Low Carbs Athletic Performance

This week, I cycled a total of 120 miles with the longest ride at 47 miles.

In the past, when cycling more than 25 miles, I used to carry a snack with me - a muesli bar or scone and an apple plus water. This was for refuelling, so that I would not "hit the wall" after a couple of hours' cycling. This usually occurs after about two hours, when the body's carbohydrate reserves (glycogen) are depleted. It's most commonly seen at the end of running marathons. But suppose it was possible to use a different fuel, one that wouldn't run out? How would that affect performance?

On my long ride on Tuesday, I took a snack along, as usual, but instead of a carbs snack, I took some raw nuts and cheese because I am on a low carbs, high fat diet, but this snack remained untouched.

Earlier, I had eaten a breakfast of coffee, cream with a 100g apple and 100g of nuts - walnuts, Brazils and almonds. That was just before 9 a.m. Then I cycled for four hours and finally ate again at 3 p.m. I had only a little water halfway round. Why did I have the energy to keep going? I had virtually no glycogen reserves, but had plenty of energy and never felt unable to continue. That is because I have adapted recently, to using fat as my primary fuel.

I was cycling at a steady 70-80% HR max, (70-80% of 220-age) so there was plenty of oxygen available for fat burning.

In the morning, before breakfast, I analysed my urine and the result showed I was still in ketosis i.e. my liver is converting fat to ketones. This means in effect, I had an almost unlimited fuel supply from my fat reserves. It probably explains why I needed no food until 6 hours after my breakfast, despite burning about 2000 kcals. I may also have burned some muscle, but this would be negligible, as my protein consumption is adequate.

If you are an athlete and would like to learn more about endurance training on a High Fat diet, compared to the more typical High Carbs regime, look at this recent lecture from the American College of Nutrition which explains the science behind this;

https://www.youtube.com/watch?v=JgU8z-h3IKY

More athletes are successfully competing on low carbs diets, including Dr. Peter Attia, a cyclist and distance swimmer. See him here;
https://www.youtube.com/watch?v=hB7aGnfLB-8

Then there are these athletes (I was looking for one particular example, but found several on this page, so I haven't read them all yet). See their experiences here:

http://www.dietdoctor.com/?s=lchf+athletes&submit.x=0&submit.y=0#