[nine_k]

It consumes fuel twice as fast? Fuel is cheap.

If there any evidence that intense mental loads somehow wear down the brain, or the body as a whole, any faster? If anything, I only know that intense mental loads stave off the onset of Alzheimer's.

[arcticbull]

Animals up to rhesus monkeys which reduce their caloric intake have reduced incidence of age-related and of all-cause mortality [1], and this is conserved - at least - in rats, mice, fish, flies, worms and yeast [2]. While the fuel itself may not be expensive, there is evidence that consuming/using it is anything but. These studies are for obvious reasons difficult to conduct in humans, though I would be very surprised if they weren't under way, and time will tell.

[1] https://www.nature.com/articles/ncomms4557

[2] http://ajcn.nutrition.org/content/78/3/361.full

[JamesBarney]

Running also increases caloric and definitely doesn't reduce lifespan in humans. So the abstraction "increase energy causes bodies to wear out faster" is very leaky, and probably so leaky that it's not super useful.

[mamon]

Depends how you count it. Humans are quite effective engines - number of calories burned per hour of running is quite low, and you only do it for limited number of hours per week.

At the same time runners tend to be the kind of people that are very concerned about their health, so they eat healthy food, with moderation.

So overall caloric intake of a runner can be much less than that of obese couch potato.

[Chris2048]

> definitely doesn't reduce lifespan in humans

Compared to what though? The average sugar-addicted citizen? Someone who does no exercise?