Rewriting The Fat Burning Textbook – Part 1: Why You’ve Been Lied To About Carbs And How To Turn Yourself Into A Fat Burning Machine.

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Articles, Low Carb & Ketogenic Diet

Lying facedown on a cold, vinyl-plastered laboratory bench, I grimaced and squirmed uncomfortably as a medical technician yanked a giant biopsy needle out of my right quad – sucking nearly 200 milligrams of my precious muscle fibers out of my leg. 

I knew my left quad and both butt cheeks were next in line to get more of my living tissue brutally extracted, so I braced myself and prepared for the next sharp needle jab.

It's not like uncomfortable self-experimentation is something new to me, but this scientific venture of muscle and fat biopsy was an even deeper dive into the pain cave than I'd experienced in the past…

…including the extensive bloodwork and biomarker testing I did to discover the damage that back-to-back triathlons on the most difficult course in the US do to the human body…

…the strict high-fat ketogenic state I followed for 12 consecutive weeks to see if it's possible to race an Ironman triathlon in under 10 hours without eating carbohydrates (which made wandering past any halfway decent Italian restaurant incredibly difficult)…

…and my combination of cold thermogenesis, electrical stimulation, extreme isometrics, hypoxic training, and Chinese adaptogens to train at just 25% of the normal Ironman triathlon training volume.

For this latest experiment involving giant biopsy needles, I had ventured into one of America’s top human performance laboratories to hammer on a treadmill for 3 consecutive hours while measuring fat and carb oxidation, blood lactic acid, oxygen utilization, fat and muscle composition, blood glucose, insulin (and much more) to see how successful my efforts have been to hack my metabolic efficiency and train my body to become the ultimate fat burning machine.

And now, you’re about to read the story of how I discovered the human body’s true fat burning potential, how you can turn yourself into a fat burning machine, and why you’ve been lied to about carbs.


Why You’ve Been Lied To About Carbs

Open any textbook on human performance, read any magazine article on workout nutrition or review any research produced by the world’s leading exercise and diet science institutes, and you’ll see the same two pieces of standard advice churned out with robotic-like repetition:

Standard Piece of Advice #1. Before any big workout days, eat seven to ten grams of carbohydrate per kilogram of body weight daily for optimal performance. On any other days, eat five to seven grams of carbohydrate per kilogram of body weight.

So how many carbs is that? Let’s do the math. 7-10 g/kg of carbohydrates is about 3-4.5 g/lb. So in the 24 hours before a heavy workout day, a 150 pound male would be advised to eat roughly 450-675g of carbs. And that’s 1800-2700 calories of carbs per day – the equivalent of 38-56 slices of bread. Or 17-25 bowls of cereal. Pick your poison.

And on any average day, even a non-workout day, you’d be advised to eat around 2-3 g/lb, or 300-450g of carbs. That’s 1200-1800 calories of carbs per day. So if you were eating a relatively typical 2500 calorie per day intake, you’d be looking at about 50-75% carbohydrate based diet.

Don’t believe me? Does 50-75% seem like too much to you? Sadly, this level of carbohydrate intake is status quo for the gold standard in athletes and exercise enthusiasts.

As a matter of fact, I frequently travel as a speaker, coach and athlete, and actually began writing this article from my bedroom at the IMG Sports Academy in Florida, where children and teenagers (along with recreational, collegiate and professional athletes) come to study and train. The facilities here are amazing and immaculate, and I’m physically sitting located about 100 yards away from the Gatorade Sports Science Institute (GSSI) (where I was exercising just this morning).

The GSSI is widely considered one of the world’s top go-to resources for cutting-edge exercise and nutrition science advice – which is probably why Gatorade vending machines dot the campus here, and the majority of the kids seem to be walking around campus with a never-ending big gulp-sized cup full of sports drink.

Anyways, here’s an excerpt on recommended carb intake from GSSI’s Sport Science Exchange Journal. Note that they actually go as high as TWELVE grams in this particular article:

“Adequate dietary carbohydrate is critical to raise muscle glycogen to high levels in preparation for the next day’s endurance competition or hard training session. Accordingly, during the 24 h prior to a hard training session or endurance competition, athletes should consume 7-12 g of carbohydrate per kilogram of body weight. However, during the 24 h prior to a moderate or easy day of training, athletes need to consume only 5-7 g of carbohydrate per kilogram of body weight.”

Here’s another excerpt from a different GSSI article:

“Soccer players’ diets, especially in the days before hard training or competition, should include 8-10 grams of carbohydrate per kilogram of body weight (3.5-4.5 g/lb). Cereals, fruits, vegetables, breads, and pastas are good sources of carbohydrates.”

Incidentally, a serving of Gatorade has about 25-35g of carbohydrates. Just sayin’.

OK, let’s move on to Standard Piece of Advice #2…

sugar in gatorade

Standard Piece of Advice #2. Ensure that during exercise, you keep your blood glucose levels evaluated by consuming the majority of those carbohydrates are from fast-burning carb sources such as sugary drinks, gels, and bars during both prolonged activity (like a long run) and also intense activity (like weight training).

