How to win the Ironman on LCHF


Bevan McKinnon deep into the Ironman marathon and looking very very strong on LCHF

Bevan McKinnon, aged 43, just smashed the age group field at Ironman NZ.  He set a personal best of 9.00.59.  Not bad for an old guy with 8 weeks of specific preparation.  Here I report back on an interview I’ve just completed with Bevan.  We have been working with Bevan for a couple of years now at AUT Millennium in our high performance labs, trying to understand how we can tweak the LCHF approach to become a fat burning machine.

Click here for Bevan’s full race results.

I’ve previously written about Bevan’s 2013 Ironman NZ preparation. We had great lab performance data (moved form 130 W to 300 W power output for a 50/50 carb and fat fuel use), but were a couple of tweaks off converting that into a stellar race performance. Bevan was leading last year throughout the bike and faltered on the run with severe cramping.  After assessing what could have been contributing factors in the onset of cramp, Bevan altered his race nutrition plan this time to include more electrolyte and grams of CHO per hour than he’d consumed in 2013. This nutritional tweak was a small but significant change.

Back to 2014 race day:

Swim: 3.9 km 51:53
Bike: 180 km 4:58:36
Run: 42.2 km 3:04:11
Overall: 9:00:59

First age grouper home by almost 15 mins, and inside the top ten including all pro athletes.  Even better were his run splits which were incredibly consistent and Bevan never came close to running out of fuel.

Run Details Division Run Leader | Division Rank: 1

Split Name


Split Time

Race Time


Div. Rank

Overall Rank

Gender Rank

7.4 km 7.4 km 31:22 6:28:10 4:14/km
14.2 km 6.8 km 28:29 6:56:39 4:11/km
21.3 km 7.1 km 30:04 7:26:43 4:14/km
28 km 6.7 km 29:51 7:56:34 4:27/km
35 km 7 km 32:13 8:28:47 4:36/km
42.2 km 7.2 km 32:12 9:00:59 4:28/km
Total 42.2 km 3:04:11 9:00:59 4:21/km 1 9 9

OK, he’s a really classy athlete and was anyway.  But LCHF and fat adaptation have taken him to a whole new level. Here’s the full story….

Training preparation

“I started some focused Ironman build up after Xmas.  We went to the States for a holiday, and it was early January. Obviously I was fit anyway, but nothing specific in terms of Ironman preparation.”

So what did training look like?

“On a couple of weeks I got up to about 25 hours of actual training.  I was swimming sessions up to 5000 m with 18-20 km a week of swimming.  I knew I had to get that amount of swimming in to get to the low 50 min mark for the Ironman distance.  Biking included a long aerobic ride.  I did end up biking to Tauranga to watch the Port of Tauranga Half (a 280 km ride). I would do a weekly “sweet spot” ride on the bike, usualy mid week.  Running wise, all of my running was aerobic, and I never ran more than two hours in any one session.  In saying that, I did do a week where I did two by two-hour runs. That said, I did include three or four threshold type runs in the whole preparation. These were on a grass track typically 40 min workouts, say 8-10 by 800 m with 200 m float in between, and only when I was feeling fresh enough to do it.”

When you look at Bevan’s Training Peaks data, he is very careful about recording and watching his output. He was quantifying his weekly work in daily “critical training load”.  This is the TSS (Training Stress Score) score and he was at around 150-160 TSS a day.  This is qute a big load.  Remember, a TSS of 100 is the equivalent physiological demand of a 1 hour time trial. He maintained that on most days for 6-8 weeks, with some periodisation for rest of course.

Heat chamber: Bevan used the heat chamber at AUT Millennium to develop some heat adaptation and increased blood plasma volume during the taper phase leading into IMNZ.  He says “I think this was also key as I was about 5 bpm down heart rate for the same power output after the heat training.” Heat training is known for these effects in increasing blood volume and reducing viscosity.

Training take homes: This was not a minimalist training approach.  Bevan trained long and put in some very big weeks. The demand was high, but the output carefully monitored on Training Peaks.  When his output dropped off, he recovered. Recovery and adaptation is how you improve.

Diet preparation

Bevan has been on a low carb high fat diet since November 2013. I think that is important as my feeling is now that longer-term adaptations are required to make the full shift and to optimise benefits in metabolic efficiency and fat burning.  His diet is typically three reasonable meals a day with protein from animal sources usually along with a very high vegetable intake.  He uses coconut oil, olive oil and butter as his major extra sources of added fat. He avoids industrial seed oils high in Omega 6.  His diet  is high in fish, eggs and nuts.

