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Tuesday, October 9, 2018

Fasting Update - 6 Weeks In - Low Carb High Fat Experiment

Time flies when you're not... eating.

I wasn't seeing weight loss results, so I've changed a few things.

  • Longer fasting periods
  • Low carb / high fat meals to break the fast (or just before it)
Low Carb / High Fat (LCHF)

Edit: Just after I posted this - I listened to this VeloNews FastTalk Podcast.  If you have an hour, it's way better than reading "books" and "articles" or this "blog post"... I highly recommend it... he actually backs up almost everything I said below - for the recreational athlete, there's really no reason not to try a ketogenic diet... 

I'm guessing this is the most contentious.  I've also had the hardest time finding any information on athletic performance in the absence of carbs.

Finally I found two resources: this book was the first one, "The Art and Science of Low Carbohydrate Performance".

It wasn't about fasting (at all) but it did focus on using fat over carbs as fuel for endurance performance.  There are several studies and anecdotal evidence from Ultramarathon runners and such that suggest you can train your body to burn fat efficiently enough to get decent performance.

This was an exciting notion.  Best of all, I wasn't alone - there were others trying to train on empty, and even (gasp!) studies!  And folks who found real success with it.

I was chuffed.

But... I since found a study that throws some water on this notion.

The good:
...the fat-adapted athletes were able to sustain a fat-burning rate of 1.57 grams of fat per minute, which is 2.5 times greater than their “normal” values.

2.5 TIMES the fat metabolism during exercise compared to before they were "fat-adapted".  That's extremely relevant statistically, remarkable!  Considering just how much fat the average person has (enough to run/bike for weeks!) it's awesome that it's able to be tapped into to a greater degree!


...both high-carb groups improved, by an average of 190 and 124 seconds, respectively.
In the LCHF group, on the other hand, the gains in VO2max were countered by the decrease in efficiency. The result was no change in race time (they were 23 seconds slower, on average, a difference that wasn’t statistically significant)

So you start to burn more fat - which is great - but it makes you less efficient.  Ultimately, this means your top-end pace is lower, so your performance... droops.

Womp womp.


This made me think about what my goals really are.

Are they athletic performance?  Going long even if it's slow/slower?

Or just losing weight and being as healthy as I can be?

For me it's a no-brainer - I want to lose weight and be healthy.  If I can do that with a LCHF diet, I'll take being less efficient.

Also it's worth noting - VO2max comes into play when you're close to balls-out, not when you're doing an ultramarathon or a really long adventure race.  I'm doing a 24h bike race and a canoe race that'll take close to that - so being able to tap into fat for energy probably helps me a lot more than being super efficient at VO2max.

Or, per the Runners World article:
there may be a difference between Olympic-bound athletes like the ones studied here and recreational ultra-endurance athletes whose goals focus more on completing the distance than sustaining near-threshold intensities or being ready to respond to high-intensity surges from competitors. At lower intensities, the negative effects on efficiency may become irrelevant.
So I'm pretty happy continuing to keep trying to meet my endurance goals with a LCHF diet, as well as with fasting.  Everything I've tried so far has gone reasonably well - at slower paces.

Longer Fast Periods

Instead of 16:8 (16h fast, 8h feast), I've been pushing the 16 longer.  Last week my fast lengths were: 22h, 9h, 17h, 14h, 22.5h, 19.5h, 15h.  A few cheat days in there - whoops.

The biggest challenge has been pushing through lunch on work days.  If I'm at home and keep myself busy I'm fine, but at work my brain power seems to lag.

I would like to get into the 24-36h range but it's been a challenge.  Mostly it's hard to miss the family meal at the end of the day.

Weight Loss

I'm down about 3-5lbs so far.  It's hard to tell for sure, as when I'm glycogen depleted and LCHF the scale says nicer things than after I binge on carbs for an evening... but minimum 3lbs.

So I feel there's some progress, and if I stick to it............ more progress!

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