My Long Slow Fat Adaption

When you listen to guys like Dr. Timothy Noakes, they talk about the notion of being "fat adapted".

The idea is if you restrict carbs, your body starts to use fat as its primary fuel.  This is backed up in studies - at the end of carb-restricted training periods, the fad adapted athletes burn 2.5 times as much fat for fuel, and they do this from the very start of their activity.

Here are my experiment runs...

Run 1.  20km, 6:30/km.  Bonked bad.  3 weeks into IF.

Run 2.  21.1km  6:09/km.  Better.  Almost 2 months of IF, 2 weeks of HFLC (sporadic).

Run 3.  21.1km  5:52/km.  Much better.  Almost 3 months of IF, using HFLC more regularly.  Felt strong and comfortable.

The really interesting thing about Run 3 is that I was actually 16h fasted and consumed zero calories during the run.  I had nothing but black coffee and water for 16 hours, plus another 2 hours of running.

In fact, I had biked the day before for 1.5h (water only), and had eaten HFLC the rest of the day.  So I hadn't had any kind of significant carb for almost 2 days, and had even burnt off some of what I would have had stored on that bike ride.

I find this all remarkable. It's exactly what Noakes predicts, but it still goes against so much orthodoxy.  I was kind of sure it would fail.  I'm shocked.

Questions still remain. 

Am I able to perform better than I did as a high carb athlete?  Sure I can get through a 21.1km long slow run, but can I push the pace?

Can I actually go longer?  How much longer?

Is the weight loss permanent?  (I'm down about 10lbs so far, give or take).  Or like most calorie restricted diets, will it come back, and bring friends?

I also still have some questions about "high fat, low carb" vs fasting - the athletes seem to be doing HFLC and I can't find much about fasted athletes.  I'm guessing it's because they're generally not overweight to start with, so fasting doesn't really enter the equation.  My main question: does it matter during activities if the fat I'm burning is coming from my (ample) stores rather than from food I just ate??  I'm still trying to find the answer to that.

From Experiment to Lifestyle Change

I'm making this permanent.  Even if my performance were to suffer (and I'm not sure yet if that's the case, but if) I am meeting my real goals.  I'm losing weight.  I feel great.  My mood is great, even.  I'm able to do the activities I love. 

To the moon, Alice!

Performing Fasted: The Debate Around Fat and Performance

There's a wild debate in the fitness community between the High-Fat-Low-Carb (HFLC/Ketogenic) folks and the traditional High-Carb-Low-Fat folks.

(Protein just kicks around in the middle - let's park him for now)

Tradition says: eat carbs, a lot of them, they're your most effective source of fuel.

HFLC says: you can do just as well (better?) using fat as a primary fuel.

Who is right?

It's really difficult to discern.  

Dr Timothy Noakes

Most recently I listened to the Velonews Podcast "Inside Ketogenic and High Fat Diets".

Click here to listen.

They interviewed Dr. Timothy Noakes - who wrote "The Lore of Running" which praised carbs... only to in recent years do a 180 degree turn and support a HFLC/Keto regimen.  It is a fascinating listen.

Fat: More Energy, More Stored

One undisputable fact is that you have tens of thousands of calories of fat available to you on your body, vs only a couple thousand tops of carbohydrates.  So fat has to play some role when you get into longer endurance sports.

Studies have shown that fat-adapted athletes (those who have been on low carbs for 6-8 weeks, generally) can metabolize 2.5 times more fat per hour.  I did some quick math and it comes out to 600kCal based on some studies.  That's a very big chunk of what I need, just from the fat I already have too much for.

Performance ... Wither Efficiency?

This is where the crux of the debate is.  The good thing about carbs - they are stored in your muscles and are ready to go.  Even when you ingest glucose - it goes straight to the blood stream, it's metabolized easily and quickly.

So can fat, which has a longer metabolic pathway from need to burn, compete?

Some studies have suggested "No".  This article does a pretty good job looking at one of the studies - during a training camp, athletes who switched to a HFLC diet failed to gain any performance, vs the regular carb athletes.

Hold on, says Dr Noakes.  Those athletes weren't already fat adapted, so they were going through the adaptation while taking on hard training - maybe the results would have been different if they were already fat adapted!

It's hard to tease out for sure.  If I were an Olympian with lofty performance goals I would stick to tradition until the science is clearer.  Noakes works with those folks, though, so maybe not!

Jono's Efficiency

I have been doing intermittent fasting for about 11 weeks now, which isn't exactly the same as HFLC but at the same time it kind of is.  Low carbs, relying on fat.  When I do eat I have been lowering carbs, although not religiously.

What have I noticed during fasted runs/rides?  

Higher heart rate for sure - about 10bpm higher for equivalent running pace, poking up into the 180bpm range often with 175bpm average.  For me that's crazy territory, 180bpm is close to "sprinting to the finish".

Noakes dismisses this - sure you need more oxygen to burn fat, so what?  

My results somewhat back this up - my heart rate was high enough that I should have been completely wiped after 5km, but I did 12km with hills... so could be that my heart needs to beat faster, but am I necessarily less efficient?  Will I run out of energy and be done?

I'm going to keep chugging and monitoring it.  My goals aren't the same as an Olympian, I want to lose weight (and I'm down a whoooole bunch!) and be healthy, performance is really secondary, so I can afford to take a risk on performance.