Leading into the race there was no special carbohydrate loading or any particular change in diet, apart from some extra kumara (New Zealand version of a sweet potato) in the few meals prior to race.

  • Dinner the night before: Roast pork with crackling, vegetables, kumara
  • Breakfast: Small amount of high fat yogurt, banana, protein powder.


“One great thing about LCHF is my new found ability to get my weight under 80 kg” says Bevan “I’ve always trained quite a bit, and never ever been able to get my weight less than about 82 kg.  That’s just too heavy for Ironman racing, especially the run”

In other words, this diet allowed Bevan to get to a race weight aligned to actual high performance Ironman racing for the first time in his triathlon career. It is interesting that he was unable to get near this weight previously despite training up to 30 hours a week.

Race day nutrition

Here’s the big change made. The race fuel wasn’t fat, it was 20 gels and 1.5 bottles of coke on the bike leg.  On the run he started with a handheld gel bottle holding 4 gels.  At the halfway he collected another bottle but ended up not using that and went to a combination of coke and water after that.

Remember as you read below that carbs, especially in the rapidly absorbed form such as gels, boost blood sugar and insulin production. Insulin turns off fat burning and promotes glucose burning.

Bevan had discovered, for himself at least, that once he was well fat adapted, that when he was riding at around 270 W power output then the extra gels didn’t end up dialing down his fat metabolism.  He was still around 50% fuel by fat and 50% by carbohydrate. We feel that the whole Kreb’s (fuel) cycle in the body was spinning fast enough and fuel utilisation was high enough that insulin wasn’t being secreted in massive amounts to dial down fat burning and promote glycogen only fuel use.  This isn’t what you see in non-fat adapted athletes.  Nor is it what you would see in Bevan at rest. This was a key discovery as he could get the performance benefits of the carbs whilst still maintaining the fat burning that he had developed through his LCHF and mainly fasted long aerobic training work.

Bevan never really practiced using that amount of carbohydrate on any of his build up simulations.  Only in a practice half ironman in January did he do the same thing (he won that race too).  Many sessions were fasted or with no food.  Train low, race high?

Take home: Bevan at least can tolerate quite a lot of carbs during the race (600g or 2400 kcal on the bike).  This didn’t dial down fat burning for this fat adapted athlete.  This maximised his performance.  It probably didn’t do his health any good for the race day itself. That’s probably because of the oxidative stress he put himself under, but I’m not thinking Ironman racing is a health kick.

The race itself

“I just felt strong the whole way” says Bevan “I got off the bike after doing 170 of the 180 km solo and my legs felt brilliant.  I just started running and felt I could keep it up for the whole marathon so away I went”.

This is fabulous, as anyone who knows the Ironman New Zealand bike course – it has mostly gradual climbs, usually a headwind on the two return legs from Reparoa (strong winds this year). Bevan describes the road surface as a “cheese grater ride”.

“I had no “dark moments” at any stage in the race.  I had enough fuel to simply keep going.  In the end I was suffering some minor muscular soreness on the ups and downs of the run course which slowed me slightly. I wasn’t aiming for a specific time, and it wasn’t until the last seven kms that I realized I had the chance to go under 9 hours, which I just missed out on in the end” says Bevan.

Bevan ended up even stopping during the bike ride to go into the toilets and have a pee.  Frankly I was astounded by this, as any triathlete of this level usually just “goes on  the run” so to speak.  So there’s a couple of minutes that might have pushed him under the 9 hour mark.  Who knows?

Overall take homes:

  • The LCHF nutrition approach is feasible for high performance endurance racing including Ironman
  • The application at this level  requires carbohydrate ingestion during the event itself
  • Carbohydrate loading wasn’t necessary
  • Heat chamber training may have been beneficial for performance
  • Monitoring training load and output during training and racing was useful, especially power on the bike.
  • The low carb lifestyle is something that Bevan has been able to maintain and he does so during his regular working and coaching life regardless of the performance benefits.  He has suffered hyperlipidemia to the point his doctor was recommending medication on his high carb athlete diet previously.  These issues, especially around triglycerides, have resolved with the LCHF approach.

Finally congratulations.  This was an astonishing effort. AUT and our high performance team are proud to have been involved.  That said, it was Bevan’s drive, work ethic and attention to detail which made the real difference.
Our athlete and nutrition services are available to the public. Click here for athlete clinics, email us for nutrition.

