Muscle burns more energy than fat. As people age, their muscle mass declines without sufficient exercise, so we'd naturally expect the average person's metabolism to decline via this even if "metabolism per kg muscle" didn't change.
Therefore all their data is based only on fat-free mass, i.e. total body mass minus fat mass.
So all their conclusions are not influenced by the amount of fat vs. muscle.
So we could easily expect the average person's metabolism to increase as well, simply to support the extra body mass regardless of composition.
Balancing out the two effects can only really be determined through careful statistics, and is going to be extremely variable per-person.
https://examine.com/articles/does-metabolism-vary-between-tw...
All things being even 200kcal difference per day is about 20lbs per year attributed purely to metabolic difference. Now you can say to just eat 200kcal less per day, but those little differences on a daily basis add up.
As you gain weight, you burn more energy, even just being idle, so 200kcal doesn't means 20lbs per year (obviously so, as otherwise you'd gain 600lbs in 30 years).
An extra 200kcals per day implies gaining extra weight until the extra energy you burn cancels it out, and then stabilizing there. IIRC the rule of thumb is ~25kcal/day/kg so you'd just naturally balance out to being 8kg heavier than the baseline.
Only if you gain mostly muscle. Which I'd bet most people at a calorie surplus aren't, and the extra fat is burning very little calories.
In the case of two small women who burnt <=2100 a day, a 300kcal difference would be the difference between one of them fasting for an entire day every single week and the other not.
That seems like a massive difference not "small".
https://www.brainfacts.org/brain-anatomy-and-function/anatom...
Does this change over time also?
It never ceases to amaze me that we think that we know better, and yet the human body, as with other animals etc, have been around for quite some time now. Even if we had all the data from the past that we think is important now, we still wouldn't know better.
There was a post the other day regarding "The prosecutors fallacy" that might fit well with this sort of subject matter.
Estimates vary but 50 lbs of lean muscle mass is generally considered the natural maximum for men.
I increased my calorific needs by 1000 a day by doing a 10K run (1hr) before breakfast.
Still a 160lb weakling :)
The amount of extra food I needed to start eating!
I’m ~75kg. Schwarzenegger was ~120kg in his prime. 45kg difference is (2.2lbs to the kg) 100lbs (differences between UK and USA imperial notwithstanding).
The chances of me going from where I am to a AS physique is zero!
Fidgeting is a non conscious act performed throughout the day, it is not exercise. Exercise can actually reduce fidgeting and this shows up in athletes lower BMR that needs to be taken into account for meal programmes.
It is easy to eat more calories than are used in taking 10.000 steps.
And on the negative side, non-fidgety people might be more depressed or anxious mentally, more physically drained or fatigued or lethargic physically, may have had upbringings where movement drew negative attention from adults telling them to sit still, may have social upbringings where fidgeting was seen as 'acting out', may have been part a band or group where being still was trained into them, may find their own movements distracting or annoying...
No idea how accurate it is, but an extra 350 calories burned is a pretty big improvement over _not_ having those burned.
I doubt fidgeting alone is sufficient to keep most people skinny. There’s a lot that impacts our weight. But if somebody’s automatically burning calories because they have a hard time stopping fidgeting, that might ease the load a bit so they could eat a bit more or walk a little less than would be the case without it.
EDIT: it feels worth mentioning that fidgeting can be an all day activity for some people, 8+ hours. Walking 10k steps takes maybe 1.5 hours, more or less depending on the persons speed. It wouldn’t be as much of a workout replacement as a whole lifestyle change.
Often those who fidget a lot will fidget less on days where they have used significant energy intentionally. Or will fidget less if they are restricting calories.
It would be hard to purposefully fidget a significant amount, but I suppose it could be trained with the right monitoring and stimulus. It would probably be better to train some other behavior though.
The rest is likely to be due to slower rates of protein synthesis for the renewal of various body parts.
My ex-gf was one of these people and would routinely tell people about how she could eat anything and not gain weight. But when I would go on a severely calorie-restricted diet I was still eating more than she did on a normal day. I don’t think she was lying about being able to eat anything, I think she just didn’t realize how little she actually ate.
I know people (mainly Asian guys that are trying to build muscle) that seriously struggle to eat at a calorie surplus. So maybe it's not "metabolism" (which there are significant differences between humans) but also differing levels of hunger.
