It could be much much more than CICO. If you want to read an epic saga on modern obesity and it's theories check out

https://slimemoldtimemold.com/2021/07/07/a-chemical-hunger-p...

It seems like everything in that article reinforces CICO. Is there something that diverges from the CICO model that I might be missing?

E.G. it’s examples of the Maasai and Inuit eating higher calories make a lot of sense when you consider their exposure to temp extremes and additional cal burn coming from thermoregulation (along with probably elevated levels of daily activity).

Most of the nuance I’ve seen around CICO that holds isn’t that CICO isn’t true, it’s that the intake and output are hard to calculate when you look at nutrient absorption and lifestyle

CICO may be scientifically valid but it's useless in practical terms. People who tend to be constipated absorb much more energy from their food and those with fast digestive tracts absorb much less. Everyone is somewhere on that spectrum, so, from person to person, you would never have a practical way to assess what the CI or the CO is in the CICO model.

Au contraire, it's very useful. If you want someone to lose weight, calculate their BMR + their rough activity based cal burn, and give 'em a 15% deficit. They'll lose weight. Not just water and glycogen. They will burn fat.

If you want someone to gain weight, do the same calc, tell 'em to eat 100 more calories. Not gaining? 200. Really not gaining? Wow, fast metabolism, shock 'em with 500 extra. Anecdata, but the only time I saw someone not slowly gain on 200 extra, there ended up being a lot of walking we weren't accounting for in our maintenance cal calculation. Our O in CICO was off. For reference, 200 cals is like a 16 oz of coke, or 2-3 apples. Decently precise.

The variance between a fast and slow metabolizer isn't 20% of daily calorie burn, maybe 10% on the high end. Guesstimation, probably more like 5%. Well within the tolerances that are used for weight modulation (up or down).

If it weren't the case, why are so many body builders (natty or enhanced) able to run repeated bulking and cutting cycles? Are they genetic outliers?

Can you calculate it 100%? Nope -- so many variables, probably tons we don't even know about yet. But it's accurate enough to be very effective, and very simple to implement.

Mark Pimentel's lab which studies disorders of the gut has hypothesized that people with extremely slow transit times can absorb 2-3x the amount of energy from food in comparison to people with regular transit times. I think there is a high amount of variability; and importantly in the context of losing weight, people who are overweight often have slow intestinal transit due to their dysregulated gut microflora.

I'm sort of with you, but it sounds more to me like: start eating less, and you'll lose weight; eat more, and you'll gain weight. There's just too many variables here that change how food is metabolized and digested; including the microbiome which CICO ignores.

You got a source for that study? A cursory google didn’t reveal anything and 2-3x is suspect. To your second point, wouldn’t the microbiome (and slow digestion) just be another input into CICO?

is it just caloric absorption, or are various essential nutrients also absorbed more and less? asking because coffee can speed up my transit time dramatically, and I'm always down for cutting calories!

AFAIK this has not been studied, but I would assume that nutrient absorption could feasibly vary with motility speed just like energy absorption. For example people with chronic diarrhea are usually deficient in several B vitamins especially B12, although their poor absorption may not be only due to rapid transit time and could stem from other gut issues. Rapid transit time is certainly a factor though.

I don't count calories and I will never start counting calories. Hence it is useless.

you are ignoring what he said. I don't know if it's true, but he's saying CI is not simply a function of how much you put in your mouth, but how much of that your body absorbs.

the other answers here are more detailed, I just wanted to state it simply.

Not ignoring it - the in in calories in isn’t what you put in your mouth, it’s what you can absorb. Hence why you don’t count fiber towards your calories.

Again, the digestion point seems to reinforce CICO. If you gain weight because your digestion is slower (let’s grant the point), it’s not because your body some how treats calories differently, it’s that you’re getting more calories from your food. Your calories in are higher.

Not to mention that diet products have existed to game your digestive system to absorb less calories from your food. With the rationale being… less CI in CICO. See also: folks abusing laxatives for this purpose

I also say, to whatever readers may care, the reason I belabor this point so much is that obesity related health issues have a massive effect on QOL, public health and personal mental health. I say this having grown up in the southern US, having obese family, having my own fitness / weight loss problems, having seen gangrene diabetic foots with my own eyes. I know vividly what it looks like for someone you love to be heavy, miserable specifically because theyre heavy, and totally hopeless that “they just can’t lose the weight”.

Throwing information out like this (w/o source and at best poorly replicated), that CICO is useless because of digestion rate, is incredibly dangerous because it falsely legitimizes that hopelessness. It traps people. And it maybe only applies in <1% of cases, where you have not just obesity but also compounding, very specific digestive issues. The opposite is also true — you don’t just drink coffee to knock off enough cal absorption to make a diff — you take laxatives you don’t need and have extremely abnormal, frequent BMs.

Anyone and everyone can lose the weight. It’s just CICO. You gotta figure out your input and output to account for the minor individual variances, and lock in a lifestyle to do it. But it’s just CICO at the end of the day.

CICO is axiomatically true, but the problem is CI is easy to measure and CO isn't.

Different people use different amounts of calories to do the same things (including sitting around), and different people extract different amount of calories from the input. Some people can extract calories from PF Chang or Buca di Beppo, but not me. Weight control by eating foods that go straight through sounds terrible though.

The problem is that the body and brain operate a complex control loop whose sole purpose is to regulate calories in and calories out.

You can run an additional control loop mentally but what purpose does that serve? Reducing caloric intake while your body screams increase caloric intake is very difficult. You should instead use the control loop you already have.

>this is bro science

sorry, I don't care