Making Sense of Incremental Exercise Test Fat Oxidation Data


Fat oxidation, and fat oxidation rates get talked about a lot in the world of endurance sports and triathlon. Of course, being able to break down fats for use as fuel during prolonged exercise is an important determinant of performance in ultra-endurance events like Ironman. Our other fuel source – carbohydrates – are relatively limited and are depleted during prolonged or intense exercise. Being able to use fat effectively reduces the rate at which we burn through our carbohydrate stores, and thus delays the fatigue associated with depleted carbohydrate stores, or ‘hitting the wall’.

Given that having a robust capacity to make use of fat stores during exercise is important, I quantify it in the lab with the athletes I work with. We can measure fat oxidation rates during exercise using a technique called indirect calorimetry, which involves the collection of expired air, and we typically do this across a range of exercise intensities in...

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How do I fuel my races with low carb healthy fat? - Fat Oxidation and Race Fuelling (Part 1)

F2wwc6rmr3wzvbdz6jo9 screen shot 2019 03 05 at 3.21.53 pmIt’s Monday, and we’re fresh from some great racing at Ironman New Zealand. It was really great to be down watching some racing again (and yes, I did miss racing myself!).

While down at the event, Prof Grant Schofield and I were invited to present on the low carbohydrate healthy fat (LCHF) performance for Ironman.

The link to the presentation can be found in this closed Facebook group here (anyone can join), and we think it was quite well received with 50+ people attending.

However, as always around racing, one of the main questions we always receive is “how do I fuel my races with LCHF?”. Luckily, along with two of my endurance physiology colleagues at AUT, we discussed this very topic in a paper that used theoretical energy fuel requirements of Ironman triathletes at different performance levels (~8 h, ~9 h, and ~13 h).

This paper was published in the Journal of Sports Medicine, and I’ve tried to summarise below. The science is quite heavy...

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