World-Class IRONMAN Triathlete Switches to a Low-Carb Diet – and Has His Worst Season Ever

Study after study after study has shown that when exercising individuals restrict their carbohydrates, their performance promptly declines.

In a world where many people have been fooled into believing carbs are evil, this is not a popular truth.

And so every time I point out the performance-destroying effects of low-carbohydrate ‘nutrition’, some angry low-carb zealot inevitably gets his XXXL panties in a twist and carries on like I’m the devil incarnate (for an especially vivid example of someone who did this, click here).

The scenario usually plays out as follows:

I write an article pointing out low-carb diets are an inferior choice for athletes. Incidentally, I receive no funding from anyone, including the sports drink/soft drink/sugar industries, for doing so. I write the article because yours truly, in a less-enlightened phase of his life many moons ago, once followed a low-carb diet and it hurt his performance on the bike.

Actually, “hurt” is an understatement: It would be closer to the truth to say low-carbing grabbed a hold of my cycling performance, pulled out a chainsaw, and went absolutely Friday the 13th on it.

It sucked, and I don’t want other people to suffer the same misery.

Low-carb zealots, however, refuse to acknowledge any benevolent intentions on my part. Instead, they promptly lose their caca and call me all manner of nasty names. They cite a list of studies they either haven’t read or don’t understand, like the infamous and poorly conducted cyclist study by low-carb shill Stephen Phinney.

I point out in detail why these studies don’t prove diddly, and reiterate that far higher quality studies show low-carb diets produce inferior performance when compared to higher carb diets.

Having lost the scientific argument, low-carb zealots then resort to the time-honoured tactic of anecdote.

What about Wally McBumpkin,” they triumphantly ask, “who won the inaugural 2003 Dingleville wheelbarrow racing championship while following the Atkins Diet? Huh? Take that, Colpo!!”

Yeah, I’ll take it … as a joke.

When I point out there were only two entrants in this grand inaugural event, and one was disqualified after passing out drunk prior to the start, my critics are not deterred. Oh no.

They promptly jump back aboard the Search Engine Express and feverishly search for evidence of somebody, anybody, who looks something, anything like an athlete and follows something, anything resembling a low-carbohydrate diet. They then present a list of people who, they claim, followed a low-carb diet and achieved athletic awesomeness (for an especially vivid example of someone who did this, click here).

But upon closer examination, it becomes apparent most of these athletes aren’t really following a low-carb diet. Furthermore, few if any of these allegedly low-carb athletes have competed at a truly world class level for an extended period of time while following their ‘low-carbohydrate’ diet.

borderA group photo of all the world-class, gold medal-winning athletes who we know for sure to follow a low-carb diet.

In 2018, however, the International Journal of Sport Nutrition and Exercise Metabolism published a case study of a bonafide world-class Ironman triathlete who followed a low-carb diet for 32 weeks[1].

At long last: A peer-reviewed report of a truly world-beating endurance athlete who tried a low-carb diet while competing at the elite levels of his sport!

The journal paper doesn't name the athlete, but after reading his listed accomplishments it's not hard to work out who it is.

But before I tell you who he is, I want to quickly mention where he is from.

To Spain, With Love

I have very fond memories of Spain. The food, the beautiful mountains, the bicycle-friendly drivers, the velvety smooth roads, and the way the gorgeous women there don’t just say my name, but practically sing it instead:


And so I’m going to give my Spanish-speaking readers some free advice, without them needing to turn on their translation apps:

No utilices estúpidas dietas de trucos de los países de "Cinco Ojos" (Estados Unidos, Inglaterra, Canadá, Australia, Nueva Zelanda). O cualquier otro país donde la gente están más gorda y menos saludable que tú.

You can thank me later.

Okay, so who is this world-class athlete hailing from the magical land of sangria, flamenco and Rotor 3D+ cranksets who fell prey to a low-carb diet?

Eneko Llanos.

Eneko Llanos is no Instagram pretender whose athletic awesomeness exists largely in his own mind. The 44 year-old Spaniard is a truly world-beating Ironman who not only competes at elite level, but has displayed remarkable career longevity. Despite qualifying as a Masters athlete, Llanos continues to compete and win against elite younger competitors. Eneko is like the Vitor Belfort of triathlons.

