Maybe you could convince them to all eat healthy, I did. And my parents were proud that i asked them. So we did, although they only lasted 3 weeks, but it made it easier for me afterwards. Just having a couple of weeks with little temptations helped me to be ready afterwards. It really did work.
Also I drank so much water, whenever I felt just slightly hungry I would eat 1 rice cracker with 1 glass of water, so i never felt hungry. So that too also helped me.
Just talk to your parents, it would be good for everyone in the family. Tell them that they want to go into their twilight years healthy, not tired and wrinkly!? lol
Keep a positive attitude, listen to inspirational songs, and if you really are determined like i think you are, you'll get there.
Hope this helped, good luck.