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Athletes Consuming Ketogenic Diets Have The Fuel Reserves To Handily Outperform Those Following Typical High-Carb Diets

When Martians Attack Carbo-loading Could Spell Your Doom!

Athletes Consuming Ketogenic Diets Have the Fuel Reserves to Handily Outperform Those Following Typical High-Carb Diets

If you are on a ketogenic diet (50gm carb per day or less), your metabolism is adept at burning fat for energy and so your energy reserves are only limited by they amount of body fat you have. This means, if you are a 150 lb man with 20% body fat, you could (assuming you replenish all the electrolytes, fluids, etc., and that your joints hold up) burn through 49,000 kcals before you hit “the wall.”

This is in comparison to the measly 2000 kcals you have access to (from muscle glycogen) if you are not keto-adapted and follow a typical, high-carb diet including carbo-loading the night before a big event.

Low-carb Versus High-carb: Competitive Running

Luke is always reminding me that information like this is more interesting when I include a practical application. So here it is: If you are an endurance athlete on an old-fashioned high-carb diet, sometimes still recommended by fitness magazines that endorse carbo-loading, you can expect to hit the wall at around the 20 mile mark of a 26-mile marathon.

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If you train on a low-carb diet and skip carbo-loading altogether, you have access to a much larger supply of caloric reserve (from body fat) and stand a good chance of blowing by your competition as their gas tanks run empty.

Low-carb Versus High-carb: Running for Your Life

But here’s how this applies to the majority of us who aren’t extreme ultra-athletes. A recent article in The Guardian explained that NASA is concerned that global warming may alert space aliens to our presence in the galaxy. Sensing us as a threat, NASA warns, the aliens may be forced to attack.

If you’ve ever seen War of the Worlds, or any alien-attack movie, you already know how this imminent threat is destined to play out. As soon as the invaders finish hovering around making ominous cloud formations, they get right to the business of blowing stuff up. It’s at this point that all the Earthlings will be forced to grab their kids and sprint down the street, Tom Cruise-like, as cars and pieces of houses and bridges fly through the air in the background. This running part, you’ll remember from the movies, can go on nonstop for days. And since all the restaurants are gone and grocery stores destroyed, there’s nothing to eat.

Ketogenesis and Survival

This is where the true benefit of the ketogenic diet will manifest. If you are not dependent upon regular infusions of carbs for energy, you’ll be able to keep on running ahead of the space aliens’ plasma blasts long enough for them to succumb to an Earth-born virus (or a virus Jeff Goldblum has downloaded into their computer mainframe, whichever comes first).

Not only will you and your family survive the aliens’ onslaught, since you will have been burning fat and working your muscles all week, you’ll look fantastic. When they vote for which groups of people should be charged with the duty of repopulating the Earth, you’ll be placed at the front of the line.

Although NASA specialists didn’t mention this, it’s entirely possible that benevolent aliens, sensing our distress, could show up offering gift baskets filled with cherry tarts, muffin-tops and all manner of high carb treats. In this case, low-carbers would risk offending the sensitive aliens by turning the gift baskets down.

Whichever way it goes down, there’s always the athletic performance thing.

With over two decades of clinical experience and expertise in genetic and biochemical research, Dr. Cate can help you to reverse metabolic disease and reshape your body.

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This Post Has 27 Comments

  1. Dr. Cate,

    I came across this article when searching for information on training for a marathon. I’ve been following your recommended diet (4 pillars) since last October and feel great. I’m training for a marathon now, and definitely notice having a larger store of energy during my runs. But every single training plan I read recommends refueling during the long runs and during the race itself. Generally, these running foods are pure sugar of some sort (I used to make mine with a combination of molasses and honey).

    Would you recommend refueling during a long (2.5-3.5 hr ) run? If so, would you recommend doing so with something more protein and fat? Or is this a situation where a dose of sugar is what my body needs?


    1. Ben Greenfield ( discusses using a slow-releasing form of sugar to boost performance during competition, not training. He uses a brand of something called UCANN (, but I any starchy food that is slow to digest, like sprouted grain bread, would have a similar benefit. So sorry for the long delay in replying to you! My excuse is that my website was having a lot of issues and some comments were impossible to find!!!

  2. Theres alot of research showing the benefits of interval training. At the American College of Sports Medicine meeting in Denver last spring, I attended quite a few excellent lectures on the subject. Of course, its been a topic of research for at least the past decade and we discuss this in Chapter 10, in our exercize section.

