You can set how high or drunk someone is by using /set (character) alcohol (number) or /set (character) high (number) , I don't remember the actual numbers but it increases capacity for stomach and bowels for both but doesn't show on the stats screen
If you want big belly you could| set Player bowel_capacity {number} or set Player stomach_capacity {number}| so you don't have to work your way to getting max cap
but also (/set IBottleGas in_fridge 1) for gas bottles to be bought in fridge for inflation and big belly and (/set ControlEnv money 1000000) for the money