Introduce yourself
Tell Chris Powell who you are and what your problem is. Outline for him how you came to be overweight and out of shape. Let him know about the trials and tribulations your weight causes you on a daily basis. Hammer this home.
Include photos
Send Chris photos - of you in happier times, of you now, of you with your loving family. These will probably be used on the show if you're picked.
Talk about the future
Tell Chris how much it would mean to you to get in shape and live a healthier life. Emphasise how determined you are to make this happen.
Good luck, xc