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So a probably safe comparison is Ironmans or Ultramarathons (100 milers go for 17-18 hours for the top finishers). Usually you have to put in a huge amount of c

So a probably safe comparison is Ironmans or Ultramarathons (100 milers go for 17-18 hours for the top finishers). Usually you have to put in a huge amount of carbs per hour (50-80g/hr) and a high amount of calories (250-400 cal/hr). Hydration is obviously also very important and getting sodium will be key (1000mg/hr). Outside of that you can generally limit your body's usage of fat stores though at this length and time it is probably inevitable. I would suspect that if properly hydrated and consuming calories (no easy feat after 12 hours because the stomach does really go to shit) maybe 600 net calories an hour (-1000/hr + 400/hr from nutrition) = 4-10 lbs (@3000 cal/lb). Range provided because I suspect my calculations are a little off and I'm underestimating the calories burned and probably overestimating the ability to consume that many calories/hour. TLDR: Probably 10 lbs if they are properly hydrated and fed (which this appears to be a VERY well supported achievement)

typon 4y ago
I wonder if losing weight over the course of the run itself means that it got easier for him to move near the end (of course offset by the tiredness/fatigue) - I wonder if the effect did slightly cancel out?
- darkwizard42 4y ago
  I wouldn't think it would be helpful to lose weight, the issue really is that turning fat stores into calories is quite slow (for how many calories he is consuming) and it can't be relied on as a source of energy so you just end up more tired I think. You need some amount of weight for muscle to push your body forward and I don't know that there is a big aerodynamic or energy advantage to sacrificing weight for that.
Accacin 4y ago
It's very hard to comsume 600 calories an hour whilst long distance running. A good thing to aim for is 200 calories as that's probably about the max your body can digest whilst running. However, this guy is clearly superhuman so who knows :D
- darkwizard42 4y ago
  I had the estimate at 400 calories in my post (which is on the high end for sure), which is what I know some Ultraman and ultramarathoners aim for in at least the first half or bike legs of their race. I believe 200 is enough for amateur runners, but I know professionals really load up since the calories from carbs are definitely more efficiently utilized than fat stores.

typon 4y ago

I wonder if losing weight over the course of the run itself means that it got easier for him to move near the end (of course offset by the tiredness/fatigue) - I wonder if the effect did slightly cancel out?

darkwizard42 4y ago
I wouldn't think it would be helpful to lose weight, the issue really is that turning fat stores into calories is quite slow (for how many calories he is consuming) and it can't be relied on as a source of energy so you just end up more tired I think. You need some amount of weight for muscle to push your body forward and I don't know that there is a big aerodynamic or energy advantage to sacrificing weight for that.

Accacin 4y ago

It's very hard to comsume 600 calories an hour whilst long distance running. A good thing to aim for is 200 calories as that's probably about the max your body can digest whilst running. However, this guy is clearly superhuman so who knows :D

darkwizard42 4y ago
I had the estimate at 400 calories in my post (which is on the high end for sure), which is what I know some Ultraman and ultramarathoners aim for in at least the first half or bike legs of their race. I believe 200 is enough for amateur runners, but I know professionals really load up since the calories from carbs are definitely more efficiently utilized than fat stores.