You hear it all the time on diet plans, from your doctor, etc. But it's apparent simplicity is both misleading and unhelpful.
Yes, CICO is true(ish, there are exceptions) But that's answering the wrong question. The question of why someone is overweight is, given that most dieters already know this, why do some people eat too much?
I'm a scientist and I hate this CICO mantra being thrown around like it's something we haven't heard before. Its unhelpful. We don't tell alcoholics that they are alcoholics because they drink too much booze. The answer to the obesity crisis lies in answering the real question.