Eneko’s resume is pretty damn impressive – he is by far the most accomplished athlete I’m aware of that has competed while following a low-carb diet. According to the International Triathlon Union website, he competed in his first elite event way back in 1995. He competed at the first Olympic triathlon at the 2000 Sydney Olympics, taking twenty-third place; at the 2004 Athens Olympics, he came in twentieth.

It didn’t take long after that for him to rise to the top of his game. He was Xterra triathlon (i.e., cross-country triathlon) World champion in 2003, 2004 and 2009. Over the years, he's won the ITU Long Distance Triathlon World Championships, the ITU Cross Triathlon World Championships, the ETU Long Distance Triathlon European Championships and the ETU Cross Triathlon European Championships. Between 2005 and 2016, he completed 28 professional Ironman (with six victories; 11 top-3 and seven top-8 placings) and 36 half-Ironman (26 victories; five top-3 and five top-8 placings) races.

Suffice to say, the guy’s a machine. Which begs the question: What da fudge was an athlete of his calibre doing trying a low-carb diet?

Tummy Troubles

For 23 years, Eneko had been following a high-carbohydrate, lacto-ovo-vegetarian diet. But in the three seasons prior to commencing a low-carb diet, Eneko frequently suffered from severe gastrointestinal distress. This included difficulties digesting his in-race carbohydrates and fluids, side stitches, and stomach bloating and cramping. These side effects occurred when he competed in full Ironman events, usually after 10–15 km into the 42km run. These side effects did not occur in half-Ironman racing or during training.

After unsuccessfully experimenting with several dietary interventions, such as increasing his carb and fluid intake in training, and manipulating the amount and composition of his in-race carbs and fluids, he decided to try a long-term low-carb/high-fat "adaptation" while maintaining his vegetarian eating pattern.

It's worth noting this nutritional intervention took place "under the guidance and supervision of a sports physiologist with extensive prior experience in LCHF interventions with elite ultra-endurance athletes." The paper, of course, does not say who this sports physiologist is, although I can think of two or three likely suspects off the top of my head.

Eneko started his low-carb diet in mid-October 2016 and strictly maintained it for 32 weeks until the end of May 2017. While following the LCHF diet, his daily caloric intake remained the same as his previous high-carb diet. His daily protein intake went up slightly, from an average of 138 grams to 153 grams. His daily carb intake went from 638 grams to only 52 grams. His daily fat intake, in contrast, went from 98 grams to a hefty 354 grams.

Avoid Carbs. Not.

Despite their constant carb-bashing, sport-oriented low-carb proponents typically recommend increasing carbohydrate intake prior to and during an athletic event – an implicit admission that carbohydrates are crucial for athletic performance.

And so whoever advised Eneko told him to increase his carbohydrate intake in the days prior to an event. This meant eating 125, 150, and 175 g of CHO per day in the 3 days prior to half-IRONMAN events, and 200 and 250 g of CHO per day in the 2 days prior to full IRONMAN events.

He was also advised to consume 60 grams of CHO per hour during the race, largely in the form of waxy maize starch and Gu Energy gels.

Those who issue these kinds of dietary prescriptions are effectively acknowledging a low-carb diet does not negate the body’s need for carbohydrate during endurance events. Instead, the hopeful theory behind this melding of low-carb eating with “targeted” carbohydrate intake is that the increased use of fat as an energy source will at least reduce the need for carbohydrate. By increasing carbs around an athletic event, these prescriptions hope to offset the performance decrements that would otherwise occur on a low-carbohydrate diet.

Wishing and hoping is one thing, what transpires in reality is often entirely different.

Eneko estimated his compliance with the prescribed diet at approximately 95% - something you would expect from a highly-disciplined athlete.

So What Happened?

While following the low-carb diet, Eneko’s training volumes and training intensity distributions were similar to when he followed his high-carb diet. Unfortunately, that did little to stop his race performance from going to hell in a handcart.

Eneko competed in three professional races in 2017 during his low-carb/high-fat dietary intervention: The half-IRONMAN Buenos Aires (March 12, after 21 weeks on LCHF), IRONMAN South Africa (April 2; 24 weeks on LCHF), and IRONMAN Brazil (May 27th; 32 weeks on LCHF).

