivores, would be maladapted to any reasonable mix of carbs and fat as fuel.

Galina L. said...

probably , it was also more practical to try to preserve "the fat taken from animals later in the year" when temperatures were low, than to deal with the challenges high temperatures present during summer.
I found it funny that the pemmican preparation sort-of mimicked the situation with other preservation activities, like a sauerkraut making in traditional societies is usually done only when summer is over - the early summer cabbage is too soft when fermented, a fermentation during warm weather will result in a bitter tasting cabbage.

Richard said...


I think my post and situation is not too different: I have been consuming more saturated fat and less carbohydrate for the last 4+ years. More protein and no wheat. The result was an initial dramatic weight loss, followed by regaining weight, most of it muscle. Of course, the only thing I'm "religious" about (beyond diet) is exercise, which for me means tennis and weight-lifting (an odd mix, I guess). I think I'm on a Paleo diet. And I'm 69 now. My other thought is that the low carb diet is much less stressful on the insulin producing cells, particularly if Intermittent fasting is one aspect of all this.

Stephan Guyenet said...

Hi Christoffer,

I'm aware of that paper but I haven't read it yet.

Hi Daniel,

I'm wary of words like "preferred" that imply a value judgment.

The body oxidizes fuels in a hierarchy based on its storage capacity for each. Ethanol is burned before (excess) amino acids, which are burned before carbohydrate, which is burned before fat. The body can't store ethanol and can scarcely store excess amino acids so it has to burn them right away. It can store some carbohydrate, so that's next. It can store huge amounts of fat, so fat mostly gets burned by default when other fuels are unavailable. But the body is always burning some mix of amino acids, carbohydrate, and protein; the mix is simply shifted based on what's available. Insulin is critical in coordinating the shift.

The point is that glucose is mostly burned before fat, but that doesn't imply anything about how healthy it is to run your engine on glucose vs. fat.

Grinch said...

I just wish people would stop arguing over whether its fat or carbohydrate that is causing the obesity epidemic. There seems to be an overwhelming amount of evidence showing neither one in isolation can be the cause. It seems like it requires the combination of the two, but its more due to coincidence. All of the most palatable foods I can think of are high in both carbs and fat. I think its palatability and caloric density that matter as Stephan has been writing about for years. I think the diversity of the food is what makes it palatable to us, and we just have too much of the stuff available and all the aspects of the food that provide satiety have been stripped out.

What I'd like to know is how exactly does food reward / palatability interfere with leptin. How powerful is leptin verses food reward? Anecdotally I feel an overwhelming desire to overeat junk food when I eat light for the day or workout, is that because of leptin or food reward, or what other hormones? I've read that leptin is a long-term hormone, so why do I get so hungry when I'm in a short term calorie deficit? Does food reward respond to calorie deficits or is that leptin and grehlin perhaps? That's where I want to see the arguments narrow in on.

raphi said...

@Daniel Bradley

I agree with Stephan's description of fuel usage.

If you are looking for information supporting why I say that our cellular architecture is well set-up for fat burning (B-oxidation) then I suggest Molecular Biology of the Cell, 5th edition + Peter@Hyperlipid's blog & this very technical talk (if you're up to it) . Here you will find some help with terminology & basic understanding of what's-what. Hope that helps!

Scott Sterling said...

I would be interested in hearing from commenters and Stephan if you think the following statement would be accurate and would greatly simplify this very complex subject:

"Almost no one would have a weight or hunger problem if...
-You eat real food only, with any mix of macronutrients
-You get on a proper sleep cycle
-And you regularly commune with other humans."


David L said...

Here are two alleged scenarios where eating a high protein/minimal fat diet has led to body wasting and even death:

1) Into the Wild tells a story of an isolated camper who dies after feeding only on lean game. The result is that his body weight diminishes to the point that he is a skeleton. However, there was plant poisoning also going on, so the inference can't be total.

2) The Donner Party. They began to live off of dead individuals who had minimal fat. The remaining living individuals also died of being too lean.

Your thoughts?

David L said...

Good Fats/Bad Fats


In a lot of earlier posts, there seemed to be a positive spin on animal fat: fat-soluble vitamin; Vitamin K2; eating organ meat, especially liver; and the benefits of whole and/or non-homogenized milk, for example. You definitely seemed to prefer animal fats to those from industrial seed oils.

