It’s actually much more complex than CICO. Your metabolism shifts as you lose weight and at a certain point it gets harder and harder to lose each additional pound. If you gain weight back (as most people do) your metabolism doesn’t have a corresponding increase so weight cycling actually results in more weight gain over time than making no changes. The hormones that control hunger are also affected by weight cycling and you can get hungrier the more you crash diet and it is HARD to do anything else competently while experiencing hunger pains. So, it’s not really simple math, there are so many more variables at play than simply calories in and calories out.