Who You Callin’ Stupid and Lazy?

A number of readers have sent me links (thanks, readers) to a new study coming out of the UK that raised some eyebrows all across the Internet earlier this week. The headlines seemed to scream from everywhere “Do High Fat Diets Make Us Stupid and Lazy?” That, in turn, made me scream, so I took a look at this paper in the Federation of American Societies for Experimental Biology: Deterioration of physical performance and cognitive function in rats with short-term high-fat feeding

What I found was a less-than-impressive short-term study on rat performance that told me what I already knew: that it takes a while for new gene expression to really kick in when you radically shift diets. Just like some of you are seeing in the 30-day challenge. So what?

Predictably, this study also prompted the typical editorial “fat kills” reaction from the likes of the New York Times and other bloggers. The ridiculous herd-mentality conclusion reached by almost all of the so-called major media health writers covering this study only serves to solidify my opinion that their heads are so far up their ass-ociation with Conventional Wisdom that they have lost all perspective. In fact, do a Google search for “Do High Fat Diets Make Us Stupid and Lazy” and see how many health publications lifted that sensational headline verbatim. Page and pages. They just took the title from the press release and ran with it.

Here’s what went down. Basically, researchers trained a bunch of rats to memorize a maze in order to receive a sugary treat (the rats, not the researchers…although maybe they got sugary treats, too). Half the rats were also trained to become “proficient in treadmill running” (gotta love that one). Throughout this learning phase, all rats were fed a diet of tasty rat chow that was 7.5% fat, 17.5% protein and 75% carbohydrates. A treadmill runner’s diet if ever there was one.

They then switched half of all the rats from a diet that was 7.5% fat to a diet that was 55% fat (and 29% protein and 16% carbohydrate) and, after giving them four days to acclimate, they tested the high-fat rats against the low-fat rats over the next five days in the maze and on the treadmill and discovered that the high-fat rats were slower negotiating the maze, had memory loss and were less “proficient in treadmill running.” They also found that the muscles of the rats eating the high-fat diet were less able to use oxygen to make the energy needed to exercise, causing their hearts to worker harder – and to increase in size. From this experiment in rat performance, headlines rang out across the world suggesting that high-fat diets make humans “stupid and lazy”. Grok wept.

Of course, the first thing that came to mind for me was, duh, doesn’t everyone know that when you radically shift from a carbohydrate-based diet to a fat-based diet, you can get some pretty wild short-term acclimation issues? The second thought was how stupid and lazy (hey, I’m only using their words) the mainstream media regurgitators are to extrapolate so grossly and irresponsibly from a brief study like this. Maybe I misspoke earlier. Perhaps they had their heads up their assumptions. That’s how public policy starts, folks.

There’s way too much to discuss in depth here, and I suspect a number of my low-carb-blogger pals will weigh in soon (plus we got us a challenge going on here), but a few of my random thoughts regarding holes in the study and questions arising therefrom:

To paraphrase Dr. Michael Eades, rats are not furry little humans and there’s only so far you can go in comparing a 9-day rat study to a human lifetime. This study is a snapshot taken midway through a complex process. I would like to have seen what would have happened if the experiment had continued for a few more weeks. We know that once you shift away from dependence on a very high-carb (high sugar) diet to a low-carb (high fat) diet, you will (at least as a human) experience a number of short-term symptoms or adjustments. Those have been well-documented. Acclimation takes time as new signals from the diet prompt a shift away from glycogen/glucose dependence towards greater fatty acid/ketone reliance. Hormones respond, enzyme systems are increased or decreased, transporter molecules and receptors have to up- or down-regulate. During this acclimation period which may last from two to three weeks, humans will notice loss of memory, fogginess and possibly headaches as the glucose-dependent brain still thinks 100% it’s of energy substrate will be, well, glucose. There will often be a loss of physical energy in general over a period of days as glycogen reserves are gradually depleted while gluconeogenesis ramps up to keep blood glucose stable. Rats probably experience similar discomfort. Of course, once you transition to efficient use of fatty acids as fuel within a few weeks energy, cognition, memory and performance return to normal or improve beyond baseline. Importantly, from the test results it appears that the high fat rats in this study never got into ketosis which might have changed all outcomes (too much carb and protein? The high fat rats were also allowed to consume more than twice the protein grams per day, yet insulin was not measured).