For example, from this GSSI article:

“The advice for prolonged endurance events (2.5 h or longer) is an intake of 90 g of multiple transportable carbohydrates per hour. This advice is not expressed relative to body mass because body size/mass appears to play no major role in exogenous carbohydrate oxidation.”

So what the heck does “multiple transportable carbohydrates” mean? In most cases, this refers to the standard two primary ingredients you’ll see featured in just about every sport drink and energy gel on the face of the planet: a mix of fructose and maltodextrin sugars.

From another GSSI article:

“Given that there is no known detriment to consumption of a high-carbohydrate diet (other than body weight gain due to water retention) and some research reports a benefit, it is recommended that all athletes consume a high-carbohydrate training diet, i.e., at least 60-70% of energy as carbohydrate (7-10 g/kg), and increase this to 65-85% for the few days before competition. Use of a carbohydrate supplement before and during exercise will likely improve performance of intermittent, high-intensity sprints.”

The “no known detriment to consumption of a high-carbohydrate diet” part of that statement above is very damn disturbing. You’ll learn why in just a moment.

However, at the risk of appearing to be on a completely biased anti-Gatorade rant, and to drive home the point that a relatively enormous intake of carbohydrates is recommended for performance, I’ll also point out this anecdote from the “Nutrition And Athletic Performance” position statement from the American College of Sports Medicine:

“For events longer than 60 minutes, consuming 0.7 g carbohydrates·kg-1 body weight·h-1 (approximately 30-60 g·h-1) has been shown unequivocally to extend endurance performance. Consuming carbohydrates during exercise is even more important in situations when athletes have not carbohydrate-loaded, not consumed pre-exercise meals, or restricted energy intake for weight loss. Carbohydrate intake should begin shortly after the onset of activity; [and continue] at 15- to 20-min intervals throughout the activity.”

And from the International Olympic Committee's “Consensus Statement on Sports Nutrition” for longer exercise efforts:

“To achieve the relatively high rates of intake (up to 90 grams/hour) needed to optimize results in events lasting longer than three hours, athletes should practice consuming carbohydrates during training to develop an individual strategy, and should make use of sport foods and drinks containing carbohydrate combinations that will maximize absorption from the gut and minimize gastrointestinal disturbances.”

Are you getting the feeling that the Holy Grail of nutrition for athletes seems to be to protect carbohydrate stores at all times?

You’d be right with that feeling.

The general argument for carbohydrate consumption goes something like this:

Physical or mental fatigue during workouts (or while you’re sitting at your office) is caused by the low blood glucose that occurs as your carbohydrate fuel tank approaches empty (also known as the infamous “bonk”, which is awesomely demonstrated in this funniest running cartoon I’ve ever seen). Because it is generally (and sadly) accepted as orthodox knowledge that the human body can’t burn fat as a reliable fuel source – especially when you’re exercising for long periods of time or at high intensities – nearly every shred of nutrition science is simply looking for ways to somehow increase the size of your carbohydrate fuel tank and hack the body to allow it to store more carbs or absorb carbs more quickly.

Ironically, these efforts to encourage sky-high levels of carbohydrate intake are continued despite the fact that even the leanest of people naturally have tens of thousands of calories of readily accessible storage fat.

In fact, most folks have enough stored body fat to fuel low level activity for days and days without running out of energy. For example, a 150 pound dude at a hot, sexy and ripped at 8% body fat still carries 12 pounds of storage fat – which at 3500 calories per pound of fat can easily liberate 42,000 calories of useable fuel for exercise. You’ve got those same thousands of calories sitting around your waist, abs, hip, butt and thighs – just sitting there, waiting to be burnt.

Yet, it’s still standard advice to eat Wheaties for breakfast, guzzle Gatorade during a hard workout and to down a sugary Jamba Juice as you walk out of the gym. And this is the message being preached worldwide to kids and adults by exercise nutritionists and scientific bastions of diet research. We accept this as status quo.

Just think about it: when was the last time you ate a Powerbar before a workout? Had a big smoothie before you hit the gym? Finished up a workout and dumped some kind of powder into your blender (check the label and you’ll probably see maltodextrin and/or fructose as primary ingredients)?

Now, there is absolutely no arguing with the fact that high carbohydrate intake before, during and after a workout can certainly improve performance. So sure – there is at least some logic to the standard recommendation that you should consume a diet which provides high carbohydrate availability before and during exercise.

But while carbohydrates can help you have a better workout, go faster, or go longer, this only applies to acute, in-the-moment performance. Once you take a look (which you’re about to do) at the long-term effects of chronic high blood sugar levels, things change drastically. If the damage that you’re above to discover is worth it to you, then you are either mildly masochistic or you value performance much more than health. Perhaps you fall into the category of Olympic athletes who would dope with damaging drugs, even if they knew it would kill them. However, if you desire a long, high-quality life, you don’t want to be a washed up ex-exerciser with diabetes, or you don’t want to experience joint, nerve and brain inflammation, damage and degradation, you may need to adjust your lens.

