And yet the article you're commenting on says that you don't burn more calories by exercising...
If it is true, it definitely changes the narrative.
> 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 per day, there must be a point at which exercise _does_ increase energy expenditure. I'm guessing it just doesn't happen for regular doses of exercise (including, evidently, walking 14km per day).
Perhaps the body down regulates calorie-consuming processes to a point where it's just the bare minimum, and calorie expenditure increases from there. Or perhaps we should take the opposite view and say that our bodies up regulate unwanted processes (like inflammation) to use the energy of an engine designed to keep running at a certain level?
Either way I find this incredibly interesting. And either way I'm probably also going to keep stuffing my face on a day I run 30km :).
(i know your body starts compensating for it and burning less calories, but still)
Well, we probably need to look at the direct quote again.
> 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.
Maybe i'm reading this wrong, but if one's body were to burn calories at 100% of this supposed possible rate, then by the time you'd reach 4650, a new day would start.
If digestion would top out at 4650 calories at day, with 24 hours per day, it would come down to 193.75 calories per hour. Or, in other words, it'd be about 3.23 calories per minute.
You don't need to be at the limit of human energy intake to see what happens to people when their energy expenditure greatly exceeds the energy available from food over a sustained time period; there is quite a lot of medical literature on the effects of such... er... malnutrition.
There are loads of videos on YouTube of what happens. You may or may not want to watch them. Spoiler alert: you vomit when you eat too much.
The vomit limit is probably higher than 4560 (which BTW has a suspicious number of significant digits), there might be a range between too many calories and vomiting where your body breaks down the food into waste without digesting any more nutrients/calories. Kinda like how if you eat too much vitamin C, you’ll just pee most of it out.
Cycling was always interesting to me in this context because it 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.
Contrast this with cycling which is pretty much all concentric contractions.
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.
Of course there is. The problem is that it's much easier to eat than it is to exercise. You can eat a Big Mac in 5 minutes, and you'd have to run or bike for hours to burn those calories off. A 30 minute jog on a treadmill won't do it.
Most people eat more calories than they need, and would have to exercise much more than they realize to burn them off. So losing weight over a reasonably short period of time almost always requires cutting calories. Few people have enough free time to do it with exercise alone.
What's tricky is that in early 20s I was eating about as much and it was fine.
All else being equal, resting metabolic rate doesn't tend to slow down much as we age. The notion that people in their 20s can eat as they want without gaining weight is mostly a myth. It's more likely that you don't accurately remember what you consumed and your activity level in your early 20s.
Maybe I should bring it up with a doctor, but I feel fine, I just also spend more on food than most.
BTW there are diseases that reduce calories absorbed, you might want to get checked for colitis ulcerosa and crohn's disease. They have nasty side effects so better to know earlier even if you don't have the worst symptoms.
Also that Phelps thing is highly questionable. He says he "probably" burns 8-10k, not 12k. Not the type of statement you want to rely on to dismiss all this work.
Clearly there are some details that matter here...
I'm pretty sure this doesn't apply to extreme cases like modern athletes, who explicitly push their bodies in many ways that normal fit people don't, and who have teams of doctors and coaches that can force them to keep up with exercise and diet even when their bodies are telling them to stop.
I'm not sure how base metabolic rate relates to incidental energy expenditure. My gut feeling is that every body has its own limits on energy expenditure, and max TDEE doesn't need to correlate directly with base metabolic rate. That's why I mentioned the integral above. I tend to think of $TDEE_{max} \simeq MBR_{base} + E_{available}$ but $MBR_{base} \simeq \int_{t=-5}^0 TEE(t)$ -- and in my experience, weight loss correlates more with base metabolic rate than with caloric intake ($E_{available}$).