Cyclical Ketogenic Diets and Endurance Performance
Question: I’ve seen the idea kicked around that a cyclical ketogenic diet might be beneficial for improving endurance performance. Do you think this is possible and, if so, what’s the best way of going about it.
Answer: This is one of those long-standing questions that’s been on my mind for years and the short answer is ‘maybe’. Some of it depends on what you’re talking about which will make more sense when you get to the end of my answer.
The idea of fat adapting endurance athletes has been around for years, I presented most of the early data in my first book The Ketogenic Diet. Summing that research up, the general consensus was this:
- In the short-term (a few days to about a week), low-carb diets tend to destroy performance.
- With sufficient adaptation (usually 3+ weeks), there may be performance benefits.
But even #2 is a bit questionable. In the most often cited study (by Phinney), the results were skewed by one of the five cyclists who got massive improvements in endurance, the other four stayed about the same. So although the average performance improved, most of the subjects showed no improvement.
The results also depend on how performance is actually tested. If endurance was tested at lower intensities, performance sometimes improved. When researchers tested high intensity activity (where glycogen is required for optimal performance), performance was invariably worse. The conclusion was simple, no amount of adaptation to low-carbohydrate/ketogenic diets would benefit high-performance activities.
This led to the idea that perhaps fat adapting was most beneficial for ultra-endurance types (who typically go at a lower intensity for longer periods) and less valuable for endurance sports where high intensity efforts were required (think of a cyclist who may have to cover a breakaway or make a final sprint).
This also led to a second, more recent data set which was an examination of short-term fat adaptation (5 days) followed by a 1 day carb-load (looks just like a cyclical ketogenic diet). The idea was to get some adaptations in fat utilization AND refill muscle glycogen to support high intensity activity.
Research had shown that many of the adaptations to low-carbohydrate diets hang around for a while (at least a week) after carbohydrates are re-introduced so it seemed possible that the benefits of low-carbs could be generated while refilling muscle glycogen to sustain high-intensity performance.
And the data was mixed as hell.
On average, performance didn’t generally improve which led to the conclusion that the approach was still invalid. However, in the studies that showed individual data, a pattern emerged that I found interesting. The subjects who got the best performance on carb-based diets showed the biggest decrease on the fat adaptation diet. But subjects who did relatively poorer on high-carbs usually got a performance boost on the with fat adaptation.
This is very consistent with my experience with dieters (as discussed in the article series Comparing the Diets, on this site). Individuals who do best on carb-based diets often do very poorly on low-carb diets and folks who do poorly on high-carb diets often thrive on low-carb diets.
Related to this, there is data suggesting that people differ in how well they adapt to increases in dietary fat, some seem to do a better job of increasing fat oxidation compared to others and I suspect this explains some of the difference here. The subjects whose bodies ‘run better’ on fat may be the ones getting performance improvements from fat adaptations.
However there was another problem with those studies, they invariably tested exercise in a way that wasn’t exactly analogous to typical racing situations so applying the data to real-world performance was difficult.
In a very recent study, cyclists followed 5 days of fat adaptation with 1 day of carb-loading and then performed a time trial. The difference was that the time trial included several short sprints (this was meant to more closely mimic a true competition). Power output during the sprints was lower after the fat adaptation even after the 1 day carb-load and despite the refilling of muscular glycogen.
It appeared that the body had temporarily lost the ability to generate energy from carbohydrates quickly enough to sustain optimal power outputs during the sprints. So for the most part, it doesn’t look like a cyclical keto diet can really enhance performance, at least not those requiring high intensity bursts in the short-term.
However, there’s another way that cyclical ketogenic diets might be beneficial for endurance athletes but it has more to do with training than competition. Increasing amounts of data are finding that training and diet interact in terms of the adaptations seen. What you eat on a day to day basis as well as around training affects what sorts of overall adaptations are seen.
For example, early data had shown that several days on low carbs with endurance training increases gene expression for pyruvate dehydrogenase (PDH) which is a key enzyme for energy production in skeletal muscle.