Your lens?

That’s right.

This all depends on the lens through which you view your body and value your health, and your own personal philosophy on performance vs. health.

So what is your lens? Are you chasing performance and a better body at all costs, or are you willing to entertain the idea of thinking outside the box and defying standard practice if it means that you can achieve the same or superior levels of performance, and a better body, but with superior long-term health implications?

Before we discover the answer to that question, let’s delve in and find out what happens if you actually listen to the standard advice to fuel your workouts with massive amounts of “healthy” carbohydrates.


What Are The Dangers Of Eating Carbs?


After living on a high-carb, junk-food diet and then switching to the high-protein, low-fat, low-carb diet, I’ve toyed and tinkered with a Paleo diet, a raw vegan diet, an Atkins diet, and a ketogenic diet.

And the #1 prevailing characteristic that defines how good or bad I feel on any of these diets is the amount of sugar and refined carbohydrates, regardless of any of parameters (e.g. milk vs. no milk, legumes vs. no legumes, etc.)

Turns out it’s not just me.

Every month, I review dozens of clients’ blood lab testing results, and the same pattern pops up over and over again: The higher the sugar and starch intake, the higher the blood triglycerides, the greater the inflammation, the worse the sleep, the more difficulty controlling body fat levels, and so on. Once relatively nutrient-void, fast-release carbohydrate sources such as energy bars, whole-wheat bread, granola, cereal, muesli, pasta, etc. are replaced with more nutrient-dense and healthy fats, moderate amount of proteins, and plenty of vegetables, blood biomarkers and performance quickly begin to take a turn for the good.

The bullet points below will help you understand the risks of consuming carbohydrate levels like “7-10g/kg” (if you want more details and studies behind some of these points, read this excellent article from the Life Extension Foundation).

-Cancer: Numerous studies have found that the risk for cancer increases with high blood sugar, which makes sense, since cancer cells feed primarily on glucose. This includes cancers of the endometrium, pancreas, and colon and colorectal tumors. Tim Ferriss recently hosted a fantastic article by Peter Attia about this very issue, and how ketosis may indeed be a potential cancer cure.

-Cardiovascular Disease: High blood sugar has been shown to increase the risk for cardiovascular events, cardiovascular disease, and cardiovascular mortality—while lower glucose levels result in lower cardio- vascular risk. Coronary artery disease risk has been shown to be twice as high in patients with impaired glucose tolerance, compared with patients with more normal glucose tolerance. The risk for stroke increases as fasting glucose levels rise above 83 mg/dL. In fact, every 18 mg/dL increase beyond 83 results in a 27 percent greater risk of dying from stroke. Incidentally, glucose can “stick” to cholesterol particles and render these particles extremely dangerous from a heart health standpoint, which is why it’s all the more important to control blood sugar levels if you’re eating a “high-fat diet.”

-Cognitive Issues: High blood sugar results in cognitive impairment and dementia.

-Kidney Disease: Surges in blood sugar drive the production of fibrous kidney tissue and vascular complications in the kidneys, which can cause chronic kidney disease. There is a direct increase in chronic kidney disease as levels of hemoglobin A1c (a three-month “snapshot” of glucose control) rise.

-Pancreatic Dysfunction: The beta cells in the pancreas that produce the insulin to help control blood sugar become dysfunctional with high blood glucose, raising the risk for type 2 diabetes. Researchers have discovered that beta cell issues are detectable in people whose glucose levels spike two hours after eating, despite those levels staying within the range considered normal and safe by the medical establishment.

-Diabetic Retinopathy: Diabetic retinopathy is damage to the retina that can lead to blindness—and it is highly aggravated by high blood sugar.

-Nervous System Damage: It’s been shown that patients with neuropathy whose after-meal glucose readings were above the diabetic threshold sustained damage to their large nerve fibers. Even neuropathy patients whose glucose readings remained well within the normal range showed damage to their small nerve fibers. Studies have shown that within any blood sugar range, the higher the glucose, the greater the damage to nerve fibers.

I don’t know about you, but I find these risks pretty damn concerning. The fact is that I want to be around to play with my grandkids, and considering that my genetic testing with 23andme has revealed that I have a higher-than-normal risk for type 2 diabetes, I doubt that shoving more gooey gels and sugary sports drinks into my pie hole is going to do my health any favors. So if I can achieve similar levels of performance and body composition with carbohydrate restriction, I’m all in.


Zach Greenfield

Fat Loss Benefits From Eating Fewer Carbs

But let’s say you have a hard time thinking 20 years ahead to your future health prospects.