Glycogen depletion promotes short term changes in muscle chemistry and gene expression. This study also looked at UCP3 (Uncoupling Protein3) in the rats’ cardiac and skeletal muscle for signs of inefficient oxidation of energy substrates. No surprise that they found it. Ask your endurance athlete friends what happens to their energy and performance when they switch instantly from a typical high carb diet to a low-carb-high-fat diet. (They don’t know it, but UCP3 up regulates as the body prepares to use more fatty acids.) You’ll discover that they have far less overall energy, that they perform significantly slower and that they run out of steam sooner. They also experience headaches, dizziness and memory loss from the drop in blood sugar. Part of that is because glycogen depletion is a major factor in muscle performance (whether you are on a high- or low carb plan). When muscles are less effective (i.e. when fewer fibers are able to fire due to a drop in glycogen) the heart naturally has to work harder to try to deliver more oxygen to get the chronic cardio work done, hence the enlarged heart in the rats.

But this study didn’t look at muscle or liver glycogen (they said it was too difficult), and only measured blood glucose on the last day of the experiment right after the treadmill run and maze test (RIP, ratons). When they saw equivalent blood glucose levels in high-fat rats, they guessed that liver glycogen had not been depleted and, therefore, was not the cause of the drop in performance. But blood glucose can rise after a workout simply as a result of adrenaline-prompted gluconeogenesis. I forgot to say that these rats got a mild electric shock if they slowed down on the treadmill. Think that might raise adrenaline?

I don’t want to make too much of all this. My point here is that this study only confirms much of what we already know about that midpoint transition in going low-carb. For the media to then extrapolate and say that a high-fat diet makes us stupid and lazy is an insult. Of course, the comment by Dr. Gerald Weissmann, editor-in-chief of the journal doesn’t add to the credibility: “It’s nothing short of a high-fat hangover. A long weekend spent eating hotdogs, French fries, and pizza in Orlando might be a great treat for our taste buds, but they might send our muscles and brains out to lunch.” As my teens used to say, whatever.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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48 thoughts on “Who You Callin’ Stupid and Lazy?”

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  1. I’ve been getting a lot of bad rap from parents and friends that are dietitians for becoming completely primal over the last few weeks. (Although, the one dietitian is a vegetarian, so whatever) Anyway it’s the inability of Americans to think for themselves that creates crappy Conventional Wisdom. They just listen to whatever the media tells them.

    A great book I’m reading is Good Calories, Bad Calories by Gary Taubes. It’s a 400+ page scientific review of case studies and data that proves the Primal diet (high fat, high protein, low starch/sugar/refined grain) is better for heart health and prevention of chronic degenerative diseases. Interesting read if you are skeptical of the Primal diet, or if you need help when explaining why eating Primal is better than the Conventional Wisdom diet.

  2. I guess they should have told the researchers that i’m not a rat,but i sure would eat one, hold the carbs

    1. Exactly! When I read the line, “duh, doesn’t everyone know…” I mentally added “that we are not rats?!”

      As for the headlines, I think it is the ethical duty of reporters–especially those who cover science stories–to favor accuracy over sensationalism. In this respect they have consistently failed us. It is a shame that journalists of Taubes’ caliber seem to be few and far between.

  3. Great rebuttal Mark! Obviously high carb diets make reporters stupid and lazy as none of them bothered to do anything more than repeat an amazing leap in logic from a poorly designed study.

