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Scientist busts myths about how humans burn calories

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Re: Scientist busts myths about how humans burn calories

#581

Post by tom-thistime »

wildmanx wrote: post #572

Irony. A linked article describing a scientist trying to rigorously find out how weight changes and energy expenditure and diet are connected, revealing the little we do know and the vast sea of what we do not know. The discussion here: full of anecdotes and bro science berating one another "that's not how it works, it works like this", "I personally do this-and-that", "you just have to x-y-z, it's that simple".

Yes. And no. Bro science is more or less useless. But the article isn't super useful either. Calories burned are "adjusted for nonfat body mass." Adjusted how?

Fat stores energy. Food adds energy. Exercise uses energy. Those aren't "myths." The article (not talking about the scientist) is very difficult to understand, but it seems to come down on the "myth" side of that dilemma. Mostly. Kind of.

Re: Scientist busts myths about how humans burn calories

#582

Post by csee »

noduerme wrote: post #310
deepnotderp wrote: post #282

The conclusion is almost certainly wrong: 1. From a simple sniff test, if this were true, then athletes wouldn't need a lot of calories. This obviously isn't true, eg Phelps eats 8-11K calories a day. I personally eat around 3.5K calories a day. If exercise didn't impact caloric burn I assure you I'd be a lot fatter... 2. The only plausible mechanisms for why exercise wouldn't result in more overall caloric burn is t…

>> somehow the sedentary lifestyle of your average couch potato What I got out of the article wasn't that sitting still and not thinking can somehow burn calories; just that strenuous mental activities can burn a great deal more energy in humans than in apes. This is believable to me. I'm a person who falls asleep doing math in my head every night. I got a chance, during a year of pandemic lockdown, to experiment wit…

> strenuous mental activities can burn a great deal more energy in humans

Could be the body stress response associated with doing those activities

Re: Scientist busts myths about how humans burn calories

#583

Post by alistairSH »

tempestn wrote: post #400
Elte wrote: post #321

Earlier quoted context omitted.

I'm a bit confused by this point in the article, because it also states: > There seems to be a hard limit on how many calories our bodies can burn per day, set by how fast we can digest food and turn it into energy. He calculates that the ceiling for an 85-kilogram man would be about 4650 calories per day. Given that "regular" people clearly do not burn 4650 calories per day, and it is possible to burn 4650 calories…

Yeah, the article isn't very clear on this. ISTM the claim is not that exercise doesn't increase energy consumption at all , but just that it increases it by much less than the amount of energy expended in the exercise, because the body (partially) compensates elsewhere. Whether the degree of compensation varies based on amount of exercise I'm not sure, and I wish it had explained. I expect it probably would, as pres…

I can definitely see how that works. I'm a cyclist and often ride 60-100 miles on a weekend day, plus 3 days pf 20-30 miles during the week. That should be a lot of extra calories. But, after those long rides, I usually need a nap and don't do much else (maybe grocery shopping, but definitely not woodworking or other serious projects).

That said, at the peak of my training (12 hours/week), I can definitely consume more calories without putting on weight. Like, a giant bowl of ice cream most nights. But, if I continue that diet during recovery periods, I'll put on a few pounds. So, it's not that exercise has zero impact, but possibly quite a bit smaller an impact that one might assume.

Re: Scientist busts myths about how humans burn calories

#585

Post by alistairSH »

hgomersall wrote: post #392
Elte wrote: post #321

Earlier quoted context omitted.

I'm a bit confused by this point in the article, because it also states: > There seems to be a hard limit on how many calories our bodies can burn per day, set by how fast we can digest food and turn it into energy. He calculates that the ceiling for an 85-kilogram man would be about 4650 calories per day. Given that "regular" people clearly do not burn 4650 calories per day, and it is possible to burn 4650 calories…

Yeah, I thought this. There's clearly an amount of exercise that will cause you to lose weight. An interesting question is whether your body prevents you from achieving that. Cycling was always interesting to me in this context because it seems easier to burn energy on a bike than other forms of exercise.

seems easier to burn energy on a bike than other forms of exercise

I'm not sure this is true. Cycling isn't weight-bearing (you're sitting down) and only engages the large leg muscles. Running and rowing likely provide more calorie burn for a given RPE (rate of perceived exertion) over a fixed time period. Running because it's weight-bearing; rowing because it engages more muscle groups. That said, you can probably cycle for more hours total, if you have nothing else to do.

Re: Scientist busts myths about how humans burn calories

#586

Post by twoheadedboy »

csee wrote: post #523
Xcelerate wrote: post #487

The article seems to miss what is (at least to me) the most interesting follow-up question: if exercise doesn’t cause a person to burn significantly more Calories throughout the day to induce weight loss, then what does? I’m somewhat hard-pressed to believe the answer is diet alone. Anecdotally, when I was running 100 miles per week in college for cross country, I ate three or four giant meals per day and maintained…

The article proposes stress and inflammation.

The obvious follow up I was expecting that wasn’t in the article was “do people who exercise have less stress response to stimuli?”.

They talk about a “caloric balance sheet” so this makes sense to me.

Re: Scientist busts myths about how humans burn calories

#587

Post by magicalhippo »

csee wrote: post #423
ajuc wrote: post #410

Earlier quoted context omitted.

Well one obvious adaptation is losing fat = less energy needed to move the body.

We saw a very large reduction in caloric expenditure in people who were already very fit runners. So body weight changes over the course of the experiment are unlikely to explain it.

So if they just kept doing the experiment they would end up not needing to eat?

Clearly there are some details that matter here...

Re: Scientist busts myths about how humans burn calories

#588

Post by pawelmurias »

wildmanx wrote: post #572

Irony. A linked article describing a scientist trying to rigorously find out how weight changes and energy expenditure and diet are connected, revealing the little we do know and the vast sea of what we do not know. The discussion here: full of anecdotes and bro science berating one another "that's not how it works, it works like this", "I personally do this-and-that", "you just have to x-y-z, it's that simple".

The article itself mixes results of studies with strong opinions like:

> “You can’t exercise your way out of obesity,” says evolutionary physiologist > John Speakman of the Chinese Academy of Sciences. “It’s one of those zombie > ideas that refuses to die.”

Re: Scientist busts myths about how humans burn calories

#589

Post by verisimi »

wildmanx wrote: post #572

Irony. A linked article describing a scientist trying to rigorously find out how weight changes and energy expenditure and diet are connected, revealing the little we do know and the vast sea of what we do not know. The discussion here: full of anecdotes and bro science berating one another "that's not how it works, it works like this", "I personally do this-and-that", "you just have to x-y-z, it's that simple".

The problem is that the funders of scientific research (corporations, governments, military) see zero upside in finding simple answers. There's simply no money in 'better living'.

This sort of research is only of value in so far as it moves forward some sort of saleable treatment.

In the meantime, the more confused you are about what to eat and how to treat your body - the better. It is when people are damaged that the medical industry makes its money.

In summary, the incentives for health are in reverse (and perverse, IMO). People get paid for treating disease (and even keeping them unwell!) but not for keeping people healthy.

Re: Scientist busts myths about how humans burn calories

#590

Post by maxerickson »

scotty79 wrote: post #575
maxerickson wrote: post #557

Earlier quoted context omitted.

The CO2 concentration going up in the blood increases the efficiency of respiration (because it is ultimately diffusion). You don't necessarily need to exchange 10 times the volume of air to deal with the additional CO2.

Range given for concentration of CO2 on exhaled air is 4-5% So it looks like it could be 25% difference at most.

I doubt the 4-5% you saw is a first principle of breathing.
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