Perhaps diabetes and joint degradation seem like a long way off to you, and it’s tough to get motivated by those vague concepts. You just want to rock your workouts, feel like a million bucks and look good naked – right now. In that case, there still a multitude of benefits to controlling blood sugar and lowering carbohydrate intake.

For example, a key component of safe and lasting fat loss is your capability to tap into your body’s own storage fat for energy. This access to fat cannot happen if your body is constantly drawing on carbohydrate reserves and blood glucose for energy. In the type of moderate- to high-carbohydrate diets you’ve learned are widely recommended by prevailing nutrition science, not only does the utilization of fat for energy become far less crucial (since you’re constantly dumping readily available sugar sources into your body), but your metabolism never becomes efficient at using fat. There is a growing body of evidence proving that a high-fat, low-carbohydrate diet results in faster and more permanent weight loss than a low-fat diet. Furthermore, appetite satiety and dietary satisfaction significantly improve with a high-fat, low-carbohydrate diet that includes moderate protein.

A study in the Journal of Applied Physiology showed that people who do twice-a-day workouts, but defy standard nutrition recommendations by not eating for two hours after the first session (thus depleting carbohydrate stores with the first session) experienced a better ability to burn fat (with no loss in performance) compared with a group that trained only once a day and ate carbohydrates afterward.

Another study deprived participants of carbohydrates then subjected them to high-intensity interval training on a bicycle – and showed better fat burning and an increase in the enzymes responsible for fat metabolism, again with no loss of performance.

And biochemistry research shows that when carbohydrate stores are depleted by almost 50 percent (e.g. by doing a workout without eating carbohydrates), there is increased stimulus for enhanced enzyme activity in skeletal muscle – which is a good thing, since it means that you can more efficiently produce ATP energy from fat calories.

If you want even more good news about carbohydrate restriction and enhanced fat burning, then read “The Art & Science of Low Carb Living”, which delves into even more thoroughly into low-carb fat-burning research and practical tips. That book happens to be co-authored by Dr. Jeff Volek – the same researcher who put me through the brutal treadmill protocol you’ll read about in just a bit.

And should you just want to look good naked, you can check out this article featuring my brother Zach Greenfield (pictured above) or you can click on any of these photos of my ketogenic, high-fat, low-carb bodybuilding friend Chaz Branham, 13 weeks into his high-fat, low-carb diet.







Performance Benefits From Eating Fewer Carbs

But the benefits of going low carb don’t stop at fat loss.

For example, in trained people and athletes who eat a low-carbohydrate, high-fat diet (not to be confused with a low-carbohydrate, high-protein diet), a large amount of fat burning can take place at intensities well above 80 percent maximum oxygen utilization (VO2 max) – allowing for very-high-intensity or long efforts with low calorie intake and also allowing for use of fat fuel stores during long steady-state exercise, even at a relatively fast pace (so much for the “fat burning zone” giving you the best bang for your buck). With high-fat, low-carb intake, you can go hard and still burn tons of fat. In addition, this means that more carbohydrate stores will be available when you really need them, such as for an all-out, 100%, maximum effort.

You also get incredible gains in metabolic efficiency when you use fat as a primary source of fuel – especially when doing high-intensity interval training – with this one-two combo causing potent 3–5 percent decreases in the oxygen cost of exercise, which is extremely significant. Translated into real- world numbers, this increased fat utilization from carbohydrate restriction and high-intensity interval training would allow you to pedal a bicycle at a threshold of 315 watts, whereas a high-carbohydrate, aerobic-only program (the way most people train) would allow for only 300 watts. Talk to any cyclist and you’ll find out that an 15 extra watts of power is huge in a sport like cycling, and something most cyclists train years and years to achieve…

A high-fat diet also trains your body to burn even more fat during exercise, even at high intensities. Fat is released faster and in greater amounts from your storage adipose tissue and transported more quickly into your muscles and mitochondria. Your muscles also store more energy as fat and use this fat-based fuel more efficiently and quickly. Even more interestingly, a high-fat diet can cause a shift in the gene expression that codes for specific proteins that increase fat metabolism – and create very similar adaptations to exercise itself. So the mere act of shifting primary fuel intake from carbohydrates to fat begins to make you more “fit”, even if you’re not exercising.

And guess what else?

This benefit surprised me when I first discovered it, but eating fewer carbohydrates during a workout can actually help you recover from workouts faster. The repair and recovery of skeletal muscle tissue is dependent on the “transcription” of certain components of your RNA. And a bout of endurance exercise combined with low muscle-carbohydrate stores can result in greater activation of this transcription. In other words, by training in a low-carbohydrate state, you train your body to recover faster.

But sadly, whether due to government subsidy of high carb foods like corn and grain, funding from big companies like Gatorade and Powerbar, our sugar-addicted Western palates, or the constant (unfounded) fear mongering about saturated fats and heart disease, the type of research that shows these fat-burning and performance benefits of carbohydrate restriction simply get shoved under the rug.