Bevan’s coaching website click here. his own race report here

46 Comments on “How to win the Ironman on LCHF

  1. Pingback: [Fan Club] LCHF Lifestyle - Part 2 - Page 656 -

  2. Hi Grant – these results are awesome. I started lowering carb and increasing fat back in Sept last year, initially with great results. But as the training grew and I reduced carb further (not measuring but got quite low) I ran into a number of problems:
    – much higher levels of fatigue / slower recovery
    – lack of “punch” for harder efforts across all 3 disciplines
    – inability to raise heart rate much when cycling
    – extreme cold sensitivity – got really cold when swimming open water even at the peak of summer, coming out of any swim into cool air left me painfully cold and needing blankets / hot water bottles, and on cooler or windy days the wind chill when cycling meant I had to wear many extra layers when others didn’t.

    Thyroid function (amongst other standard blood tests) was checked and all was apparently ok. What I did discover was a couple of times when I ‘fell off the wagon” and had a day or two of my old higher carb eating patterns many of these symptoms disappeared.

    One other thing I realised late in the piece is that I hadn’t upped my salt intake much as I understand perhaps I should have, but would this be responsible for such symptoms?

    Did I go wrong somewhere with how I was doing LCHF, or maybe I just need a higher carb (or at least more carb in my) diet?


    • Yes great questions and not the first time I have heard most of these. Let’s work through what we can find some answers, or at least there may be options for

      much higher levels of fatigue / slower recovery
      – lack of “punch” for harder efforts across all 3 disciplines
      – inability to raise heart rate much when cycling
      – extreme cold sensitivity

      I think all of these are probably related to same overall issues. Yes salt and lack of (you probably need about 5 g a day to start) could help. But I think the more likely solution is that training intensity needs to match the fuel availability. In other words, you have to train in th fat burning zone for the bilk of your training. This i virtually impossible in my experience when you are out with a bunch of other athletes and testosterone is involved, especially on teh bike. Even more so when hills are involved. Bevan trains on the wind-trainer with his intensity in mind most of the time.

      You cannot train the same way you did on a high carb diet. Teh best thing is that if you cahnge training you will be burning fat which won’t damage you metabolically like the oxidative stress of carb burning.

      You can match carbs to the workout and remain low carb. But match the requirements the session to the carbs you eat before and during.

      Lack of punch and high end – yep – that is down. Lucky Ironman doesn’t require this energy system.

      Cold sensitivity – tells me you have zero carbs on board and can’t find glycogen anywhere. So I think the combination of LCHF, too much intensity and not matching carbs to specific sessions is likely the major issue.

      Comments anyone else?

      • Fully agree. Since I train with the Maffetone method (= just below FatMax intensity) I recover beautifully and not only can train every day – I want to train every day. But it is initially very slow, especially if you are not fat adapted. I don’t know many who can actually do it. But those who do and stay with it reap the rewards. Needs a lot of trust though.

  3. Thanks for this report – really interesting stuff. Can you expand on the use of the heat chamber? Does training happen within it? What are durations? What are average temperatures & humidity?

    • Yes we set up the bike in a large chamber which we cn control the temperature and the humidity. I think its typically aroudn 32 C with 85% humidity. Ride ont he wind-trainer for about an hour several times.

  4. Nice. Next step is to get him dialed into LCHF for the race itself and then you have the ultimate healthy endurance machine.

  5. Nice. Next step is to get him on a high fat low carb intake for the race itself, and then you have the ultimate healthy endurance machine!

  6. A couple of questions
    1) during the bike and insulin rises you speak of, would they likely be almost a non issue on race day due to the alternate exercise controlled pathway of glucose into cells?
    2) physiology with the innability to completely burn triglycerides in the absence of carbs? Out of date or is it more about insuring there is still some carbs present in the system for this?
    3) carb loading vs no carb loading for the race? Would be interesting to do a muscle biopsy on someone adapted to see what muscle and liver glycogen levels are pre race to see if there was a benefit to carb loading still.

    • Interesting: I think some studies ave shown that insulin can rise during exercise and shut down fat burning see but we just didn’t see this effect with a fat adapted athlete

      Regarding glucose in the body – the body always has some (homeostatic) glucose – from various sources it can and will scavenge it – otherwise you’d die which would be a poor adaptation really. So I think there is always enough glucose around for these sorts of functions

      Carb loading or not? – yes that would be interesting – not sure who would volunteer for the biopsy, but it is also possible that a few large carb loads would unapt you to the fat burning. More research needed.

