This is just plain dishonest writing. Just because there are other variables, or that different people burn different amount of calories, does not make 'calorie in and calorie out' wrong. If John burns 2000 calories a day and has different organisms in his gut from Sarah who burns 1500 calories a day, in no way disproves calories in / calorie out. All it proves is that people are different, a premise that the modern science community seems to find a challenging notion.
People are indeed different and the scientist you quote is saying precisely that.
You are trying to find a loophole here that doesn't exist. If two people burn the same amount of energy E_O ("out") and take in the same amount of energy E_I ("in") with E_I < E_O, then both of them must take those calories from somewhere else in their body and must therefore undergo weight loss. There is no way around that.
Now, notably you didn't specify E_O, you only said
> the same level of physical fitness and physical activity
which can mean a lot of things.
All the supposed loopholes work in exactly the same way: It might not be entirely clear what the values of E_I and E_O are, so "calories in, calories out must be wrong". (Which, again, is impossible because it's just conservation of energy, i.e. a law of physics.)
In any case, just like you can bound E_I from above by counting calories, there are ways to constrain E_O from below: If both people have the same mass (say 100kg) and walk up the staircase in one of the towers of Cologne cathedral (~150m), then they will both have spent at least E_O >= 100kg * 150m * 10m/s² = 150,000 J.
This[1] is a good summary of a talk she gave about a year ago and in it she talks a bit about the non-CICO factors in weight gain or loss. Here's one example:
“The gut microbiota of those that are lean versus those that have obesity are quite different, so much so that we can often take the gut microbiota out of individuals that are lean and place it in those that have obesity and see weight shifts with no other modifications."
Why did I know this before I even looked?
>“The gut microbiota of those that are lean versus those that have obesity are quite different, so much so that we can often take the gut microbiota out of individuals that are lean and place it in those that have obesity and see weight shifts with no other modifications."
Yeah, so all that effects is CO (calories burned). This does not disprove CICO. I see Fatima has a limited grasp of logic.
Not necessarily. In this case I think she is referring to calories that are not absorbed but are excreted.
Meaning if you are naively doing calories in vs calories out, or doing desired estimated calories out based on a table, you have an error factor significant enough to skew your results.
What we call it doesn't matter, but what GP said is actually incorrect as written.
Please do point out which part of my comment is incorrect.
> Meaning if you are naively doing calories in vs calories out, or doing desired estimated calories out based on a table, you have an error factor significant enough to skew your results.
What does "naively doing calories in vs calories out" mean exactly? I agree that some people do it naively but where exactly was my comment naive?
> Calories In vs Calories Out is mediated by a factor, usually labeled S, which accounts for the individuals own metabolic factor.
Yes, the metabolic factor affects the numeric value of E_I and E_O (I never disputed that), but once you have determined their value (or bounded them as in my comment – which, as demonstrated, is orders of magnitude easier), the statement "weight loss occurs if E_O > E_I" remains correct.
Taken literally calories in vs out is of course true.
No, they actually dont assume that only physical exercise has an effect on calories burned. In fact, CICO is agnostic to the means by which calories are burned.
> This is why just restricting calories in and exercising more won't necessarily mean you loose weight.
Actually, so long as you burn more energy than you consume, you will lose weight. Again this is agnostic to how the energy is burned. What the body does to adjust is merely effecting the amount of energy burned. It does not effect the formula concerning CICO.
If using the system got you to eat differently, and eating different made you lose weight, then congratulations, but that doesn't prove that the food you ate was actually X calories or that you actually burned Y calories, and that that deficit is why you lost weight, nor does it mean that someone else who ate as much as you did would have their body change in that way.
The model is also an abject failure when it comes to the individual psychology of overeating. This is where people like the above doctor says it's "just wrong". CICO as the only method of weight loss is about as effective as quitting smoking cold turkey (3 to 5% success rate). In general getting people to stop eating high caloric density / high glycemic index foods and replacing them with something else is a good starting point. You're effectively lowering the CI but not requiring a cutoff point for the individual.
