Fat adapted: Do you need carbohydrates if running on the LCHf diet?

On today’s episode of The Ask Prof Noakes Podcast we discuss how you can explain the Banting diet to people who are against it because they don’t understand it. Prof Tim Noakes puts it all into plain language for us.

Charles submitted his question for the LCHF podcast today and it has to do with explaining the Banting diet to athletes who are not following it.

Charles said he’s been asked this question by people who are against the Banting diet, and he doesn’t quite know how to answer them.

If a non-fat adapted athlete, who fuels on carbohydrate, runs out of carbs, will their body then switch to fat for fuel, or what will the body use? Likewise, for a fat adapted person, if a fat adapted person adds carbs before a race, does their body use the carbs first and then the fat stores for fuel later? And finally once those carbs are burnt out, will it burn fat first?

Professor Tim Noakes: Those are great questions and what we do know is that once you become fat adapted you metabolise carbohydrate totally differently.
So let’s start with the carbohydrate adapted athlete who’s going to run the marathon. That athlete has to take carbohydrates before and during the race, in high quantities, or else he’s going to bonk, and bonking means that the performance will go downhill, he’ll lose concentration.

Carbohydrate adaption vs Fat adaption

For years that’s the way I ran, and I became totally carbohydrate dependent, because I was insulin resistant. When I didn’t have any carbohydrates I was in real trouble. I would hit the wall big time.

I could only get around it by taking, by sucking on carbohydrates every ten minutes literally, in the Comrades Marathon.

The first Comrades Marathon I ever ran, I was a fat adapted athlete, because we hadn’t yet got bought into this high carb diet. I ran the whole way, the whole Comrades Marathon, and I think I had four drinks the whole way, and there was a minimal amount of carbohydrates.

But when I’d become carbohydrate adapted, I couldn’t do that. I couldn’t have run 30km without having all this carbohydrate.
So once you become carbohydrate dependent, you’re crippled. You’re actually metabolically crippled, because all you can do is burn carbohydrate. When you run out of carbohydrates your muscles are not really adapted properly for fat burning.

Are you metabolically crippled?

I’ve just been with Steven Finney, who was the first guy to do these studies about burning fat. He’s shown that they’ve looked at the elite ultra-marathon runners in the United States. They can cover, essentially all their requirements, when they’re running at a 2:15 marathon. In a 2:15 marathon, they can cover all their energy requirements from fat. They do not need carbohydrate.

Now these guys still do take in a little carbohydrate during the races. Most athletes who do adapt and are elite athletes, will tell you they still do a little better if they eat a little bit of carbohydrate the day before, and if they do take some carbohydrate during the race.

But instead of having 25g every half hour, it might be 25g every two hours or three hours. But it’s not zero carbohydrate. There is some carbohydrate in.

So the argument would be that the athletes need to test for themselves. If they’re only running marathons, you can get by on a marathon by being carb adapted, because you can stuff yourself with enough carbohydrate to get you through 42km.

But when it gets longer, it gets more and more difficult to supply the carbohydrates that you need, and then it makes logical sense to say, “well actually why don’t I burn the fuels that I’m designed to burn, which is fat. On top of that, I’m running a lot slower, so why don’t, I burn the fuel that is very good for when I’m running slightly slower, and that’s fat?”

Once an event or race goes more than two hour the biology is clear, you should be fatted adapted and not carbohydrated adapted. But by that, I’m not saying you have to not take any carbohydrate.

The other point I make is that carbohydrate ingested during exercise is completely safe for you if you’re fatted adapted. The small amounts of carbohydrate are not going to damage your health.
Whereas, if eating a high carbohydrate diet, both before and during, I can’t promise you that your health will be sustained in the long term, particularly if you are insulin resistant. My diabetes clearly occurred because I ate far too much carbohydrate, and I was insulin resistant, and I didn’t realise what the problem was.

Is carbohydrate adaption the healthiest alternative?

So those are some of the points I would make. There was another point I’d like to make. In our own studies of fat adapted versus carbohydrate adapted athletes, what we noticed is that fat adapted athletes do still burn quite a lot of carbohydrate during exercise, and so you say where does that carbohydrate come from?

The answer is the liver. The liver is producing carbohydrate all the time. If you’re fat adapted and not eating carbohydrate, your muscles will store that carbohydrate overnight, and so that when you get up the next day, even though you’re fat adapted, your muscles are not carbohydrate depleted. They actually do have some glycogen present.

If you’re able to store glycogen, you’ve got a liver that will produce glycogen. Now if you’re fat adapted and you take any carbohydrate, it goes straight to the muscles and is stored. You don’t burn it, you store it for later use. Whereas, if you’re carbohydrate adapted the carbohydrate you take in, you will both burn as a fuel and store in your muscles. So in a sense you wasting some of the carbohydrate because you just burn it as a fuel when you could be burning fat.

So fat adaptation has a second advantage, and that when you do eat carbohydrates you store it in the muscles. You don’t burn it as a fuel. You don’t waste it. That’s the point perhaps that people need to understand. Once you’re eating more than 200g of carbohydrate a day, a lot of that carbohydrate is just being burnt as a fuel during the day, not when you’re exercising. In other words, it’s being wasted.

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