More recent data has examined a molecular energy sensor called AMPk (adenosine monophosphate kinase) which turns out to play a crucial role in endurance adaptations (you can read more in AMPk: Master Metabolic Regulator). AMPk is activated more easily when glycogen is depleted which might mean higher levels of gene expression for the adaptations that endurance athletes are looking for.
Based on a variety of data, it looks like training under conditions of glycogen depletion may enhance endurance adaptations and a theory of training with low glycogen and competing with high has been advanced by some researchers in the field.
The problem is that gene expression and protein synthesis aren’t the same thing and protein synthesis tends not to proceed very well when cellular energy state is low (as would occur when muscle glycogen is depleted and AMPk activity is high).
Which brings us back to cyclical ketogenic diets. What if someone combined glycogen depletion with a large volume of low- to moderate-intensity endurance training; in theory this should generate a great deal of gene expression for stuff important to endurance athletes. However, this wouldn’t be the optimal situation for actual protein synthesis.
What if now that person swung into high-calorie/carb-loading phase with a reduction in training volume (and perhaps an increase in intensity) so that there would now be sufficient energy to synthesize mitochondrial and energetic proteins?
Would this help drive adaptations further than training under normal carbohydrate intake conditions? I don’t know but that’s sort of the idea I’ve been kicking around anyhow.
Basically, although it doesn’t look like a cyclical ketogenic diet is optimal for overall competition results it might be used during a base training phase in an attempt to drive adaptations higher than they’d otherwise go.
During the competition phase, higher intakes of carbs make the most sense based on the most current data, at least for sports which require bouts of high intensity performance during the event (if you’re an ultra runner or something, fat adaptation may work just fine).
Finally, it is at least worth noting that the current kings of endurance running (the Kenyans) are known for exceedingly high daily carbohydrate intakes (70% of total calories) although they are also known for doing consistent morning runs fasted as well as multiple training sessions per day. So they may have actually stumbled on a training pattern where they get the benefits of everything I’ve talked about, some training done fasted/under glycogen depleted conditions with sufficient carbs/calories to sustain optimal rates of protein synthesis.
Of course, since most can’t train three times per day, it’s debatable how relevant that is to the average trainee. A cyclical low-carb approach might be a more practical way of achieve some of what I’ve talked about and I’d love to hear from anybody who’s tried it.
Given that elite marathon runners race at about 80% VO2MAX, deriving almost all energy from glycogen and exogenous carbohydrate, I agree that CKD should be confined to the base training phase.
A middle-of-the-pack marathon runner racing at about 65% VO2MAX might benefit though. The higher perception of effort from training on depleted glycogen stores would also tend to keep intensity in check during long runs and easy training sessions. Any higher intensity work might follow the weekly carb-up, as Lyle has outlined elsewhere. “Keep the hard days hard and the easy days easy.”
Played rugby for a season on a CKD.
Training sucked. Games were in a carbed up state and my game fitness was very good. Dropped alot of weight, one of those situations where I wasn’t eating enough during the week to maintain. Typically I’d be down 20#s by the end of the season. When using a CKD, I was down 40#s, and it was during this time period when I last dropped below a bodyweight of 200#s.
What is the composition of the IMTG’s (medium chain, long chain, saturated, unsaturated, etc)?
Would enriching the diet in a particular fat favor repletion of IMTG stores after endurance exercise?
I gather IMTG composition is varied and reflects dietary intake.
IMTG’s depleted by 2 hours treadmill running can be repleted within 24 hours.
One study found repletion was no faster in trained vs. untrained subjects.
So far as I know, IMTG will reflect dietary intake in terms of type.
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Two comments- there’s a local MD who focuses on sports med, injury rehab, and diet. (Google Ross Hauser). He claims just what you were alluding to above, that individuals have individual needs in terms of diet and that some do better carb’d up, others on fats, and others on protein and claims to identify which is best for you via your response to a bolus of carbs. Seemed an interesting overlap with what you said.