      As usual, incomplete and developing science – run away form anyone who claims to know everything about nutrition

      • The brand new FASTER Research project found out that the LowCarb athletes had the same amount of glycogen in their muscles after a 3h run as the HighCarb group. They also oxidated 2.6x the fat during the exercise. So low carb athletes still refuel their muscles fully.

  7. Thanks for that Grant. Have suspected that it may rise during exercise as I often get a flat patch 5-10minutes after consuming a gel in training and wondered whether it was due to that. 25g bolous of carbs is probably not the ideal way to administr on an empty gut. Doesn’t seem to happen racing when the stomach is loaded to close to the max it can handle.

    Mitch anderson (former ironman west oz winner and doctor) used to be into training fasted and consuming nothing for the first hour to boost fat burning rates.

    The question I guess to pose with the carb loading would be two fold 1) amount of glycogen stores for the fat adapted athlete post taper/pre race vs carbo loaded and 2) 36/48h carb load protocol vs non loaded fat adapted for lipolytic enzyme activity/fat burning rates.
    It’s also such a pity ironman is not reproduceable with performance to run cross over.

    All interesting stuff thanks

  8. Excellent article. How was “aerobic” zone determined? Maffetone calculation, zone 2 based on max HR or some type of RQ measurement?

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  10. As a 42 year old triathlete / runner, I was very interested to see this post. There is not a lot of recent data regarding whether or not LCFH endurance athletes consume carbs during races. I have just started an LCHF diet (12/26/13). I did not do this to improve race performance, my motivation was health related (My triglyceride to HDL levels are way out of whack and my LDL’s are very high). I will say that rather than getting in a debate with anyone on this forum about the wisdom of eating bacon & eggs almost daily for breakfast when one has high cholesterol – I will simply refer you to the book “Cholesterol Clarity – what the HDL is wrong with my numbers” by Jimmy Moore (I’m not affiliated with him, nor is this a link – I don’t benefit in any way from the mention here).

    I was very concerned with the effect that cutting out the carbs (pasta, bread, power bars and sports drinks) would have on my athletic performance. I have been pleasantly surprised! My running has improved massively – I only drink water on long runs – and my recovery is much quicker. Water only has been fine up to 14 miles (my longest run yet).

    I will continue to run with only water – and see if I “bonk” at any point. If I do – I will add in some sort of race nutrition and see how that helps.

    Did I read correctly that Bevan did not practice adding in the carbs while training? That would be very un triathlete like as practicing nutrition is part of any training plan. Would be pretty risky to add in the GU’s and coke on race day.

    Also – do you know of any other cases of triathletes or long distance runners that you know use some sort of carbs on race day? If so – any idea of how much? I plan on experimenting and comparing while training this year, but any info would help me with a starting point.

    Thanks again.

    • HI Chad

      Your story is my story buddy.

      Check out my planned experiment with a 50k race this weekend. Going to try RACE DAY carb consumption even though I don’t use carbs during training – I have run 32k on water only and I have been fine.

      I did race a 30k the other day and had my first Coke / Gel at 25k – I gather that high intensity effort requires a carb ‘top-up’ after a while; and it made a noticeable difference (in a good way).

      I’ve tried all sorts of iterations – like gorging on carbs three days prior to a marathon and found I feel heavy when lining up. I’ve fasted, then carbo loaded etc.

      This weekend I’m running 50k and will stay strict keto – only on race day have something easy on stomach, and carb during the race. Still a bit chicken to try 50k on no carb at all.


      • Gary – how did the race go? How many carbs / sugars did you consume during the 50K?

        Eagerly awaiting your report.

  11. hey grant, just on this LCHF lifestyle whats your thoughts on someone who has there gallbladder removed ?

  12. This is great info. I am on LCHF – in fact ketogenic so really LCHF – and I run marathons. I have experimented with upping carb intake prior to races, but I feel ‘heavy’ and sluggish in the days before.

    I am running a 50k (a race called Om Die Dam) and after reading this I have decided to experiment a little differently – so I’ll stay LCHF right up until race morning. On race day I’ll drink an electrolyte energy drink and for the race will take some gels, and I’ll eat bananas and alternate between water and coke (water points every 3k – so coke every 6k).

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  14. Hi Grand, nice article with usefull info.