He finished 18th in Buenos Aires (his worst-ever result in a half-IRONMAN event), 14th in South Africa (his second worst-ever result in an IRONMAN event), and did not even finish in Brazil (he withdrew from the race after 100 km on the bike).


To add insult to injury, after IRONMAN South Africa, Eneko reported the same gastrointestinal problems he had been suffering from in previous Ironman events.

Double ouch.

And to really rub salt in the wound, the diet messed with his mental and emotional state. Eneko reported that the seven-and-a-half months he spent on the low-carb diet were “mentally very tough.” He suffered “many psychic slumps and some feelings of depression.” He reported that the LCHF intervention affected him negatively in his personal relationships; he felt irritable, was often in a bad mood, and overall considered the LCHF intervention “a very uncomfortable experience for his everyday life.”

Ouch to the power of infinity.

The good news is that Eneko woke up and smelled the glycogen. After dropping LCHF like a bag of doggy doo, his performance promptly improved. After resuming his usual lacto-ovo vegetarian high-carbohydrate diet, his next two professional races were IRONMAN Austria (July 1st; 5-weeks off LCHF) and IRONMAN France (July 23rd; 8-weeks off LCHF), in which he finished second and fourth, respectively. Eneko reported feeling much better but not 100% during these events, not surprising given the short gap between these events and his abandonment of the performance-destroying low-carb diet.

On November 18, 2018, almost eighteen months after ending his disastrous low-carb experiment, Eneko pulled off his eighth IRONMAN win at the IRONMAN Arizona.

On July 14, 2019, he pulled off a hometown victory in the IRONMAN Vitoria-Gasteiz.

Things go better with carbs.

Opposite Experience?

When reading through the paper about Eneko, I noticed the author references another paper about "a 38-year-old female professional/elite Ironman triathlete" whose well-being and performance reportedly improved after commencing a low-carb diet.

A world-class athlete who actually benefited from a low-carb diet? Holy cow, maybe unicorns really do exist! I immediately pulled the paper up to see what the heck was going on.

The athlete featured in the paper was an elite female triathlete and doctor[2]. As is par for the course in published papers, the athlete was not named but a quick Internet search reveals the competitor in question was American triathlete Amanda Stevens. One of the paper’s co-authors is Phil Maffetone, an athletic consultant and author based in Arizona, who has worked with Amanda.

Amanda was driven to low-carb eating because of health issues. She presented with 13 years of decreased performances in the IRONMAN triathlon, coupled with “a number of physiological ailments during training and competition over the previous several years. These included severe gastrointestinal distress (vomiting and bloody diarrhea several times during all previous Ironman events), excess fatigue and exhaustion, and severe daytime hunger not completely remedied with adequate energy intake. Menstrual cycles ranged from 33 to 37 days, with significant premenstrual syndrome and dysmenorrhea.”

Amanda had also complained of pain when eating fatty foods, although a cholecystectomy reportedly found no complications. Her fasting blood glucose was elevated (103mg/dl), suggesting issues with glycemic control, but all other laboratory test results were reportedly within normal limits.

Needless to say, this is a pretty shitty state for a dedicated athlete who invests a lot of time pursuing elite performance to find themselves in. After consulting with Maffetone, the decision was evidently made to try a ketogenic diet. Over an initial six-week period, Amanda's dietary carbohydrate content decreased from 73 to 12%, fat content increased from 14 to 75%, while protein levels remained constant at 13%. Her self-reported average energy intake averaged around 2,700 calories per day – around 100 calories less than previously.

When reading the description of Amanda’s health issues, astute readers with a coaching or competitive sports background will have honed in on the mentions of “excess fatigue and exhaustion,” “severe daytime hunger not completely remedied with adequate energy intake,” and menstrual dysfunction. These symptoms literally scream, not “too much carbohydrate,” but “too much training!”

The likelihood of over-training evidently occurred to Maffetone also, and so Amanda’s total weekly training duration was initially lowered from 30 hours to 18 hours (approximately 4h swimming, 8h cycling, 6h running), before a gradual increase in training volume to about 24 hours of total training per week over the subsequent three months.

