Well, if you accept the general premise of the carnivore diet, part of the theory is that its hard to overeat on protein since its so filling, and filling for so long. So if you have a relatively normal, or only modestly overextended appetite, you'll struggle to eat obesity levels of calories. The problem is that this doesn't work if your already eating such immense portions that you stomach can handle 4,000 calories of pork in a single sitting. The carnivore diet is actually pretty fucking hard if you're already morbidly obese and sedentary.
But if Jacks operating off of his brothers praise for it, and the first-page internet advice for it, the diet is the endgame, as when you ignore all the warnings, caveats, and must-do's, then it does read 'eat meat get healthy'. Jacks endgame will likely be the extreme levels of protein in his system pushing his likely fucked kidneys over the edge. Between his obesity, gluttony, and his blood sugars, they have to be already damaged, if not hanging on by a thread, and excessive protein will just strain them further. Kidney failure would be the genuine death timer for Jack - no way he gets a transplant, and even with Dialysis and carefully managed diets in otherwise healthy people, he'd be lucky to last a couple years. Much healthier people often only make it five.