Dr. Volek’s Latest Research Paper – Metabolic characteristics of keto-adapted ultra-endurance runners


I was first turned on to this latest study by Dr. Volek after listening to one of Ben Greenfield’s podcasts where he talked about his participation in a groundbreaking study that required him to run 3 hrs straight on a treadmill while undergoing intermittent blood tests, metabolic tests, and muscle biopsies!

It sounded like an experimenters dream to me in terms of the data that could be collected (although it probably wasn’t that fun for those being experimented on).

The paper was finally published a few weeks ago in Metabolism.

Here’s the link to the paper

And because sometimes these journals change the link addresses and I get left with a bunch of broken links, I’ve downloaded the free PDF and uploaded it to my site.

Here’s the link to the pdf of the article stored on my site, with my highlights.

Before diving further into the paper, I just wanted to express how excited I was to actually read it.  In December 2012, when I first started this blog to document my experiment with Nutritional Ketosis, my main sources of information were Volek and Phinney’s:

This was before folks like Lebron James and  Kim Kardashian went ketogenic, and low carb hit the mainstream.

Now, there are boat loads of books on this subject, including Jimmy Moore’s Keto Clarity, but back then, Volek and Phinney’s work was the best stuff out there.

It’s with this appreciation that I opened this PDF like a kid on Christmas day since this was their latest work, hot off the presses.

They appropriately called this the Fat Adapted Substrate use in Trained Elite Runners study, with  the acronym, FASTER (conveniently ignoring the words ‘use’ and ‘in,’ I always chuckle a little when researchers do this).

What They Set Out To Accomplish

Determine the metabolic adaptations between high carb and low carb fueled endurance athletes.

This is the first study examining these changes in athletes who’ve been on these dietary regimens for longer than a few months.

The range athletes followed these diets were 9 – 36 months, with an average of 20 months, which eliminates the potential confounding factor of inadequate ketoadaptation, which affects most current low carb studies which span anywhere from 2-6 weeks.

Exercise Protocol


Day 1

Four hour fast followed by VO2 Max test (this is what my own VO2 Max Test looked like)

Day 2

  • 10 hour overnight fat
  • Urine test
  • Resting Metabolic Rate Test (I did one of these too!)
  • Blood Sample
  • Muscle biopsy
  • Preworkout Shake
    • Low Carb Group – Heavy cream, olive oil, whey protein, walnut oil, and strawberries (seems pretty disgusting if you ask me… can’t imagine drinking a shake with olive oil!)
    • High Carb Group – Heavy cream, olive oil, whey protein, walnut oil, strawberries, banana, and agave syrup (probably tasted a little better with the banana and agave)
  • Digest for 90 minutes
  • Another blood sample
  • Run at 64% VO2 Max for 180 minutes total
    • Blood samples at 60 and 120 minutes
  • After run, another muscle biopsy
  • Post workout shake
  • Last muscle biopsy 120 minutes after run

If you want to see some pictures from the study itself, here are two blog entries written by endurance athlete Zach Bitter where he writes about his experience and shares some pictures

As you can see, this was a pretty comprehensive and invasive experiment!  Here’s how they described the muscle biopsy:

A small incision (~1 cm) was made through the skin and muscle fascia and a 5 mm diameter sterile biopsy needle… was introduced into the muscle to a depth of 2 cm.

… To ensure adequate sample sizes a double-chop method combined with suction was used.

…  The incision was then closed with a single suture. In order to avoid possible impairment of glycogen synthesis resulting from microtrauma in the area near the biopsy, we performed the immediate post-exercise biopsy on the opposite leg, and the 2 hr post-exercise biopsy 3 cm apart from the first incision site.

Sounds like fun doesn’t it?

[Here’s a picture of the biopsy being performed on Zach Bitter.  WARNING – there’s a small droplet of blood, just in case you’re squeemish and aren’t sure you want to click on it]

I had a skin biopsy from my hand a few years back (turned out to be nothing), but I remember it being extremely painful, and I was whining all day to the BJJ Cavewife about how much simple things like writing, typing, and picking my nose hurt.  I can’t even imagine having my skin incised and chunks of my muscle chopped out before, during, and after a workout!

Kudos to these research subjects for sacrificing in the name of science!

What Did They Find?

The most notable findings were that compared to HC athletes, the LC keto-adapted runners showed:

1) two-fold higher rates of peak fat oxidation during graded exercise,

2) greater capacity to oxidize fat at higher exercise intensities,

3) two-fold higher rates of fat oxidation during sustained submaximal running, and

4) no differences in pre- exercise muscle glycogen concentrations, the rate of glycogen utilization during exercise, and the rate of glycogen synthesis during recovery.

[I edited the format a bit]

This study effectively shows that long term ketogenic ultra endurance athletes burn more fat and become more efficient at using glycogen compared to long term high carb ultra endurance athletes.

Glycerol As A Marker For Lipolysis

This line in the Discussion section caught my attention:

Serum glycerol is a better indicator of adipose tissue lipolysis compared to fatty acids since adipose tissue and skeletal muscles have lower glycerol kinase activity and thus are not able to use glycerol as effectively.

I wondered if there was an easy way to measure serum glycerol.  The premise of measuring blood ketones, breath ketones, and urine ketones is to detect how much fat the body is burning.  The problem is that we can’t tell if the fat is coming from the burning of dietary fat vs body fat.

According to this, glycerol is a good marker for the burning of body fat.  Looks like Amazon has something for this… but it’s currently unavailable and the price isn’t listed.

Briefly peeking on the company website, it looks like the whole setup would cost something in the range of $5000, which is prohibitively expensive for the typical n=1 self experimenter.

*Image found here

4 Responses to Dr. Volek’s Latest Research Paper – Metabolic characteristics of keto-adapted ultra-endurance runners

  1. Ash Simmonds says:

    Some refs here that I’m yet to go through which may indicate sources and fates of fatty acid metabolism:


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