  4. What a moronic “study”. It’s like saying if you lift 10 lbs for a month, then increase your weight by about 500% one day, that you will lift slower and then be very sore for a while. Well no kidding, but that doesn’t mean that it’s bad for you and you should stop (although adding that much weight suddenly isn’t wise). You’ll eventually acclimate to it and be stronger than the other rats out there.
    Who did that study, and I wonder what their agenda is.

  5. “A long weekend spent eating hotdogs, French fries, and pizza in Orlando might be a great treat for our taste buds, but they might send our muscles and brains out to lunch.”

    In other words, high-fat diets may make humans stupid and lazy.


    Well, if that is their idea of a high-fat diet…

    Saying that fat from grass-fed beef, coconut oil, and pastured eggs is the same as fat from hotdogs, french fries and pizza is like saying carbs from an apple are the same as carbs from a slice of wonderbread. 😉

  6. I guess this is pretty much the way it’s gonna be. You can’t compete with the majority, and if you can, chances are you won’t win..

    I wonder.. how come no one brings up the experiments that are pro paleo/low-carb ?

  7. I would post something
    But I can’t remember what
    Too much fat I guess

    I know, the Grokku contest was yesterday, but I couldn’t resist.


  8. Rats adapted to live on scavenged food, usually, grain. There is a reason they are associated with the plague, they were following the grain. I do animal research (they won’t let us take the brains and spinal cords out of people -YET!) Mice and Rats are not people, they’re close but not quite. Journalists ALWAYS get science wrong in the 30 second sound bite, authors given a couple hundred pages have the space to talk about contradictions and falsehoods. I’d like to know why they did so few animals for such a short period of time and who was paying for the study.

    1. I did a quick read through of the scientific article. They were funded through the British Heart Foundation so there wasn’t a corporate agenda, not saying there wasn’t any agenda, just not a corporate one. Still don’t know why they used so few animals, except that the training would be the limiting factor in the study. It would seem to that the treadmill training would equal “chronic cardio” rat version but I can’t be sure on that. Rats don’t run full out for any length of time in the real world. They sprint and stop, sprint and stop.

  9. Here is a link to an interview w/ Dr. Greg Ellis. He has been a proponent of high fat low carb diets for some time. In this interview he makes mention of an experiment done in Sweden w/ high performance athletes. One group given super high carbs for 3 days and the other high fat and then measured how there ability to train was effected on day 7. Of course the high carb dieters performed better because the ones eating high fat had not yet adapted. Anyway an interesting read


  10. grok wept…lol.

    thanks for the debunking Mark…though I am getting pretty good at seeing thru the ridiculous BS now.

    I’m willing to be the weekend in Orlando described by Dr. Gerald Weissmann is pretty darn high in carbs…

  11. I never pay attention to these things…not that I have anything against scientists but they do have to justify their grant funds. Next week wearing rayon boxers will give you prostrate cancer!

  12. I’d also prefer to eat the rat on the high fat diet instead of the high carb one. Haha

  13. Mark – In my view, the problem with extrapolating this study to make any sort of conclusion about human diets isn’t that higher-fat/lower-carb diets take time to adjust to, etc. It’s that rats are made to eat higher carb (grain even!) diets than humans. I wouldn’t be surprised if the negative effects persisted in the rats, given more time, since they were put on a diet they aren’t metabolically designed for. Maybe the study IS correct in helping to illustrate what happens to cognitive and physical functioning with the wrong nutrients!

  14. The basis of the paleo and primal lifestyles stems from the idea that humans have not had nearly enough time to evolve the capacity to digest grains properly (and may never do so if the genes to allow it are not already in place). Rats, on the other hand, have more than likely been eating the seeds of plants for many more millenia than humans. They probably have adapted well to digesting pesky plant grains. This study is rubbish. I spend a lot of time in my biology classes teaching my students to spot pseudo-science like this study and the overreaction by the media to such things. Thanks for responding to the study on your site, Mark.