  3. Hi Dr. Cate, browsing Amazon today I saw a new book that I hope you review when it comes out. It’s called Unlock Your Muscle Gene by Ori Hofmekler. From the table of contents it looks like he’s tackling a lot of similar topics as you do, what foods encourage muscle growth, proteins vs. carbs, meal content, etc. Also, relevant to that, and your TRIM program, I’ve been hoping to hear more from you about exercise. Specifically, if you think there’s a style or frequency that you think works best. Thanks for your great advice and for shaking up your fellow medical colleagues!

  4. I love this your latest hilarious ponderings. Deep Nutrition is one of the most influential books I have ever read….am a huge fan of Fibonacchi! Recently diagnosed with Type II diabetes, I am working through a little (ok a lot of) anger, so have been bouncing around with ketogenics. Denial. Please finish that book up (TRIM) so I can settle in and be happy about doing something lifesaving for myself. By the way, you are looking radiant!! Very pretty!!

  5. Hi Mary!

    Thanks for the lovely comment! It’s nice to hear. If you liked Food Rules, please don’t forget to let folks know on Amazon. Every little bit helps!

    Dr Cate

  6. Hi Dr. Cate,

    Thank you so much for your reply. I can’t wait for your new book. I keep reading and re-reading your previous two books. They are excellent. I learn something new each time I go back to them. I have a social circle of about 10 ladies and we have all purchased your books. We are all eating meat on the bone and making bone broths. As a matter of fact, right now I have chicken broth cooking on my stove…with the feet! 🙂

    Thanks again for all you do. You’re a life saver!


    PS – And yes – you are so right when you say that this is the way our grandmothers ate. My Mom, who is 86, ate – and eats – just as you advise. It’s how I ate growing up but fell away from it in the low-fat crazy. In any event, my Mom is in amazing health, with gorgeous skin, strong bones, and all her own teeth!

  7. Hi Mary!
    Cutting carbs is hard to do for good reason: Your body is not tuned to burn fat yet. Which is why, in TRIM, we switch out old habits for new, old meals for new, gradually. And yes thank you so much for asking! Our next book will explain all about how to adapt a low carb/super healthy diet without feeling awful or missing those carbs. Believe it or not you won’t even miss ’em! We hope to have the book done in the next 6 months. Stay tuned and stay well!

  8. Hi Dr. Cate,

    This was so interesting. I would like to eat 50 grams of carbs per day but I find it hard to achieve it. Is it just getting over those initial few days of not feeling great? Also, will you have any advice as to how to do this in your upcoming book? And speaking of your new book…when will it be out…I can’t wait to read it!!!



  9. Paracelsus: My efforts lasted 3 months. I certainly understanding that an adjustment period is needed.
    I suspect more is going on here. Folks are different and there is not one diet that works for everyone. I know folks who thrive on the Paleo diet and lose weight and perform well. I also know folks who eat a high starch diet and also lose weight and perform well. Not sure I can explain it, but I am coming to the belief that someday we all will be able to determine the correct diet for each individual.

  10. This is a topic I’ve wondered a lot about and still I’ve never been able to get a complete understanding of.

    I’ve been a soccer player all my life and hope to play semi-professionally at some point. In general, I eat for optimal health, which at this point is basically a mish-mash of the recommendations from Deep Nutrition, Mark Scisson, Dr. Kurt Harris and a few other similar sources.

    I’m still unclear about carb intake/carb loading for athletics that require a lot of anaerobic activity (like soccer). Up to this point, I can’t pin down a difference in performance based on what I’ve eaten recently, although I do find myself craving raw milk after a long game (probably because that’s usually my biggest source of sugar/carbs).

    I don’t know if you’ve heard of the couple that runs the Perfect Health Diet blog, but their recommendations involve eating more starches and such than their paleo-esque counterparts. I think they generally recommend stuff like white rice, potatoes and yams. Here’s one of their posts on carb intake, which I think has a bunch of links to other posts about their opinions on ketosis and so on:

    I’m curious as to what you think about carb intake and anaerobic sports. Get some fruit before a game? Starches? Traditionally prepared grains? Or is fat the be-all-end-all?

    Thanks! Your blog/book are awesome by the way.