EDIT: i wanted to mention something someone downthread hit on and that was also in the Maintenance Phase episode. Calorie burn is not constant and your body will adjust, so for you to effectively count calories and stay below some threshold you have to track what your body is burning as it adjusts which is probably very difficult.
I can imagine the podcast took off because people are hungry (pun unintentional) for something that validates inaction on improving their bodies. That show treats any sort of ambition about one's body as an eating disorder or unrealistic goal.
oh and we (my wife and I) found the Maintenance Phase podcast by following Michael Hobbes from You're Wrong About which is another entertaining podcast. I don't always agree with his politics but if I ever met him i'd shake his hand, he does a really good job.
The only thin that makes this complicated at scale is that different people are addicted to different foods, so need to cut out different things to start losing weight. But CICO is the basis for all of those.
First, note that the calorie estimates on food packaging can be off, sometimes by as much as 25%.[1] Restaurant foods have an even wider discrepancy. [2] And as you point out, different people will digest them and absorb different nutrients from the same food making comparisons difficult. For example, I absorb a small fraction of the calories from dairy products because they unfortunately pass through my digestive system quickly and remain largely undigested.
And as others have noted, accurately estimating calorie expenditure can also be difficult without professional equipment, so in practice measurements of calories expenditure can be off by a significant margin as well.
Combining all of these sources of error can result in excessively wide error bars. Someone who relies on calorie in/out estimates to dictate their consumption may end up eating significantly more or less than is optimal.
Of course, even if counting calories in/out is wildly inaccurate it might still have a positive effect if it causes people to be more aware of the food they eat. Unfortunately I'm not aware of research that teaching people to count calories results in better health outcomes than other diet strategies. (Though it does seem to increase people's odds of developing eating disorders. [3])
It's one of those cases where the theory may be correct in theory but that doesn't make it particularly useful in practice.
[1] https://pubmed.ncbi.nlm.nih.gov/8371446/ [2] https://pubmed.ncbi.nlm.nih.gov/21771989/ [3] https://pubmed.ncbi.nlm.nih.gov/30155857/
I'm astonished how many commenters are desperately trying to find loopholes in simple laws of physics.
I (and most of the other commenters here it seems) keep trying to communicate that it is possible to be both technically correct and simultaneously not useful as a weight loss strategy.
It wont work for everyone though, since many people can't make themselves eat less without following some rituals, the problem there isn't CICO but that those people can't implement a CICO diet properly. But that doesn't mean that CICO is a useless concept for losing weight, it just means that those people needs more help to keep their psychology in check.
Saying that CICO isn't useful when CICO is the basis for every single weightless diet in existence is just ignorance or a lie. All weightless diets either makes you absorb less calories by some method, or make you burn more calories, so the first thing when looking at a diet is asking how it relates to CICO. Trying to sweep that under the rug as some old school nonsense principle that has proven to not work just proves how much nonsense there is in nutritional "science".
Knowing what mechanisms and processees go into losing weight can make the journey much more intellectually stimulating, satsifying for the participant and smooth out incredibly rough bumps in the road to losing weight. CICO can't fill this need for tailoring weight loss to smooth out the efficiency losses you get with brutal cuts into one's life and psyche.
Pumping out a single metric and hammering flat all the differences in personal process with psychology and ritual screams of unnecessary suffering. It's probably wrong to use oneself like that.
Very few people live according to the physics based description of what their life should be... However one would derive that idea without hiding or ignoring personal presuppositions?
If you're simply referring to the physics of CICO that underpin most diets then I have already acknowledged it is correct.
But being correct does not make it necessary knowledge for people looking to lose weight any more than Hamiltonian mechanics is necessary knowledge to play tennis.
If I still haven't managed to convey the distinction between technical correctness and practical utility yet then I have to conclude this is a gap I cannot bridge and I wish you luck.
Every single piece of advice listed can and should be done in addition to counting calories.
The single best heuristic we have for weight loss continues to be “calories in - calories out” simply because you cannot escape thermodynamics.
Yes, your base metabolic rate may be different than others and may change over time. Yes different foods are processed differently by your body. This changes the variables, but again, does not change the calorie arithmetic.