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Comment by learc83 | Hacker News Reader

How do his results line up real world data like soldiers needing about 5k calories a day when active. Or athletes like Michael Phelps consuming 8k-10k calories a day while training?

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From my read of the article the data is heavily biased towards running as the exercise of choice, probably because measuring CO2 is easy and non-intrusive to do on a treadmill. They do mention utilizing doubly labeled water but don't say if they only used that for sedentary participants or measured a wider range of exercises.

Given I have always heard/read how efficient humans are at running if they didn't account for the differing exercise methods the conclusion being offered in this article may be flawed.

Running isn't efficient at high speeds. The same with cycling. It's funny to see people buy a bike for exercise and then roll along at a crawl, expending less energy than walking.

Cycling is roughly 5x more efficient than running/walking for similar effort. Thinking you will lose much weight by cycling is generally mistaken, unless you plan to cycle very long distances or are extremely obese already and do very little existing exercise (and this is discounting most of what TFA is saying too).

wouldn't efficiency correlate to effort? pretty sure the "effort" is the feeling of burning calories. If an elite athlete can run for an hour and burn 2000 calories in that time, they will beat a less elite athlete who can run for 1900 calories in an hour, all else equal. Put them on bicycles or a rower and they'll be able to burn the exact same number of calories (assuming sufficient training in the target exercise medium) because the limiting factor is their body's ability to process oxygen, not the exact form factor of the exercise.

I'm not sure it makes sense to look at it that way either. What if it takes you 100 calories to move 100 meters but your competitor only takes 80 calories to move 100 meters?

Running isn’t much less efficient at higher speeds. It’s harder because the calorie burn per unit time is higher, but the calorie burn per unit distance doesn’t vary that much.

It's more exercise than driving a car though, which is why I think people do that.

You're right, cycle commuting falls in a great niche. It's still fast enough to cover decent distances in a reasonable amount of time, you can still carry your grocery shopping, and it's healthier than driving while still achieving most of the same things.

That's a good point. Humans are natural runners and hikers and it stands to reason that it is very efficient compared to saw something like working in a warehouse all day moving around heaving inventory or back in the old days when people would burn thousands of extra calories a day with say being a lumberjack or coal miner.

I can't line up my real world experience with this article, I have to suspect that he may be right for his specific study parameters but that may not actually be applicable to generalized advice as it's being interpreted here.

Those are anecdotes and I have one of my own that really has me questioning this;

I’ve lost 85 lbs since the beginning of May. I lost 40/85 just since the beginning of December through today.

When I exercise I clearly lose weight more quickly. Since December I’ve been running like crazy, at least 5-10km 5-6 days/week. When I lift weights I drop pounds even faster.

Edit: Makes me wonder, though, — if I walk in the morning and solve puzzles on leetcode, would I burn more calories? When I run at night if I solve random math problems in my head will I burn more calories?

The obvious answer is that even if the body does become more efficient and reduce calories burned on other things, there's an upper limit to that. The Hazda walk 14 km per day, which is only 800 calories per day. By professional athlete standards, that's a relaxing offseason level of exercise. It's plausible that your body could cut its base calorie consumption from 2000 to 1200 and stay at a stable weight while only consuming 2000 calories, but it certainly can't cut it to -500 calories and stay at a stable weight while burning 2500 a day exercising and only eating 2000.

I didn't read the article, but it may be relevant that (IIRC) swimmers lose a lot of these calories just to maintaining body temperature while in water for a significant fraction of each day (any activity that involves spending a lot of time in water may just be quantitatively abnormal?)

I think something is being lost in the reporting. The article itself mentions 2400 kcal for a 75kg woman, and then a paragraph later talks about Race across the USA runners burning 5000+ kcal.

I think the key is in this sentence: " According to Herman, humans who are more active don’t have that much higher TEE as you’d predict". ie, you have a higher Total Energy Expenditure, but it's by less than you would calculate from just adding the energy expenditure of the added exercise.

The thing is the human body is amazing at knowing how much food it needs and will persuade you over the long haul to eat enough food to balance out the extra caloric usage whether you like it or not. His point is that eating healthy is important and watching it is more important than exercise (by far)

The article mentions that but dismisses it with some hokey assertion that professional cyclists used to mainline their calories... does not touch on how elite athletes in other sports or decades get by.

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