    Lately i have measured up to 2.2 ketones level in my blood and i suppose that i am fat adapted :)))

    I training aerobically using the 180 formula (basically: 180-age=maximum aerobic function heart rate). I am 45 and do my workouts in the heart rate range of 125-135.

    My questions are: now that i am burning more fat for fuel is this formula still valid?. How can be defined the heart rate point from which my body starts producing energy using anaerobic metabolism? When an athlete is fat adapted this point moves higher or stays the same?


    • Well done on the ketosis – interesting question you won’t know the answer to unless you did a test on our gas analysis gear. Most likely there will be a big shift in the heart rate you burn fat at – but easier aerobic will still be the place to be for longer work. I would stick with the same formula – its a safe bet you are just burning more fat at the easy aerobic pace

    • Hi Nikos, a bit late but I had the same story and same question. I did a VO2MAX test and it turned out that my FatMax HR was about 7 beats higher than my Maffetone rate. Did three sessions on the higher rate and felt really tired. It really affected my recovery. I remember Maffetone insisting to stay on the same rate no matter what in his book. On the other hand, his assistant on his web-page said that the Maffetone formula aims for the FatMax point. I think I just put it down again a bit and find the highest HR that still is great with recovery.

  15. Great post. I’m left with a few questions:
    Wondering what his general carb intake was on a daily basis (~30 grams?) and during training?
    Did I read correctly that no supplemental carbs were used except on high intensity running days? I’ve been doing HFLC for a while now but have yet to dial in the appropriate daily and training carb volume. I often will train fasted or without supplemental fuel up to 2 hours, but am wondering if I should bring along HF sources for efforts lasting longer than that (e.g. 3 hour rides, 2 hour runs or the long brick workouts).
    What constitutes a hard run from a fueling standpoint?

  16. Very useful post!

    I am a runner. I have been LCHF for almost a year (emphasis on meat, fish, dairy, eggs, nuts, raw veg). Immediately I felt much better, I lost a few pounds and felt quicker and sharper. Only drawback was that I felt the onset of fatigue quicker in the later stages of races. This problem has eased over time. In fact now I find that increasing carb intake for races just leaves me feeling sick post-race so I have pretty much stopped.

    However I am confused about fuelling up during longer events. I have got this wrong a couple of times. I had a 6 hour race a couple of weeks back and one sugary oat bar and a banana after four hours did the trick. I have a 24hr race (fairly low intensity) coming up and am wondering if you have any advice for fuelling up over the 24hours?

  17. Great article and useful insight especially on the high carb intake during race on backdrop of fat adaptation. I did similar thing. Went LCHF six months out from first attempt @ Ironman (i.e. Cairns 2014). Averaged between 10-12 hrs/wk in 3 months lead up. Ended up doing 9:58, which I was pretty happy with and used pretty high carb intake during. Went on to totally reformulate my existing sports supplements I sell ( and have also blogged about my experience going LCHF in prep for Ironman. We’ve just released a new ‘Keto Gel’ – low in carb and with added fat from coconut oil & MCTs. Keen to get some feedback from fellow LCHF on these in anyone interested in trying.

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  20. brilliant thank you
    One thing that did stand out to me about the closing note in the article discussing Bevan’s experience and this was that his blood lipids were above normal previous to his low carb high fat diet (and resolved since). This would make me wonder does he have a tendency to insulin (sensitivity) issues and metabolic syndrome and that he is a metabolic type that will do better with less carbs in his diet. Just as many with insulin problems will fare better on a Banting diet. This is not most “normal” athletes.

    I think there are many fascinating Qs that we are seeking As for in relation to the Carb Vs Fat debate… I wrote some of my thoughts here . I think in summary… there is a continuum of athletes that require a spectrum of macronutrients for optimal health and performance.

    thanks a million for this brilliant article and keep up the good work I will be following 🙂

  21. Hi Libby!

    Do you have to go into ketosis in order to lose weight? I started reducing my carbs last week (started off around 55-58 grams) and this week I dropped it to 33 grams.

    I had did this program before and LOVED it, but my blood sugar would keep dropping, even though I took magnesium and potassium faithfully and drank salted broth. I was previously eating around 20 Net carbs day.


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  23. Hi Prof. Grant. I love this article… I’m always referring back to it! What did Bevan eat directly after training to stimulate quick recovery?

  24. Hi Prof Grant

    I was wondering what Bevan ate directly after a long training session to facilitate quick recovery.

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