In addition, most studies that compare carbohydrate utilization with fat utilization fail to take into account the fact that full “fat adaptation” that allows you to gain all the benefits of using fat as a fuel actually takes time – often more than four weeks – and up to a couple years. But since most studies that compare fat and carbohydrate burning are short-term, you rarely see the benefits of this kind of fat adaptation actually fleshed out in research. Instead, the average research participant begins the study in a non-fat adapted state, gets either a high fat or high carb diet, then launches into exercise. But in an ideal study, that person would have followed either a high-fat or high-carb diet for many months before getting their fat burning capability investigated.

So the textbooks and the nutrition science recommendations stick to the standard two pieces of advice you learned about earlier, and continue to preach that to be a good exerciser, to get maximum performance and to optimize your workouts, you need to be a complete carboholic.

But what if this wasn’t true?

What if we could prove that eating a low-carb, high-fat diet for a long time, becoming fat-adapted and even avoiding carbohydrates during the one time when we’re most encouraged to consume carbohydrates (during exercise)…

…could actually turn you into a fat-burning machine without losing a shred of performance capability or causing any metabolic damage?

That, my friends, would rewrite the fat-burning textbooks.

Let’s find out if it can be done…

Tune in tomorrow to delve into Part 2, which will feature the nitty-gritty lab testing steps, the mildly disturbing photos, and the shocking results that are now rewriting the fat burning textbooks. You can click here to subscribe to my free newsletter to get an instant e-mail notification when that article is released…

…in the meantime, leave your questions, comments and feedback below and I promise to reply.

Ask Ben a Podcast Question

65 thoughts on “Rewriting The Fat Burning Textbook – Part 1: Why You’ve Been Lied To About Carbs And How To Turn Yourself Into A Fat Burning Machine.

  1. Lindsey says:

    What are your recommendations if you are overweight and not able to exercise at high amounts?

    1. Start here and let me know if you have any questions:…

    2. Debbie says:

      Carnivore diet

  2. I suppose this will be covered in part two, which I’m yet to read (so behind on uni study……), but I read an article by Peter Attia, which explained how he was able to take in heaps of carbs (I mean like 200 or something, heaps relative to ketogenic amounts) and stay ketotic. It was due to a thing called glycogen deficit. I couldn’t really follow it, it didnt make much sense. Maybe it’s me being the stupid footy-loving, kebab-munching bogan I am, but I really didn’t get it.

    Could you have a go at explaining this to me (if you know what I’m on about……..)?
    Here’s Peter’s article

  3. Andy says:

    Hi Ben,
    I went on a keto diet to do do an ironman, following your training plan, with great success.

    I have tried to convince my wife do do the same but she had kidney stones when she was younger and has been told never to go on a high fat diet, because of that.

    Is this true and have you any advice for her ?


  4. paul says:

    Ive been on a ketogenic diet for a year and half. I was very strict untill the hollidays, which i saw a big difference in muscle fatigue. Normally i would never notice muscles getting tired while i was eating under 20 grams of carbs a day. As soon as i started cheating a bit it was like it was when i first started, altho it didnt take my body much to get back to using the fat for fuel. In the past 1 1/2 years ive put on 15-20 pounds of muscle while dropping my body fat from 10-12% to 6-8% with almost no training or wieghts. My muscles seem to get sore from day to day things that they never did before which i attribute to the muscle gains

  5. runbei says:

    Ian Jackson, my roommate in the early 1970s, once ran 140 miles in a week – while fasting on only water. He felt fine throughout – ran it all as daily 20-milers on very hilly trails, mostly at 6:30 to 6:00 pace. Ian was in a state of ecstasy on the last run.

    Compare: When I went on a very low fat diet, my weekly 3.5-hour hilly runs became absolute death marches. The brain and heart are the body’s most carb-hungry organs; thus the body never actually runs out of carbs but spares some to preserve life. When i began eating just 1 cup of rice per day, I immediately felt fine.

    Consider: The Kenyan elites eat up to 70% of their caloric intake as carbs.

    Consider: Arthur Lydiard’s runners, who absolutely blew the interval-trained runners of the 1950s away, consumed huge amounts of carbs right after their three long runs per week (10, 15, and 22 miles).

    Consider: Hammer Nutrition advises eating enough carbs to replenish calories lost immediately after each run, because these are the carbs that will fuel the next run. On other days, eat carbs very moderately.

    My point is that the variation in the ability to utilize bodily fats for energy is huge – thus Ian Jackson’s amazing feats while fasting. And therefore, as Ben states, adaptation to using more fats can take 4 weeks to a year.

    Frankly, when people advise diets that require MCT’s, tons of coconut oil, etc., I’m very suspicious. From my own experience, I know that much less carb is needed than the standard advise would imply. But my body has a tough time converting to burning mostly fat, and I’m not sure I want to endure a month to a year of absolutely horrible exercise experiences to make the shift. Surely not merely to lose weight, which I’ve managed to do quite nicely on a high-nutrient-quality diet (tons of salad and beans, a few eggs, some fish, etc.), and “just enough” carb to fuel exercise and daily life.

