I'm so very sorry for your loss. I know how that is. I lost my grandfather five years ago, and lost my grandmother back in February. The best I can tell you is to remember that he's watching you, and while it's fine to be depressed and greive, you have to think "What would Grandpa say if he saw me right now?" I know that helped me with the loss of my grandmother. I had to get through a full week of school before being able to grieve for her. And what kept me going was waking up every morning and saying "What would Grandma Ellen say if she saw me right now? She'd say 'Keep going sugar. You'll have time to grieve. Get that school work done so you can come visit me.'" And I kept going. Get back to whatever you were doing to lose that weight, focus on your life right now as it is, and never forget: Their lives may have left us here on earth, but their souls are always watching us from the Summerland. They can see us succeed. The only time we can ever fail is if we fail to keep living. Keep their spirit alive, remind ourselves of the impact that they left on our lives.
Blessed be, sister. You can do this.