  15. Way to fight the good fight, Mark. Let me tell you something…I just ran my numbers in Fitday and I’ve been coming in over the last 3 weeks at 56% fat, %15% carbs and 24% protein and I’m anything but stupid and lazy. As a wife, mother and caregiver to my elderly mother AND a business owner, I challenge anyone out there to match what I do and not collapse in a trembling heap when the day is done (or even half over). These people can (inaccurately) extrapolate all they want. I’m living proof their study is pure bunk. It’s just a shame so much of the public will buy into this hooey.

  16. Well maybe Grok didn’t weep. Maybe he selfishly thought, “Cool, let them perpetuate this myth so more people will be inclined to live off cheap filler, leaving more fresh whole foods for me!” Survival of the fittest…let them eat cake…

  17. thanks for this mark. its so refreshing to see others besides myself are getting a smidgen of anger over the myths and lies keeping folks sick and ignorant. when i hear 9y/o kids in our country are getting type II diabetes (my pop is sick with this) it mystifies me that there is so little outrage???um,,,well, ok, just concern?? curiosity??

  18. This study inspired me to conduct my own scientific study. I always suspected chocolate was bad for humans so I fed a box of chocolates to my dog and he got so sick we had to take him to the vet and pump his stomach! My suspicions were correct. From the results of my study I conclude that chocolate consumption is not safe for humans!

    This didn’t really happen but is merely an example to expose what is so wrong with the study; all animals have evolved in different ways to thrive on different types of food. What mice thrive on doesn’t translate to humans or any other animals.

  19. What we are seeing is evolution at work. Natural selection will favour the enlightened few of us that reject conventional wisdom. It might take couple more generations but eventually Grok will rule the world. Wall-E sums up the carb junkies’ fate for me.

  20. On a low carb diet now for 7 months and I just got my labs back and cholesterol is 337 !
    Thought I’d check in with experienced folks and ask for advice and education.
    Could you point me to a several links to help educate me on this issue.
    Here is the link to my labs.
    Is the Cholesterol Myth true for this level?
    Thank you for your time !

    1. The Nurse’s Study found that the women with the HIGHEST cholesterol levels LIVED THE LONGEST!!! Don’t worry about your cholesterol – every cell in your body AND major organs NEEDS it.

  21. The vast majority of nutritional experiments have flaws bigger than the moon, obvious to anyone with just a lay person’s science knowledge. So, how is it with people with PhD’s, medical doctors, grad students are so stupid? Oh, too much fat, I guess.

    I mean, the two flaws that jump out are are rats an ideal animal for a high fat diet, and the duration. DOH!

    Ben, Taubes’ work is mentioned all over MDA, especially the forum. Go to Google Video and, um, google his name, or GCBC. There’s a 70 minute lecture by him that summarizes his huge book.

  22. The fact that the study showed the heart muscle was becoming enlarged is something that may be worth some attention. It’s an indication that the heart is being overworked. My 11 year old nephew died of an enlarged heart, so it is a condition that is life threatening.

    1. Yes, it was enlarged. In a rat. If anyone has evidence of a person on a LC/HF diet dying of an enlarged heart, that would be cause for concern, but I have not heard of such a thing occurring. Rats are primarily herbivores. I could show the exact opposite of this study using a dog or a cat: turns out carnivores are healthy, smart and energetic when fed fatty meat! Shock!

      This same kind of nonsense with rats was used in the 70s to tar the sweetener Saccharin as carcinogenic, when it turned out that the vastly different way rats metabolize sodium than humans was responsible for their cancers.

  23. Also, we can’t do studies on them for obvious reasons, but Neanderthals were the closest species to humans, and they were entirely carnivorous. Various carnivorous cultures (like the Maasai and the Inuit) have been known to exist, and to thrive. Perhaps carnivorous animals would make a better general model of nutrition for species in the Homo genus, then?

    1. Maybe so, but some of us have “evolved” since then. Early man were not just “hunters” but “hunter gatherers,” which implies they also gathered plant foods to eat. We also have teeth that are more adapted to crush and grind plant-like foods than sharply pointed teeth to tear and chew raw meat like a carnivore. So, maybe humans aren’t meant to live on meat alone.

