If a drug allows the user to eat more, no physical limit could have been reached, only a willpower limit.
Does the appetite stimulated brain have to be ability to increase (or decrease) stomach capacity, speed up(or slow) digestion, generate more (or less) saliva to transport food, in addition to altering the senses to make food increasingly (or less) appetizing and occupy a greater (or lesser) proportion of thoughts, like a smoker daydreaming about a cigarette break? Of course not.
That's all absurd. There's no coordinated, potent biological system like that in place to compel you to eat more (or less).
Appetite is purely psychological and subordinate to willpower. Everyone's appetite is the same. The choice to eat is entirely within our control. If a drug lets you eat more, then you didn't hit any "physical" limit.
Put the drugs back in the bottle and the food in your mouth. I'm getting tired of these weak willed guys bitching about not being able to eat enough, how they'll vomit or can't force themselves to swallow when suddenly, with a "crutch" they can do it.
Stop using a drug to cheat. If you need that "crutch" to get the body you want, you don't deserve it.
/s