In addition, overall training intensity was reduced slightly to a mean heart rate of 141 beats per minute, while high-intensity training was discontinued.

What this means is that the intervention to save Amanda’s triathlon career was multifaceted, involving not just dietary but also important training modifications. I’ll get back to the significance of this later.

So What Happened this Time?

Within two months of the training and dietary changes, Amanda reported "increased perception of daily energy during and between training sessions, less perceived hunger and fatigue, and reduced need for daytime naps ... Cycling power increased by 20W and run pace increased (12–15s/km) at the same HR (141 BPM) during training sessions by October 2015.”

Amanda's need to consume food and drink (except water) during long duration training gradually decreased after about eight weeks. Long rides of up to 4 hours at the training HR (141 bpm) power output no longer required peri-workout nutrient supply to sustain energy and power. During longer weekly cycling sessions (up to 7 hours) food intake usually began around hour 4, averaging 100–200 calories/hour. These foods included "applesauce, dried fruit, energy bars, and honey-based fudge, along with a mixture of honey and coconut oil."

By the end of 2015, Amanda's menstrual symptoms had been reduced and by January 2016, her fasting blood glucose was normal (91 mg/dl).

The paper claims Amanda “successfully” competed in three international Ironman competitions during 2015 - in May, August and November. At the Brazil IRONMAN, she was the third female to cross the line. At Coeur d’ Alene and Arizona events, she placed second. In addition, her Brazil and Arizona times were personal bests. Signs and symptoms of gastrointestinal stress, as reported in previous events, were absent.

It all sounds like a huge win for low-carb eating, and that is certainly how Maffetone and his co-author, New Zealander Paul B. Laursen, report it in their paper.

But diets, like diamonds, are forever. And just like a romantic partner, the long-term performance of a new diet often turns out to be a stark contrast to the glowing initial impressions it makes. You guys and girls know what I’m talking about: The charming goddess who devolves into a flabby, whining, shrieking nightmare that slobs around the house in tracksuit pants; the dashing suitor who becomes a fat, farting slob whose increasingly hairy, pale ass becomes mysteriously glued to the couch whenever he’s home:

Oi, Cathy! [THUNDEROUS BURP] Can you grab me a beer?”

Another one? Why can’t you just get it yourself?”

Because there’s a bunch of grown men in tight clothes on TV, running around grabbing at each other under the pretext of chasing an egg-shaped ball - and I don’t want to miss a second of it!!”


Yep, fad diets are just like deceptive romantic partners. They reel you in with the dazzling allure of eternal enchantment, only to deliver disappointment and disillusionment. And gross bodily functions.

So What REALLY Happened?

To try and ascertain the longer term effects of Amanda’s dietary intervention, I searched around online for more recent results. As I did, I discovered a somewhat less rosy picture than that painted by Maffetone and Laursen.

There were a couple of 2015 events they curiously neglected to mention in their paper, one of which was the IRONMAN 70.3 Los Cabos on October 25, where Amanda did not make the podium, finishing 6th among the ten female competitors.

Two weeks prior to that, on October 10, Amanda competed in The Big Cahuna – the IRONMAN World Championship in Kailua-Kona, Hawaii. Unfortunately, she registered a DNF (Did Not Finish) at the event, bailing out after the initial swim leg.

What is doubly concerning about this is that her previous event, the IRONMAN Coeur d’ Alene, was on June 28. That allowed Amanda over 3 months to prepare for the World Championship, so the DNF can’t be written off to residual fatigue from a prior event.

Why Maffetone and Laursen didn’t mention this is a mystery. You’d think Amanda’s participation in the world’s biggest IRONMAN event after going low-carb – for better or worse – would warrant a mention in their paper, but they instead chose to ignore it.

Amanda’s subsequent 2016 season was a mixed bag. Her highest IRONMAN placings were a handful of 5th place finishes which, while certainly respectable, failed to replicate her promising 2015 results in Brazil, Coeur d’ Alene and Arizona. In fact, at the 2016 IRONMAN Arizona, she placed 24th among the 25 starters.