Is fat still good, the right type, but in moderation, or have you revised your earlier positions?

Honey Razwell said...

Hi Grinch and Scott Sterling :

I will try to answer. :)

I think that, in general, the Blogosphere ( * this does NOT apply to Stephan)is asking the wrong questions. We have to ask the right questions, in science, as Isaac Newton said.

Contrary to what is often said, testable , predictive theories did NOT lead to progress, nor the Scientific Revolution. Any crank can say the sun will burn out next Tuesday and has a testable idea.

Being shown wrong by observation and experiment and changing your theory accordingly STILL will not get somebody one jot closer to understanding a given phenomena if certain criteria is not present. This did not open the intellectual prison gates either.... It does not even matter of something is testable if certain criteria is not present. I will expound on that later. yes, testability is necessary, HOWEVER, it is not nearly sufficient. It's not good enough.

Genetic studies have shown that the particular set of weight-regulating genes that a person has is by far the most important factor in determining how much that person will weigh. None of this "contradicts the first law of thermodynamics" in any way, shape or form, as so many Bloggers erroneously claim based on their faulty understanding. It is more appropriate for a naturally thin person to thank their thin genes than to stigmatize the obese.I have confirmed this with about 40 different scientists from places like M.I.T., CalTech, Harvard and Cambridge over the last 6 years.

Science is about figuring out how we are wrong. Most amateurs dramatically overstate science. Science has strength and it is wonderful. BUT, science has flaws and weaknesses- like all human creations and endeavors.We need humility. We should not assume we know everything. For instance, here is an example of the limitations of science : There may have been very, very important observables 5 billion years ago that we missed. We may be forever limited in what we can even know and the questions we can even ask because of this.

I think the Blogosphere MUST get out of the mindset of asking "What cheese the Moon is made of." My own 1998 beliefs and misconceptions about obesity were challenged over the last 6 years. I now realize that I was wrong and have forced my views to conform with evidence from reality no matter how painful.This is what Saul Perlmutter stresses. I think we need to channel Einstein and get very creative. We need to think about this problem like we have never seen it before to some degree. Feynman and Einstein both recommended this approach top science and you can use it in various disciplines.

What is taught in science textbooks in 6th grade is pure unadulterated nonsense and not how scientists conduct their work. There is no such thing as "The Scientific Method." This phrase is an insult to scientists everywhere. it is a disgrace and a travesty and inaccurate. Scientists use literally thousands of methods and they are all different. It is the greatest most persistent myth around. Science textbook writers and the Blogosphere are the most egregious promoters of science myths and misinformation.

What we need is a much deeper understanding of obesity at the molecular level.

Daniel Bradley said...


Thanks for the responses. You're right, preferential isn't really a good term to use here. What an interesting topic.


I'll check out those links, thanks!

Sergio said...

Hi Stefan,

"The body oxidizes fuels in a hierarchy based on its storage capacity for each. Ethanol is burned before (excess) amino acids, which are burned before carbohydrate, which is burned before fat. The body can't store ethanol and can scarcely store excess amino acids so it has to burn them right away. It can store some carbohydrate, so that's next."

I think I understand the carb storing part, please correct me if Im wrong.
Muscle glycogen (max ~400gr) depletes with certain type of exercises and cannot exit the muscles. Liver glycogen (max ~90gr) goes down automatically even sleeping. If we ingest glucose and our storage capacity is already used, we mostly turn that glucose into palmitic acid instead of storing it (muscle glycogen repletion is somewhat slow though). If we eat fructose and the liver is "empty", only up to ~50% the fructose can turn into liver glycogen.

Is there an analogous story for "excess amino acids"? What does it mean "excess amino acids"?

admin said...


I know that this might be off topic somewhat, but I have a question about bodybuilding nutrition. From what I have seen/read on the internet a physique athlete would want to have high protein/carbs and low fat intake. With taking in thousands of calories why would having a lower fat approach be beneficial in this situation?

Grinch said...


Have you seen the latest saying exercise is more important than calorie intake? I highly doubt the conclusions here.

