Fage fat free or their full fat Greek yogurt are good alternatives to other yogurts which are low fat but loaded with sugar. As for your parents, Try suggesting certain foods which would be better for you, lower in sugar therefore helping to reduce your blood sugar levels etc, go shopping with them and show them what to look for on the labels. Failing that, do your own shopping. When at home if they give you a sandwich just take the top slice of bread off and eat the rest (as an open sandwich). Good luck!