  24. My brother just quoted this study to me this morning. Amazing how fast this information travels and amazing how wrong it goes. My brother just switched to a higher carb diet “for body building”. All he’s built so far is his belly. Typical pot belly and all he’s eating is grains, grains, grains, fruit and yogurt.

    I told my mother about the primal challenge and her response was “All that fat and cholesterol?! Are you trying to kill yourself before your 30th birthday!?” (I’m 28, btw)

  25. I think despite the study being performed by the British Heart Foundation, it was hardly agenda free.

    If you think about the ‘greater good’ then it probably IS much better for the masses to stop eating so much fat! There are two reasons for this, 1. With the problem in obesity, the general population should be eating less of EVERYTHING, and given fat is so calorie dense it is a good thing to go after. We primals think good fat is good. Heart Foundations think fat is bad because most of the fat people consume IS bad! 2, is that we live in a grain-based food economy and that is not about to change any time soon. Imagine taking grains away from China or India or Italy! With that in mind, we will probably see an overall positive effect of studies like this that convince average-obese-joe to consume less fat!

  26. The first question in my head was “What kind of fat was it?” Highly processed vegetable oils, like that rancid soybean oil, will definitely cause a different reaction than nutrient dense saturated animal fats that have so many important nutrients. “High Fat” will cause serious damage if it’s not the best kind of fat. I doubt the rats got anything better than soybean oil or canola oil; and that stuff will make you stupid and lazy.

  27. I wonder if anybody out there knows of George Turner. He ran gyms in California and here in St. Louis area for years. He was a bodybuilder and did a lot of powerlifting and trained a lot of people. He’s in his 80’s now. I started lifting in his gym in 1970. He always preached the high protein diet with LOTS of dark green veggies and big salads. When he was around 70 years old he was in back to back issues in Iron Man magazine. In the pictures he was deadlifting well over 300 lbs. He said his body has still not been touched by a surgeon’s knife. I found a blog by him on the internet from around april of ’09. Now in his 80’s he’s still lifting weights, still eats lean meat and he said he also eats about 25 eggs a week. He said WITH THE YOLKS TOO! Here’s what I say to the authors of all these studies, [email protected](k ’em and feed ’em beans.

    1. You say “…Now in his 80’s he’s still lifting weights, still eats lean meat…” and a lot of salads too?

      LEAN meat and veggies, that doesn’t sound like a high saturated fat diet to me, shouldn’t he be a sick and withering old man if he’s not stuffing himself with saturated fat?

      1. Hey stupid, did you miss the part about about the 25 eggs per week? 😉

        Have you seen his cuts of “lean meat” personally? Often an old timer’s idea of lean is much different than the low-fat generation’s idea of lean.

  28. On the other hand, the fact that so many of the “high fat” advocates are choosing to ignore all the science, could be a testament that the science is right…at least on the “high fat diets make you stupid” part.

    1. On the other other hand, the researchers are smart people simply doing what they are paid to do: bolster the status-quo,

      The really, really stupid ones are those who think that saturated fat consumption is more tightly associated with…health problems than, say, toilet paper use, or sitting in chairs, wearing shoes, or whatever.

      See, the really, really stupid ones are those who can’t seem to define a starting principle, like, say, “hey, we evolved eating meat and natural fats.” So, the really, really stupid ones, for example, will look at a group of CVD victims and point to the meat they eat, not even considering what they wrap it in, bread it with, deep fry it in, or what sweet things they eat it with.

      The really, really stupid ones look at the whole 2+ million years of natural evolution on natural diets and conclude that the way to combat the many modern diseases is to eat less of the ancient foods and more of the modern ones.

      David, you’re not stupid, by any chance?

    2. Actually the “high fat advocates” are picking apart all the studies done by the low fat advocates. If you look at the facts without the manipulation of the low fat spindoctors, they paint a very different picture.