Is A Candy Bar A Day A Health Risk For Autistic Man?

Can someone with a medical background please tell me the health risks for an Autistic male, 26 years old who eats a movie theater size Butterfinger and Pepsi a day, and has done so for at least a year. Also, he drinks no water, only a great deal of soda. He does not understand the importance of nutrition, only what he likes and his mom gives him only what he likes (greasy foods, sweets and soda). If there is no health risks I will back of, but if he is in jeopardy I will advocate for him, even though his mom will resent me.