Methinks said...

I have the answer! Our obesity epidemic is caused by fat emulsified with sugar!

Though that's probably true to some extent, I'm kidding, of course.

Despite being an athlete and carefully watching my intake of complex and "healthy" carbs, my energy levels were crazy and I began gaining fat in middle age. And IBS was getting worse. Out of sheer desperation I switched to Low carb and very high fat. The fat fell off and everything else resolved.

My cousin has PCOS and despite a strict calorie restricted diet she kept gaining weight until she changed her diet to resemble mine. Of course, our ancestral home is very far Northern Europe, so that may play a role.

This is what works for us. It seems natural and pain-free for us. It's probably not for everyone.

One thing that I wonder about is this idea that there's one cause of obesity. How much variance is there in the human population? Wouldn't a high variance make standardizing dietary recommendations moot?

Stephan Guyenet said...

Hi Grinch,

Yes I saw it. It's based on NHANES self-reported calorie intake. There was another recent paper about how abysmally inaccurate NHANES data are for estimating calorie intake. Self-reported data are particularly bad for answering this type of question because heavier people tend to under-report calorie intake to a greater degree. That means the more obese the population becomes, the more people will tend to underestimate their calorie intake.

USDA estimates of calorie intake, which are not self-reported, suggest that calorie intake has closely paralleled the prevalence of obesity.

Hi Methinks,

Congratulations for finding an approach that works so well for you. I agree that there is probably a lot of variability in what works between different people, but there are some things that are more likely to work than others.

Stephan Guyenet said...

By the way, this diet vs. exercise debate is a perennial way for the news media to keep us watching. Personally I think it's extremely obvious that we're more sedentary than we were 100 years ago (though not necessarily 20 years ago), and we also eat more.

Both factors probably play some role, but for me in the end it comes back to calorie intake, and here's why. Calorie intake is supposed to be unconsciously regulated by the brain to match calorie intake to calorie needs. The more active you are, the more your appetite increases, and the less active you are, the more your appetite decreases. You can eat too little or too much at any given level of activity. The problem is when your calorie intake exceeds your calorie needs.

The key question is, "why do we eat more calories than we need"? Physical inactivity may play some role in that, but it's definitely not the whole story.

Unknown said...

Hi Stephan,

These two statements seem to contradict each other:

"Calorie intake is supposed to be unconsciously regulated by the brain to match calorie intake to calorie needs. The more active you are, the more your appetite increases, and the less active you are, the more your appetite decreases."


"The key question is, "why do we eat more calories than we need"? Physical inactivity may play some role in that, but it's definitely not the whole story."

This unconscious mechanism that you are mentioning must be broken in sedentary people if physical inactivity makes them eat MORE, because from the first statement, if one leads a sedentary lifestyle, the appetite should in principle be down-regulated, shouldn't it ?

Stephan Guyenet said...

Hi Unknown,

It's a difficult concept for me to explain in a short comment, but the key phrase is "supposed to be". We have a system that's supposed to match calorie intake with calorie expenditure, or at least get it in the ballpark, but in the current environment that system is overridden and/or altered by environmental factors.

Inactivity doesn't make people eat more, but there is some evidence that it does reduce the ability of the brain to appropriately match intake to expenditure (such that a sedentary person might have a tendency to eat more than his needs, but not necessarily more than an active person in an absolute sense). In other words, physical activity maintains the brain systems that appropriately regulate appetite.

raphi said...

So, something like bad diet for e.g. can affect brain activity & levels of physical activity also, no?

Joe M said...

Yes animals in the tropical regions are on the leanest end of the fat contant spectrum, but that leaness is variable between individuals, species and regions. The same type of game animals in southern Africa carry more fat than the tropical varieties. In addition, the hypo amount of fat is not that much of an outliner compared to other big body mammals like elephant and cape buffalo.

It is well documented in Africa and in Yellowstone Park that when large keystone species like elephants and gray wolves are removed that ecosystems are dramatically changed. With the loss of wolves, coyotes and elk populations exploded in Yellowstone and the fauna and flora community had dramatic reactions. If you or I don't know the exact animal or plant community composition of Africa 50,000-250,000 years ago, then we can't just assume is it like is today. Today ungulates are common as African game, but that wouldn't have supported the much larger Dire Wolf, sabre tooth cats, cave lions that did in fact exist. Megafauna made the everthing different.