    1. Josh
      The literature on athletic nutrition is clouded by wrong assumptions (natural fat is bad for us) and plain old being out-of-date (the idea that nutritional ketosis is an unhealthy state), which means any answer I give you is oing to be based primarily on conjecture.
      The principal to remember is: Your body gets good at doing what it does most often. If you frequently ask it to dig down deep into your glycogen stores, and you can store between 1K and 2K calories in the muscle and liver in the form of glycogen, you will be able to use up the last bits of glycogen, which are “harder” to get at more readily.
      For more info, Dr. Stephen Phinney at UC Davis has done the most work on sports performance in nutritional ketosis.

  11. Hi Dr. Cate,
    Can you comment on the accuracy of reagent strips in assessing keto-adaptation. I bought some out of curiosity. I have been getting “trace” or “small” readings during times when I should be ketonic. Is it possible that if ketones are being used efficiently they won’t show in the urine? I assume I’m in ketosis when my wife say’s that I stink like garlic. I’m generally pretty low carb. I feel great and have plenty of energy. I had significant weight loss in the first 3 months, and have maintained my current 22 BMI pretty effortlessly for a year. Interestingly, I’m not thirsty very often and I’m quite active. I often take meals w/out a beverage. I hope this sounds like a ketogenic metabolism.

    Thanks! Mike

    1. Mike
      Most reagent strips are designed to detect diabetic keto-acidosis and are not sensitive enough to reliably detect nutritional ketosis, so trace or small is probably right where you want to be.

  12. Bobby, I suspect you’re missing something very important. It’s why so many studies have concluded that ketogenesis hinders athletic performance. Did you actually take 3 solid weeks eating a ketogenic diet before assessing your performance? If your body’s still asking for sugar and you give it fat, like a little kid it’ll throw a tantrum and keep asking for sugar in spite of you. It takes time for it to accept that you’re not eating alot of carbs, so it’s got to do a good job of using fat. You need at least a good 2-3 weeks of ketosis before you can assess how you perform on high fat vs. high carb.

  13. Bobby, very interesting. You may have a metabolic issue with converting protein to glycogen, which is why it’s good that you are listening to your body. And best of luck in your continued sports succes!

  14. Based only on my personal experience, I respectfully disagree with your conclusion. I have experimented with low carb, high to moderate fat, and high protein diets ( Paleo) on at least three different occasions and I have found myself getting weaker as time went on. When I quit the diet and increase my carbs my running performance improves.
    I have run 24 marathons and fortunately have never hit the wall.
    I really believed and wanted the Paleo diet to work and love the foods I could eat, but the proof was in my performance. It failed me.

  15. OMG this just cracks me up. After watching the movie called “The pursuit of happyness” with Will Smith and in one scene he has to run all out for a bus, I realized that I couldn’t run like that if I had to and started working on a sprint routine. Now I can run for my life if I had to, but probably not across the country like in “War of the Worlds”.

    I’ve been Primal since last October and just had lab work done and all my biomarkers have improved by quite a lot – in fact all are now in the normal range. I’m thrilled and now I would just like to get off the last 20-25 lbs or so.

  16. Hey Dr. Cate,

    I have a question about Carbs and muscle-building. I know that you’ve already said something to the effect that you don’t need carbs to maintain or keep muscle, but what about someone who does heavy weightlifting? I’ve heard that carbs are important for people who need to have a steady stream of ATP for high-power movements (think Olympic-style Weightlifting, or Sprinting), mostly because the body converts glucose into ATP for short, intense exercises. Is it possible while in Ketogenesis, the body can create ALL of the glucose that it needs from fat and proteins? Is this a feasible assumption? I know that for a regular sedentary person, carbs aren’t necessary at all, but what about for a highly functioning strength/power athlete?


    Steve Scarfia

    1. Steve
      You’re correct, no need for carbs to replenish ATP. Protein can be converted to carb/muscle glycogen and when keto-adapted you don’t need that much carb in storage only, as you say, for the anaerobic stages of exercise which are short due to the acid buildup. Besides there’s carb in so many yummy foods: Milk, tomatoes, nuts, peas, etc., that unless you’re on an all meat lettuce only diet, you’ll get 30-50 gm per day anyway.

  17. Yep, and those on a ketogenic diet can also run at 299,792,458 miles per second, enabling them to stay ahead of the alien’s extreme speed, while those on a high carb diet simply can’t. Ketogenic diets = win. High carb diets = crispy 🙂

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