CICO has HUGE assumptions that do not hold as valid under certain conditions of disorder.
Thyroid regulates glucose control at the cellular level. CICO assumes this mechanism can never disrupted.
Insulin regulates glucose storage again at a cellular level, CICO assumes that we have an ability to sump an infinite amount of glucose into our metabolic engine, even Mark recognizes that is bullshit, necessitating his limit on carbs based on the upper limit for the human organism
when a person reaches a certain level of obesity ( i use 30 pounds over as a general rule of thumb) the equations change. in simple terms the fatter you are the less diet has an impact on your ability to reduce. the system begins to feed on itself and it takes serious intervention and exercise ISNT that intervention.