Max fat metabolised

(Tim ) #1

Following another thread I noticed the 31kcal per lbs of fat is the max that can be released in a day stat.

Assuming 10% body fat at 140lbs that is, 430ish calories a day.

So how does this explain an ultra marathoner doing a hundred mile race on 100kcals an hour of additional nutrition. Most of the top runners probably have close to these stats. If they were fast 100miles, 15 hours, even at 600kcal an hour that’s 7500 kcal to come from somewhere in a day?!

Am I interpreting wrongly?

Edit, I may have been being dense, assume this is over a period of time rather than a single day!

(Nathan) #2

I’m not sure about normal people, but Jeff Volek’s research showed fat-adapted endurance runners could burn 1.1-1.6g/minute of fat (https://www.sciencedirect.com/science/article/pii/S0026049515003340). I’d assume someone with a lower VO2 Max would burn (proportionally?) less during exercise, perhaps 0.5-1.1g/minute?

I know that my 24h fat oxidation is ~115g/day resting (~1000kcal/day) – you can have this measured in a metabolic chamber.

#3

@T1mbro Is that the one that’s based on the Minnesota starvation experiment? I’ve never really understood why that’s quoted so often on this forum. The experiment was high carb and calorie restriction, so a completely different insulin scenario than keto or full fasting. Those poor guys had very little access to their fat stores, but it was because they were in a metabolic bind (and had the miserable physical and psychological side effects to prove it!).

I’ve done Bikram classes and HIIT on the 3rd day of a water fast, and according to the formula there’s just no way I could have done that, which is what made me look more closely at that calculator.

There’s probably some limit for each person, maybe depending on mitochondrial health and metabolic status (and a million other variables) but generally speaking I don’t think that calculation has much to offer a fat-burner.

(Tim ) #4

That was my thoughts also but as you say it gets quoted a lot!