[sfifs]

Actually not so much surprisingly - the key exceptions being if you are working in very cold climates where the body has to generate more heat to keep you alive or you're training competitively for very physically sports.

It turns out that about 70-80℅ of what most people consume goes into simply keeping them alive (research basal metabolic rate & daily calorific requirement) and the impact of "work you do" is only a small variation - with the above exceptions.

Also interestingly (unable to search the paper reference on phone) there is research that shows that dramatically different lifestyles like Namib desert nomadic hunter-gatherer vs. typical urban don't actually differ on metabolic rates (accounting for non-fat weight)

[thaumasiotes]

What is the claim you're making? Assume 80% of Example Man's diet is his rest energy requirement. The other 20% goes toward discretionary things like moving. This means that if Example Man doubles his discretionary activity, his food consumption will increase by 20% rather than 100%.

It does not mean that if walking three miles takes one apple worth of energy, Example Man actually only needs to consume 0.2 apples in order to walk an extra three miles. He needs to eat the full one apple. This article doesn't consider food as a percentage of your diet at all; it considers food as the cost of moving. Your point isn't relevant.

[allendoerfer]

You should have posted that at the top level, so this could be the top comment. While the statistics are nice to look at, I have read the article you mentioned, too (was on HN a while ago) and instantly thought that metabolism unfortunately renders the whole calculation useless and wrong.

[thaumasiotes]

> While the statistics are nice to look at, I have read the article you mentioned, too (was on HN a while ago) and instantly thought that metabolism unfortunately renders the whole calculation useless and wrong.

Why did you think this? Can you articulate a change that metabolism would make to the calculation?

[allendoerfer]

It adapts, like my parent comment has said. Most of our energy is spend on keeping the system running, not running with our feet. If we start to run, we burn more energy, because our metabolism has not adapted yet, once it adapts (see his example with Africa), there is very little change. Obviously this is simplified.

[thaumasiotes]

Are you claiming that running requires no more energy than sitting? If not, what are you trying to say?

The energy that you need to spend on overhead doesn't go down because you start running.

[allendoerfer]

I am claiming that there is no linear relationship between the amount of running and burned calories.

[thaumasiotes]

So what? If you propose to have someone do some amount of running that they wouldn't otherwise have done, they must pay for that running in one of two ways:

1: Eat more. This has a linear relationship to the amount of additional running.

2: Do less. By doing less, you can redirect calories that would have been burned anyway to the task of running. You cannot, by definition, redirect calories that are budgeted for the basal metabolic rate.

By paying for the extra running "in kind", by not doing activities you would otherwise have done, it is easy to show a nonlinear relationship between "total running done" and "total calories expended". But that's spurious, it has nothing to do with the energy cost of running. There is a linear relationship between "total running done" and "total calories expended on running", and that is what matters when calculating the cost of running.