Can I run as fast on fat as on carbs?

I was watching the diamond league athletics on the telly last night and wondering, could I still run 400 meters in under a minute? When I was a boy I had a PB of 55 seconds. And 4 years ago pre-LCHF I clocked 62 seconds after an ill-advised bet with with my son; could I still get anywhere close to that?

The stock answer to the question "Can I run as fast on fat as on carbs" tends to be that the fastest runners are all fuelled primarily by glycogen, not fat. This may be true, particularly as they all tend to be young and insulin-sensitive; they are suited to running fast on carbs. Most of us are neither of these.

But where is the line between carb-speed and fat-speed? According to Tim Noakes this line is probably only a few minutes back from the leaders of a Marathon, or a few seconds for a 10K.

And so the number of people for who the stock answer applies is actually tiny. Look at the details of elite low-carb runners and you will see that they run sub-2:30 marathons and 30 minute 10ks. How many people do you know who can do that?

What I hope I have proved on this blog is that for everybody else it is possible to train ourselves to run just as fat on fat as we could on carbs. See this post for lots more detail on how we can train our bodies to run fast on fat.

Perhaps there is a competitive advantage to the shorter, faster races from burning carbs, but again, how many people does this apply to? Unless you are a track running member of an athletics club or still at school then it is very unlikely that you will ever run a fast 400 meter or mile race again (I'd put the parents race on sports day in a separate category here!). In which case this advantage is of no consequence, you could run just as fast on fat as you could on carbs.

And so the big question should really be, why would I want to run on fat?

Well my answer to this question comes in two parts:

• As a runner I am much happier and feel more consistently energised when burning fat. I also don't have to carry anything on long runs which is rather nice.
• As a human I am convinced that the older I get the more suseptible I will become to insulin resistance and the risk of obesity or diabetes is just too great.

And as for the standing quarter in under a minute. I am confident that I'll do this down at the track one evening this autumn.

Eating to Run

Last month the Food Programme on Radio 4 ran a 2-part series entitled Eating to Run. Naturally I was intrigued and listened in. The program covered a wide range of topics with a focus on how the food we eat can impact on our performance. 

• They spoke to expert sports nutritionists at Loughborough University about the right balance of macros and foods for elite British athletes.
• They spoke to Brendan Foster about what he ate when he was breaking world records. Toast and honey.
• They looked at what the world’s best marathon runners form Kenya eat (mostly rice and potatoes), and the diets of the running mad Japanese who eat a lot of fermented foods and run a lot faster than we do.
• They spoke to Scott Durek, perhaps the worlds most gifted ultra-distance runner. He advocates a vegan diet with lots of fermented foods as this improved the efficiency of the gut.
• And they briefly described Tim Noakes and the LCHF diet. Noakes was the great pionner of nutritional research for performance running and he now admits to have got it all wrong.

Lots of people advocating hugely different diets. And loads of contrasts; the scientists from Loughborough insist that you need to burn carbs and you need to recover quickly with a protein and carb drink; and the Kenyans (who happen to be rather better than the British) who eat nothing at all after a long training run. Brendan foster replenished his body with a couple of pints of shandy!

And the conclusions that I come to are these:

Eat whatever works for you and your body, but make sure you are not harming actually yourself.

I believe that a lifetime of high carbohydrate food is likely to contribute to bad health, especially if you are intolerant to carbs as many people undoubtedly are.

I also believe that most of the science described by sport nutritionists and quoted by Lucozade is aimed solely at elite athletes.  And as Charlie Spedding puts it so well in his biography entitled Last to First: "Why is it that most of that fastest British marathon runners in the last 40 years were running over 20 years ago?"  (In 1984, for instance, 2hr 15min was broken 25 times by British athletes. In 2012 it happened on just three occasions).  Something is not right here.

The notion that we must run on carbs in order to be champions relates to a tiny fraction of runners; and except for sprinters the rest of us could certainly run just as well on fat if we chose to and would be best off considering what energy source is more healthy. And the answer to this would appear to be to “Eat Real Food, mostly vegetables and not too much”.