Great hoppin’ horny-toads; CICO getting the bad rap once again… 
It’s not supposed to. CICO says, “This is what’s happening.” It’s up to people to figure out the “whys” if they are in doubt, or what to do about it if things are not going as desired. Is it so bad to have this absolutely correct thing that doesn’t provide additional insight, and doesn’t claim to? CICO is just an accounting, it’s just a scientific observation, like the odometer on a vehicle.
Scientific observations need not provide “all the answers.” A vehicle’s odometer says the vehicle went 100 kilometers. It doesn’t tell us the reason for the trip, nor who was driving, nor what the previous owner’s preference in hot peppers were. That doesn’t mean the odometer is “useless.”
Some others criticize CICO not because of the above, but because they assert that by looking at only one part of it, certain necessarily correct conclusions should then be able to be made. This is naturally not the case, and they then claim that because of it, CICO is invalid. This is a strawman argument, because (obviously) both calories in and calories out must be considered.
If you want more explanation and insight, things need to get more conditional. For example, we can say that higher insulin levels can result in matter being stored rather than metabolized, making for weight gain. Likewise, we can make CICO conditional too, dealing with predictions of what can occur, CICO saying:
1.) If the ‘in’ is more than the ‘out,’ you will gain weight.
2.) If they are the same, your weight will stay the same.
3.) If the ‘in’ is less than the ‘out,’ you will lose weight.
CICO isn’t going to have all the answers, but that doesn’t mean it’s useless or wrong. For example, if we see the “out” being below the “in,” then while CICO may not directly give us all possible reasons why, we can infer that something like increased fat storage and/or lessened metabolism may be happening.
The ancient Greeks figured out that the earth was not flat, and they proved it pretty well. There was quite a bit of stuff they didn’t know, and that condition has persisted - there are still things we don’t know about gravity, for example. None of this means that the earth is flat.
You can make up similar stuff for almost anything. If you want better answers, then the questions need to be different. With respect to dietary and physiological things, maybe CICO has the answer and maybe not. Its limits don’t mean it’s not correct up to those limits.
Well, there’s #1 - If the ‘in’ is more than the ‘out,’ you will gain weight. Does that not make sense?
To me, this has to be intuitive, i.e.
It makes a difference how your statement reads. If you had said, “for some reason, CICO is totally acceptable as the (or better yet, the only) explanation for obesity,” then I would disagree.