    I feel fine on this regime, recover quickly (at age 72), and am able to lose weight and keep it off. Not sure I understand the need to become a fat-burning machine.

    I formerly did ultras of up to 100K – slowly, I’m not a talented runner and have partial paralysis and spasticity in my legs. I would often do long training run/hikes of 6-7 hours on NO fuel. If the terrain was mountainous, I would take along just one energy bar and nibble on it once an hour.

    Those runs were fine but the recovery was horrific. It’s known that unfueled runs make the body produce high levels of cortisol; thus people who do these runs tend to look prematurely aged. Conclusion: my body sucks at fat conversion, and I’m not sure a fat-only diet doesn’t pose hidden dangers (cortisol, premature aging).

    The idea of burning fats is attractive; but I haven’t found a way to do it that seems enjoyable, or without possible dangers.

  6. richgeres says:

    To me it looks like we're mixing up two different topics here: Nutrition for performance, and nutrition or fat-loss.

    From the standpoint of athletic performance, especially for endurance sports, there is no doubt that a high carbohydrate diet provides a competitive advantage. Trials conducted on athletes on a high fat diet, which was changed to a high carbohydrate diet days beore the race showed that thier performance increased once on a high-carbohydrate diet.

    I don't know of any fat professional endurance athletes. I don't have any figures of endurance athletes who are diabetic as a result of carbohydrate overconsuption, but I doubt the numbers are high.

    For fat-loss, a low carbohydrate diet definitely works,and if you want to take it to an extreme, a ketogenic diet works well too, although it is uncomfortable to follow. I've tried it myself and managed to reach 5% bodyfat with it. However, there is no way your performance is anywhere close to where it would be on a high-carb diet.

    Therefore proposing a high fat diet for superior athletic performance doesn't make sense to me.

    1. The two topics I am mixing are ‘superior health and longevity’ with ‘no decline in performance’. Did you read Part 2?…

  7. Steve C says:

    Ben, Great article! I’ve been looking into changing the way I fuel for training, had a go at coconut oil, but just can’t get it down. I come across fractionated barley (virtago) is its branded name, any thought on using this?

    From researching it, it too has a low release of insulin like coconut and MCT oils.

    Keep up the good work.


    1. Vitargo actually causes quite a large spike in blood sugar! Take a look at the question from Bill on…

  8. Flo says:

    Great article with so many good points. Rad To see how much you experienced with this. I cut out all processed carbs and refined sugars about 12 months ago And have noticed a huge difference in Energy levels during the day plus lots of improvements on my longer runs.

    I havent experienced any bonking at the 20-25 mile mark. The night before my first 50 mile race in January I didnt eat any carbs, I wasnt sure what to expect but again the body worked fine, 7 hours 25 with HR between 140-165 and no bonking.

    Thanks for sharing this detailed article!

  9. MattPhD says:

    I guess the ACSM (American College of Sports Medicine and the ADA (American Dietetic Association) are both wrong! This is just another guy trying to make headlines on the internet….…

  10. chungpao says:

    Most significant benefit of carb-free diets, in my experience:

    cAMP: Cyclic adenosine monophosphate.
    Carbs are directly antagonistic to cAMP.

    cAMP mediates the effect of all catecholamines (dopamine, norepinephrine, adrenaline) and many other molecules.
    It's a determinant of how fast you adapt to anything, doing so by stimulating the gene expression.
    See PKA and Adenylyl cyclase/G-stimulatory proteins for more info.

    To really understand the effect of cAMP, you can use a very low dose of forskolin (1-5 mg) preworkout.

    However, carbs are directly antagonistic to cAMP.
    Which is why I minimize their intake to carb-sources which contain unique nutrient-compositions I feel are essential to my performance (veggies, lentils).

    If you have any related thoughts, or want to correct me, please do so. I'm just here to learn.

  11. hurls says:

    I would LOVE some feedback on this. Me (6'2" 185# athlete) and my wife got very much into strict Paleo (including no dairy or fruit) in 2011 and this article would have been something I would have loved back then. But, after a few months of feeling great, we quickly crashed. I was down to 155 pounds and was lethargic, weak, and rarely went to the bathroom. We finally decided to abandon it and found Matt Stone's recovery plan (high calorie, high carb). We've been slowly getting better over the past 3 years, but our metabolisms are still damaged. I feel much better, but am stuck at 200# with bloating and stomach issues. My wife's hormones are a wreck. We discovered the hard way that very low carb is a huge mistake and have read over and over again that the long term effects of it are just as bad. It's consumed our lives and is very frustrating. Her body is so messed up, we can't have any more kids. I spend 60+ minutes in the bathroom each day and have a tire around my waist. Any ideas!?! :-(

    1. You absolutely must keep up the nutrient density of your meals. Listen to this interview with Dr. Wahls – she knows how to do low carb / ketogenic the right way.…

  12. Pete says:

    Hi Ben

    So in short, with training and eating fat as your main fuel source, its possible to increase your anaerobic threshold and continue burning fat at high intensity?