I am not saying our African ancestors ate like Intuits, but the much higher body mass prey they had access then had more fat than modern prey animals that survived the megafauna die off.

Archie said...

There is clearly a lot of variety in human metabolism. Some folks thrive on high carbs - is there any evidence that those healthy carb eaters seem to cluster in ethnicities with deep agricultural roots (think Mediterraneans with wheat or East Asians with rice)?

I believe there is strong evidence for alcoholism being correlated with short time depth of agriculture, that would seem to explain why aboriginal peoples have such trouble with alcohol. The alcoholism prevalence within Europe would seem to mirror this effect, with late-to-farming regions in the far north (Irish, Scandinavians) having greater rates than the southern countries. Would long term farming also drive a population's ability to eat grains etc. without too much trouble? I believe the AMY1 gene repeat number has been shown to correlate with farming depth. Perhaps you could opine on this subject?

Jack LaBear said...

@ Morris

I had a similar experience. 15 years ago in my early 40s, I was getting pudgy, health and brain function were going downhill and I had problems like hypoglycemia and bloating/urgent and loose stools. I eliminated most grains, lowered carbs to about 100g/day and upped the fat. I eat mostly real food. All the symptoms resolved and my body fat % dropped to around 10% now. TC fell to 120mg/dl.
I restored my metabolic flexibility. Because I get most of my calories from fat, my body is in fat burning mode most of the time. If I skip a meal or two, hunger is minimal and no hypoglycemia. Since I have a sedentary job, I spontaneously eat about 2000 cal/day.
I do 14 sets of strength training every 5 days, and at 57, I'm BMI 25 and <10% BF.
Folks can bash LCHF and refute Taubes till they're blue in the face, but 'paleo' is popular because it works long term while making folks look, perform and feel better.

karl said...

You bring out a point that is central to this debate. The so-called-fats in the so-called High-Fat-diets in MOST of the rodent studies are not what their headlines claim them to be.

The typical anti-fat study uses hydrogenated vegetable oils and even sugar as the straw-man.

Any paper that uses any combination of: hydrogenated oils(nice for shelf life),sugar, increased carbohydrates and calls this a 'highfat' or "Atkins diet" is and fails to figure changes in O-6 is worse than noise.

If peer review was working properly these papers would be rejected and should now be retracted.

At some point the "everyone does it" excuse needs to go.

I think there is good evidence that O-6 (and perhaps polys in general), trans fats (hydorgenated) are not 'natural human foods' and have serious adverse health effects. Purposefully confounding these, omitting the information from papers becomes politics and is no longer science.

Stephan Guyenet said...

Hi Karl,

There is no compelling evidence that n6 or trans fats are more fattening than other types of fats. Rodents will get plenty fat on regular butter and lard, and most modern high-fat rodent diets are made primarily with non-hydrogenated lard. The most commonly used fattening rodent diet doesn't contain much sugar, and in any case sugar itself isn't particularly fattening in rodents to begin with. The best fattening effect is achieved when high fat and low-moderate sugar are combined.

Dietary fat tends to be fattening in rodents, and in certain contexts it can be fattening in humans as well. I don't understand why that is so hard to accept.

Bruce W. Perry said...

I'm not sure if this is pertinent or not, but I live in an area where an above-average number of people hunt for food (Vermont). They'll take a bear under a license, then eat the whole bear throughout the winter. This is a wild animal, and very fatty.

So are smaller plant-eating animals that have thick or coarse hides and lots of subcutaneous fat. I think if you studied an African hunter's diet, you would find a lot of fat in a hunted animal's flesh. They capture small burrowing, fatty animals. They will eat the liver and the heart (including those VT hunters), both of which can contain regions of high fat. Muscle contains far more calories in the form of fats than glycogen (smart evolution: fat is a greater energy source for the muscle), including human muscle. A wild animal, including "lean" meat, contains more fat than meets the eye.

We also evolved from Northern Europeans tens of thousands of years ago, who ate a lot of fatty, cold-weather animals.