And on September 24, at the 2016 Oklahoma ITU Long Distance Triathlon World Championships, she registered another DNF.

I haven’t been able to find any results for 2017 and beyond, but the Pro Triathlon Stats website indicates limited participation in 2017 and a drop in Amanda’s world female IRONMAN ranking from 34 to 171.

Before I continue, I want to make one thing perfectly clear: This is not in any way meant to be a disparagement of Amanda. She is clearly a dedicated and talented athlete who at one point (2013) was ranked #13 among female IRONMAN competitors. Number 13 at that level of competition is truly world class.

Given the health issues she was facing, the dietary and training changes she instituted in 2015 were born out of necessity, not from wanting to try the latest wanky fad. She apparently instituted these changes, not after reading some bullshit low-carb blog, but after consulting what was ostensibly an experienced nutrition and training specialist.

My issue here is with the 2017 paper by Maffetone and Laursen, and how it mysteriously ignores the less favourable performances from Amanda’s 2015 season. Her lacklustre 2016 season also fails to get a mention. To be sure, peer-reviewed papers can take a long time to make it from submission to publication, but something tells me little effort was made to provide an update on Amanda’s situation, either via the original journal or in other forums.

Last week, I tried contacting Amanda via the only email address I was able to find online, to ask about her experiences after the 2015 season. I have not yet heard back from her.

When the Diet Honeymoon Phase Ends

The pattern seen with Amanda’s triathlon results is not unlike that of other world-class competitors who “successfully” tried highly-hyped fad diets: Initial positive changes, followed by a decline in performance, then retirement from elite levels of competition.

In 2013, low-carb devotees gleefully reported that pro road cyclist Dave Zabriskie (of DZ Nuts fame) had commenced a low-carb ‘Paleo’ diet. No stranger to experimenting with unconventional diets, Zabriskie competed in the 2011 Tour de France on a vegan diet.

Dave Zabriskie

But in addition to his new low-carb 'Paleo' diet, Zabriskie had also begun working out in the gym, as well as doing hill sprints and other forms of high-intensity interval training. His body weight dropped from 168 pounds to 154 while his deadlift increased from 150 pounds to 245. While the owner of the gym where Zabriskie trained gushed about the results as if they were a world first, the fact remains far stranger things have happened than people getting stronger after commencing weight training.

Stronger legs can push pedals harder and faster. Not suprisingly, Zabriskie's training routine increased his power on the bike by around 15 percent.

Men’s Journal reported all this as if it were a byproduct of his low-carb diet, even though low-carb diets have never been shown to increase strength and power. Study after study, however, shows that resistance training is extremely effective for increasing strength and power.

Men’s Journal said Zabriskie performed well in the Volta a Catalunya, an early-season Spanish stage race, before dropping out in the last stage due to illness.” In other words, his first race after going low-carb resulted in a DNF. The research showing carbohydrate restriction in the face of intense activity impairs immune function raises the possibility his new diet and late-race illness were not mere coincidences[3].

The rest of 2013 was a disappointment for Dave, with another 3 DNFs and a DNS among the string of lacklustre results.

After dropping out of the one-day Il Lombardia in October 2013, Dave confirmed the Italian event would be the last race of his 13-year professional career. "I unfortunately had a bad season with the injuries and hardly raced at all."

"My body feels it's the right moment too," said Dave. "My left leg is all crappy. I still feel the effects of the car hitting me in 2003." His body had had enough, an inevitability no fad diet was going to circumvent.

Again, don’t hold your breath waiting for Men’s Journal to publish a follow-up pouring cold water over their initial jubilant story, which featured the likes of ‘Paleo’ author Mark Sisson and Stephen Phinney, the notorious low-carb shill who continues to pimp low-carb diets as awesome for athletes based on his thoroughly discredited cyclist study from decades ago.

Another legendary example of selectively ignoring long-term results in order to pimp a pseudoscientific dietary dogma involves Carl Lewis, who during the 1980s was one of the world’s most famous and successful track athletes.

In an introduction he penned for the book Very Vegetarian by Jannequin Bennett, Lewis claims to have commenced a vegan diet in July of 1990. By early 1991, Lewis was feeling listless and wondering if he should add meat back to his diet. After consulting with vegan author Dr John McDougall, Lewis instead decided to increase his caloric intake and says he felt much better. "And I had my best year as an athlete!", exclaimed the multiple gold medal winner[4].

