Nobody gets like that without major mental health problems. Other rappers are hooked on alcohol and drugs, he's addicted to food.
Unless he actually uses that money to get some counseling and a nutritionist he won't make it.
Also I don't want to assume he wants to live. He very much could be aware that if he doesn't make changes he will die and he feels a sense of ownership and control over that. Some people find out they have a terminal illness for example and rather than treat the illness and increase their chances of survival they refuse to treat it because they're extremely depressed and see it as "a way out".
They lie to their friends and family and say that they were told they won't survive. They get to die without committing suicide, but their refusal to prevent their death is still some form of suicide. Their family and friends just get to live on thinking that the death was something that was unavoidable and it was "his/her time"