My little brother is about 50lbs lighter than me at the same height and we have very different builds and all his attempts to bulk fail for the same reason: no appetite. Meanwhile I’m overshooting my bulks and have to cut harder because I love eating too much.
[0] https://nymag.com/news/features/23169/
Michael’s regimen of 1,913 calories a day is exactly that: 1,913 calories every single day, 30 percent of them derived from fat, 30 percent from protein, and 40 percent from carbohydrates. Cooking for him is the same elaborate exercise in dietary Sudoku it is for all CR die-hards, only more so.
This is more impressive than even Terrance Tao in terms of outliers...nuts. Unless you tried to lose weight of study this stuff, this is no small feat. Pro bodybuilders have to eat less than 1200/day to get super-lean and this is with tons of muscle helping. This guy does it at 1900. If there were a Tiger Woods of metabolism, this guy would be it if Tiger Woods could play better golf.
Maybe metabolism doesn't change, but my ability to convert what I put into my mouth into weight gain has definitely changed for me. As a young man, I used to eat way much more and poop way much more. It was like the food was just passing through, without really getting in my body. No matter how much i ate Just came right out
It would seem like it is intentional, going by the article. They are trying to lose weight to maximize lifespan.
This is 3 miles/day. not that much. Minnesota starvation experiment subjects had to walk 22 miles/week.
Those Minnesota starvation study guys you're referencing had to use an extreme deficit to get down to concentration camp weights like that over the course of a year. It doesn't say in there, but that article with Michael Rea was written in 2006, and finding other stuff on him, he seemed to have been doing calorie restriction since at least 1999. A small calorie deficit can add up when you keep at it for a very long time. Even if his TDEE was 2200 or so, that would drop 30 pounds or so in a year eating 1900.
For whatever it's worth, I've been that size, and it was not on purpose. I grew very quickly in middle school and was extremely active. By 8th grade, I was 6'2" 120 lbs and it took many years before I got much bigger than that, and I used to buy entire boxes of donuts, Little Debbie snacks, and family-size bags of potato chips on the way home from school and eat them in addition to the pizza and cheeseburgers they served at the school. And when I got a car and started driving all my friends home, we'd usually go by McDonald's every day, and in addition to just the actual food, I'd get a McFlurry, pretty much every single day.
But unlike everyone else who seems to be wondering how that was possible and what happened when they were skinny in youth, it's not a mystery to me at all. I sometimes played basketball for 18 hours in a day. When I was driving my friends home, that was usually after cross-country practice, running for up to three hours after school. I walked or rode my bike everywhere. I almost never sat down. I rarely even slept. I could eat basically anything because it may as well have been the Michael Phelps Olympics diet. I was insanely active and using a ton of energy every day.
And yeah, when life normalized in my mid-20s, I too gained a bit for a short while, then I adjusted and ate less, and now I'm very lean again, but also bigger because I started lifting and learned to eat on purpose, in an intentional, measured way calibrated to actually meet my energy needs, not just ad hoc having whatever I crave at any given minute and not thinking about it. I understand why people don't want to do this. Even though I'm not restricting like him, at least not permanently, my diet habits are basically like Michael Rea's. I weigh everything, prepare all my own food, and eat pretty much exactly the same thing every day. It probably sounds like a slog and people want to just free graze and wonder why we can't live like humans must have lived for most of the past 300,000 years, when diets and hunger levels seemed to calibrate to energy needs automatically, nobody thought about it, yet almost nobody was fat except a tiny number of super rich idle nobility. But that isn't the environment we live in any more. People are extremely sedentary and randomly selected food from anywhere is utter trash loaded with extra calories in every possible form for no good reason. Unless you have the activity level of a middle schooler from the 90s or an Olympian, you need to actually try.
In every case I guarantee they eat a normal amount of calories but feel like they eat a lot because they eat slightly more calories than normal in a single meal.
Like me eating two entrees at dinner at 16 and wowing everyone even though I skipped breakfast before school to play Runescape and had a tiny school lunch.
Multiply the lb/week you were supposed to gain by 450. Your TDEE calculation was incorrect by that amount.
Their mitochondria use UCP1 [1][2] to generate more heat when producing ATP, thus wasting energy that would otherwise be converted to fat.
So to answer you question, hormones