Enter that last quote into your favourite Internet search engine and you’ll see it has been eagerly repeated ad nauseum by vegetarian and vegan devotees.

But it doesn’t even begin to tell the full story. Lewis did indeed have an outstanding year in 1991, breaking the 100 metre record in Tokyo and triumphing over rival Mike Powell in an epic long jump showdown.

After 1991, however, Lewis' dominance in the sport promptly began to wane. After setting a 100m world record the previous year, he failed to even qualify for the 1992 Olympic team in the 100m and 200m events. He did qualify for the long jump and 4 x 100m relay, winning the first and setting a record-breaking pace in his leg of the latter.

At the World Championships in 1993, he finished fourth in the 100m, and did not compete in the long jump. He took bronze in the 200m, which would prove to be his last ever Olympic or World Championship medal in a running event.

Lewis was then sidelined with injuries for the next few years. He made a comeback in 1996, qualifying for the long jump at the Atlanta Olympics. While he couldn’t match his past performances, he managed to take gold ahead of his main rivals Mike Powell and Iván Pedroso, both of whom were nursing injuries.

Lewis retired from competition in 1997.

It reeks of pro-vegan bias to attribute his sterling 1991 season to his vegan diet, but to insist that same diet had nothing to do with the performance decline that promptly followed.

Likewise, it reeks of pro-low-carb bias to hail someone's initial positive performances as being due to their new low-carb diet (when they may have in fact been due to weight-training or much-needed reductions in training volume), but then blissfully ignore the performance decline that followed.

Like Amanda and Dave, Lewis was at the tail end of his career when he radically changed his diet. Age eventually slows down even the most gifted of athletes. Interestingly though, when asked about the stark contrast in his performances in Tokyo and at the selection trials for the Barcelona Olympics, Lewis himself replied: "Everyone's saying, 'Oh, he's old now. But I ran my personal best 10 months ago. The likelihood of me diminishing that much in 10 months from age is ridiculous."

If it wasn’t age, then …

A Fad is a Fad is a Fad

In Eneko’s case, the results are clear: A low-carb diet destroyed his athletic performance.

Amanda’s case is complicated by the fact she was evidently over-trained and would have benefited from a reduction in training volume, irrespective of what dietary changes were also instituted. Thus, we have to wonder whether the dietary changes helped or hindered the benefits attained from cutting her hefty training load.

One thing I immediately noticed was that, in order to accommodate her new low-carb training regimen, Amanda was instructed not to push her mean heart rate beyond 141 BPM. Running a quick back-of-napkin calculation using the old 220-minus-age formula, this suggests Amanda wasn’t allowed to exceed 77% of her maximum heart rate during training. While this would have been a suitable limit for much of her training, there are times when an athlete needs to drop the hammer and push the limits in order to extract further improvement. With a recommendation like this, HIIT-style training would have been essentially off-limits for Amanda. Indeed, she was explicitly told to avoid high-intensity training.

I don’t see this as a solution, but a temporary band-aid. Imagine telling your mechanic that your car engine became very noisy and caused your car to vibrate disconcertingly every time you exceeded 80 km/h. You would expect him to book your car in for an inspection so he could diagnose the problem and fix it, right?

What you would NOT expect him to do is say, “Well, don’t drive your car faster than 80 km/h then!”

One last thing I’d like to add is that a low-carb diet did not seem to have quite the same negative long-term impact, in terms of placings, on Amanda as it did for Eneko and Dave. One possible reason is that women utilize a higher percentage of fat during exercise when compared to men[5]. As a result, low-carb diets may not suck as much for women as they do for men when it comes to athletic performance.