    Do you have any studies/refs to back this up?


  13. paleophilo says:

    Excellent article. I reposted it. Waiting for tomorrow !!!

  14. Jeff Lloyd says:

    Great article Ben, and I’m looking forward to part 2! I very much understand Ketosis and how to get into it….But I thought in order to stay in ketosis carbs have to be 50g or less a day…Isnt it possible to not be in ketosis, but be fat adapted (beta oxidation)?

    1. This is something I've covered many times on podcasts, but basically, it's not true. You can eat up to 200g or more of carbs per day and still be in ketosis if you're physically active or ingesting large amounts of MCT oil or even liquid ketones.

  15. Justin says:

    I’m trying to read this on my galaxy phone but I can’t because all your advertisements are right in the middle of the screen covering up the text. I either need a mobile version of the sight or need to take that stuff of

    1. Wow. I will look into this ASAP.

  16. x10 says:

    Hey Ben, what do you think of 80-10-10 where the majority of the carb intake comes from fruits? Example 30 bananas a day?

  17. cookecc says:

    I agree with some of the above comments- I think this can work for some, but not all of us. I did a high-fat, low'er' carb diet for 8 months with horrendous results. Could barely walk up a flight of stairs towards the end. I started adding back in as much carbs as possible and feel a whole lot better. I know that goes against the grain, but some of us are just different- for whatever reasons.

    1. hurls says:

      I had EXACTLY the same scenario. I've never felt such lethargy and my body basically shut down on me. It was terrifying and I'm still trying to recover 2 years later.

      1. cookecc says:

        Ugh, sorry to hear that hurls. I am a year out, and still very damaged as you are. I am quite stunned actually that it is taking so so long to recover. It's amazing to me just how much damage it has actually done, and I'm not sure why the recovery is so elusive. Let's just hope it's reversible, it sure seems like I'll never return to the way I was before!

  18. DeadliftBrah says:

    I've always been a big proponent of High fat, moderate/high protein diets as a power lifter (with bodybuilding interest).

    I pretty much eat by IIFYM these days, so I was wondering if you could recommend a ballpark breakdown of carbs/fats/proteins as a % of your total caloric intake for a given day? (ie 20/40/40)

    1. Active days I am 60%F, 20-30%P, 20-30%C and low active days I am 80-90%F, 10-20%P, 5-10%C.

  19. Finn says:

    Define Low Carb.

    What do you eat?

    What about the resistant starch crew?

    Article is great but I need more details

    and plan. You need to address the

    “non-elite” athletes who follow your blog.

    1. Take a look at this… and… and for some real insight, recipes and an awesome forum Also, this is the book that I base my own nutrition off of… I hope that helps!

  20. m1class says:

    Ben, you really get me thinking with your great articles. I'm in my seventies and still enjoy road races up to ultra runs. I've been a vegan for over a year and am concern about oils and saturated fat causing coronary heart disease in older people. Years ago when runners used to carbo load for a marathon and in the depletion stage eating all protein and fats, I got so weak I could hardly walk and running was slower than walking. Is this low carb for older aathetes?

    1. Yes, it does work for older athletes, but I would ESPECIALLY READ THIS ARTICLE;…

  21. heliophilia0_ says:

    Hi thanks for great article. I’m 33, and haven’t eaten complex/starchy carbs since I was 18. The only carbs I eat are mainly in form of green veg, and dark chocolate (occasionally beetroot). I’m fit and lean, consistently train on average 5 times per week, never been injured, rarely get doms, rarely ill, rarely tired, and am often mistaken for being about 8-10 years younger than I am. I’m sure that this is largely thanks to my diet and convinced that you’re onto something. My feeling is that protein as key as fat, micronutrient balance key also, minimal carbs required for optimal performance and equally short/long term health. Good luck with your research, look forward to the follow up articles :)

  22. PaulB says:

    I have been a ketogenic state for a year now due to Epilepsy and have read “The Art & Science of Low Carb Living,” and followed it. Plus always did endurance activities before and after. My endurance, recovery…improved, but my ability to go aerobic /anaerobic/aerobic was obliterated. After peddling up for an hour in Zone 1-2, intense down hill mountain bike rides start where where my body goes into anaerobic states. Now, I get so tired, I need to rest for 3 min. But then I feel fresh as if it was the start of the day with no brain fog. Fat can get into the mitochondria quicker, but the breakdown of fatty acids/triglycerides is slower. So for weight lifting or sprinting its immediate energy until it needs to be broken down. For a 20 minute Supercross race where it is more anaerobic, I don’t think a high fat diet will work.

    1. That's where strategic use of carbs can come in handy. You don't have to abandon the diet as a lifestyle.

      1. paulb says:

        Exactly, This is what I need to do. Introduce carbs only when I know they will be immediately used by the needs of my body and not toss me out of ketosis. The Medical field is putting lots of people on a “Modified Adkins” diet for cancer to epilepsy, but I had to go < 40g carbs a day to get my life back.

