Do you have first-hand experience with being overweight and/or losing a significant amount of weight?

I think you're vastly overestimating how much of this (particularly "calories out") is under voluntary control. We're discussing an article that showed that extra active calories burned tend to lead to a compensatory reduction in resting metabolism.

And there are some very strong psychological/physiological drives that influence "calories in" (read up on the Minnesota Starvation Experiment for examples).