Perhaps the best that can be said is that Amanda’s experience shows female athletes can follow a low-carb diet while competing in prolonged endurance events like triathlons. They won’t blaze ahead of the field, but – in between inevitable DNFs - they may be able to at least hang with the pack and maybe even score a few podium finishes. They may thus be a last resort option for someone who has truly exhausted all other options for remedying their ‘carbohydrate intolerance.’ And I do mean exhausted – there are numerous options for dealing with gastrointestinal disturbances and disturbed glycemic function aside from the throw-the-baby-out-with-the-bathwater strategy of avoiding carbohydrate. These strategies can range from avoiding high-sucrose sports drinks like Gatorade in favor of drinks using glucose polymers and glucose/dextrose, using probiotics and other gastrointestinal-friendly items like aloe vera, to checking for underlying issues such as ulcers, celiac disease, IBS, etc.

When recommending low-carb diets to athletes, and when discussing these diets in publications read by coaches, nutritionists and athletic consultants, they should come with a clear warning that such diets have a poor competitive track record to date, are associated with a high rate of DNFs, impair performance at high exercise intensities, and have consistently returned inferior results in scientific comparisons with higher-carb diets.

Update: On 18 November 2020, I received an email from Amanda Stevens, who kindly replied with the following:

Hi Anthony,

How are you? Apologize for the delayed response.

Yes, I am the athlete in the case study.

Answers below....let me know if I can help out in any other way.

- Are you still competing, and still following the LCHF diet?

--> Not currently competing. I finished my medical residency in July 2020 and am in a sports medicine fellowship currently. I had two kiddos during residency, so my racing was placed on hold. I still workout, but am not specifically training for anything. I do still follow a LCHF diet.

- If not, how long did you continue to compete while on the LCHF diet?

--> From the time I started working with Phil until my last race prior to starting residency I was training/competing LCHF.

Were you able to replicate the initial positive performances reported in the paper?

--> Yes, and saw even more improvements. I am also a coach and see improvements across the board for them as well.

- Were there any negative effects? I'm thinking here of performance at higher intensities, sprinting, etc.

--> With MAF training, the majority of training is done at or below your aerobic threshold. I think the two things go hand in hand, your nutrition has to support your training and your training has to support your nutrition. This is especially true when you are trying to maximize performance without detrimental effects to your health. There were short bursts of efforts in training and racing and I never felt like these were compromised. Again, we would appropriately support these with nutrition and recovery.

When it comes to LCHF there are many nuances. I believe in a whole food diet that is nutrient rich. Macronutrient balance should fit the individual and their activity/training, cookie cutter doesn't work very well in my opinion. And I'm also not a fan (as in I don't eat/use or recommend to my patients or athletes) any sugar substitutes or keto 'fad' foods.

My experience with LCHF has been transformational!

My further comments: Clearly, Amanda's experience has been a stark contrast to Eneko's. Again, I suspect this may be due to the fact women burn a higher proportion of fat as their fuel source during exercise than men. Also, Amanda acknowledges LCHF eating may affect performance at higher exercise intensities, and has adapted her training accordingly.

I'm also heartened to see Amanda is pro-whole foods, against cookie cutter programs, and not into fad foods or shady sugar substitutes.

While I'm not a fan of low-carb diets for athletes, if one is determined to try this approach or has health issues that may warrant a trial of this approach, I'd much rather they consult with someone like Amanda than some hare-brained diet 'guru' or social media 'influencer.' Those interested in hiring Amanda for consultation can contact her at:

triusa [at]


  1. Mujika I. Case Study: Long-Term Low-Carbohydrate, High-Fat Diet Impairs Performance and Subjective Well-Being in a World-Class Vegetarian Long-Distance Triathlete. International Journal of Sport Nutrition and Exercise Metabolism, May 1, 2018; 29 (3): 339-344.
  2. Maffetone PB, Laursen, PB. Reductions in training load and dietary carbohydrates help restore health and improve performance in an Ironman triathlete. International Journal of Sports Science & Coaching, 2017; 12 (4): 514–519.
  3. Pedersen BK, et al. Training and natural immunity: effects of diets rich in fat or carbohydrate. European Journal of Applied Physiology, May, 2000; 82 (1-2): 98-102.
  4. Bennett J. Very Vegetarian. Thomas Nelson, Nov 8, 2001.
  5. Devries MC. Sex-based differences in endurance exercise muscle metabolism: impact on exercise and nutritional strategies to optimize health and performance in women. Experimental Physiology, 2016; 101 (2): 243–249.


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