  23. Geoff says:

    Does he not shoot himself in the foot withe the last paragraph….

  24. DMowmow says:

    I've heard there can be cold hands and feet, which I already have, with a kenogenic diet, as well as limp: you know.

  25. Anthony says:

    Always great to read an intelligent article on Ketogenic athletic performance. I have read many studies from Jeff Volek, Attia, D’Agostino etc. As a 50 year old recreational Ice Hockey Player and avid weight trainer, I have been unable to perform at a high level purely Ketogenic. Ice hockey (for the most part) is Anaerobic. The problem is that I cannot perform at a high level without some basic carbs or using a carb backload. Now if I were performing aerobically, I could reap all the benefits of a ketogenic lifestyle. I even tried Patrick Arnolds Keto Salts. It did help, but still not nearly the performance I am capable of. So, if anyone has the answer as to how I can create those quick burns of explosive energy for my sport, I am all ears!! Cheers!

    1. start with 1) patience and being in it for long term; 2) knowing that you can still be in ketosis at 150-200 daily g of carbs if your'e active; 3) lots of amino acids; 4) lots of HIIT training. I cover a ton of this in really big detail in

  26. Leonie says:

    Do you have any information about being fully keto adapted in the long term? I can see that low carb high fat will have long term benefits, but the next step ketosis seems a bit stressful on the body, which may be ok for a few years but how about in 30 years?

  27. Tony says:

    Started following LCHF two weeks ago and my energy is thru the roof! No problem with intervals, longer runs, or heavy lifting. All I need is water during the longer runs – and I’ve lost 7lbs.

  28. Natalia says:

    great article!!!!

    question it seems that the low carb-high fat diet works for better performance, what about muscle grow? it will be compromise for the low carb intake? thanks for the awesome info here :)

  29. Carol says:

    I can see this working for young, very active individuals but how about the (non hormonal supplementing) post menopausal woman? We seem to be a different breed when it comes to fat loss no matter how much weight we lift or aerobic exercise we do. Is there hope?

  30. srobison1977 says:

    Great article Ben! If I'm 6' 173lbs and keep my carbs below 200g per day on a ~3000 calorie diet, is that low enough? I've struggled to consistently stay below 150g per day.

    1. TIMING is more important than total intake – which is going to vary HUGELY based on your daily levels of physical activity. Best way is to test blood ketones or breath ketones to see if you're staying in ketosis if that's your goal, or to use a carb back loading strategy like John Kiefer's.

      1. Mike says:

        I an currently reading carb back loading, how similar are your strategies to kiefers? So far my experience is that my energy levels are incredibly consistent and workouts haven’t suffered.

        1. I love Kiefer's stuff. You can still do low carb, high fat with it. You're just stacking all your carbs until the end of the day. It's pretty much what I do. I just eat 100-200g of carbs instead of, say, 400-600.

  31. TavisRD says:

    Bob Seebohar has an incredible book on Metabolic Efficiency and training. At the same time, I have not see any data that demonstrates a low carb diet improves athletic performance. Phinney's study in 1983 had one outlier out of only 6 subjects and the rest did pretty poorly. That study has also not been replicated. Louise Burke's work out of Australia has also demonstrated a reduction in performance when following a low carb diet.

    Debate by Jeff Volek and Alan Aragon at NCSA –…

    For fat loss, this is the way to go or even practicing some Intermittent Fasting. For Sports performance, 20% carbohydrate will not improve exercise training and performance, it will actually impair it.

    1. Yes, you would be right – until tomorrow morning. ;)

    2. Sheila, RD, CSSD says:

      I have to agree with Tavis. I have seen many clients start on a High Fat Low Carb diet and feel good – but – not really seeing any improvement in performance and report feeling challenged to sustain this way of eating with family, kids, social gatherings. Many of my female clients cannot get away with eating fat ad lib. They gain weight despite the low carb intake. I would like to see a study that looked at women only. If you know of any please forward.

  32. Brian_Beaven says:

    Great article Ben. Lots of links to studies with supporting data. There is no doubt Americans especially athletes are consuming too many junk carbohydrates in the form of processed sugars. They should be getting their carbohydrates from whole food sources.

  33. Graeme_T says:

    We look back at things like chewing tobacco in absolute disbelief.

    I wonder if, in 100 years, people will look back at refined and manufactured sugars in the same way.

  34. SimMichJac says:

    I have been following a high fat, moderate protein, low carb diet for a year now and I love that I can train for long periods of time without getting tired or hungry. The majority of my fat comes from coconut oil, however I seem to have hit a weight plateau and no matter how many calories I eat, I can't seem to lose weight.

    1. Have you added in some heavy lifting and HIIT? That usually helps get people out of a weight loss slump. Take a look at this…

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