Help Me figure out a solid plan to lose weight?

I am 16, over 190 pounds. I used to be 135 pounds but in the past year I've gained A LOT. I have the jillian 30 day shred dvd, and I can do that no problem, but it's keeping the diet going, that is hard. Please give me advice on keeping track with my diet and special tips of your own! I'm scared I'm close to be getting diabetes or some kind of heart problem (heart problems run in family)