CICO can always be applied to the real world. People fail because they don't track their food intake properly and they use some general TDEE equation that is meant for the "average" person. People quite often miscalculate their activity level as well. Taking a 2-3 mile walk a couple times a week does not make you moderately active - it makes you lightly active. Deadlifting, squatting and benchpressing 3-4 times a week along with some moderate cardio makes you moderately active. That is far above what the typical person on this site is doing.
Originally Posted by Omni
You find out your TDEE by experimentation. Eat 1,700 calories every day for a week. If you don't lose weight, drop it to 1,600 calories. If you don't lose weight, drop it to 1,500 calories. It may take a few months before you dial it in. Most people that claim CICO "doesn't work" don't put forth the time and effort to track their food intake properly or track their TDEE properly. Don't use some general equation from a website, assume your activity level, loosely track your portions and complain when it "doesn't work." People fail the system, the system never fails because CICO is absolute.
Don't put your trust in anyone on this forum, including me. You are the key to your own success.