Second comment- Kenyans. Some endurance coaches explain their pre-eminence as a result of their willingness to train endlessly at *very* moderate levels thus restricting the training challenge to aerobic capabilites while, by contrast, most other athletes push too hard and end up either overtrained or training in a no-mans land as far as specificity goes. In short, the claim is that the Kenyans have about a billion times more base training than the rest of the field. Have no idea if there’s any merit to that explanation.
There are a lot of reasons for Kenyan running dominance. That is probably one of them but assuredly not the only one.
Others include what appear to be clear genetic adaptations which are beneficial for running, growing up at altitude, a massive culture of running, incredible competition between Kenyan runners (which selects out the superior ones) and probably even more than that.
They also just train an absurd amounts, I’ve read reports of 3 a day training/6 days per week. A typical schedule is apparently a short morning run (fasted), a second run about 4 hours later (which ties in with research on gene experession) that is often higher quality and then a third run in the evening. They are keeping gene expression for endurance going around the clock.
Basically, they combine the right genetics with the right environment with a drive to succeed. That’s how you get champions.
My only point in bringing them up had to do with habitual diet and whether there is any merit to the idea of cyclical keto diets and endurance adaptations.
Well,
I hate to say it, but maybe the athletes perfomed like $hit cause they “felt” miserable on low carbs.
I’ve seen over and over again, once one has become fat adapted, that carbs have little impact on exercise performance. Lyle has stated himself that he has witnessed the phenominon of people working at amazingly high levels at low carbs.
I have yet to see dimished performance on 5 days of low carbs during a training cyclye, or mid season, followed by two days of higher carbs and ( pre, peri, post workout carbs around said sporting event)
Show me.
Well, some people anyhow. And my comments were generally in the context of the weight room and low-volume training. Which isn’t quite the same as endurance training or what this article is about.
Certainly not all perform well on low-carbs even with adaptation. Some continue to perform poorly. And I even addressed this within this article.
And it also depend on what we are talking about. What performance, what activity, what kind of training?
That is, Nugg, what type of event are you talking about?
As well, 2 day carb-load is the key to what you wrote.
Lyle
Im confused……then why offer the endurance variant for UD2? Are we talking two different animals?
Laura
1. The data showing impaired sprint performance came out about 8 years after I wrote UD2. I’m good, I can’t predict the future.
2. “On average, performance didn’t generally improve which led to the conclusion that the approach was still invalid. However, in the studies that showed individual data, a pattern emerged that I found interesting. The subjects who got the best performance on carb-based diets showed the biggest decrease on the fat adaptation diet. But subjects who did relatively poorer on high-carbs usually got a performance boost on the with fat adaptation.”
Endurance runner here (not elite, but “good” at the local level) and here’s my two cents:
I did VLC for ~ 9 months while recovering from a stress fracture, and eventually went back to running during that time. I was terrible. I suffered to even do two miles at a lame pace whereas before I used to rack ridiculous mileage at tempo pace. I liked VLC-ing so much though (for my figure), that I thought I would keep at it. Long story short, it took a few months of low carb running for my body to adjust to it and it did. And then, finally, upping my carbs to ~150/day (and occasionally a lot more, if I feel like a little hedonism) has put me in a sweet spot where I can run at my absolute best (ever). My racing times are in fact the best they’ve been in my life. It could be running maturity though, so who knows. One thing I have noticed, as I’ve pushed the envelope more and more carb-wise, is that over-loading (near race time) has a negative performance impact greater than insufficient carbs. I keep massive refeeds to times when no race is near, and do it for the leptin, not for any running-specific benefit.
By the way, I always run fasted. Now, before, always, my whole life, just because I felt sluggish otherwise. I can do 13 mile training runs, fasted, and in the afternoon with nothing in my tummy all day, and I kick butt while doing it. Anything but the “train low, race high” strategy is just not for me.