Why can't I get motivated?

I have snuck a peek here and there at the grandest of all health and life style change books, Fit for Life. I just have no motivation. I am in a classic catch 22 at this point. I'm depressed with my weight and really believe that my disgusting eating habits and sad lack of motivation when it comes to exercise are affecting my health. Yet since I am sluggish and depressed I can not seem to find the umph one needs to start a major life overhaul of the magnitude that I need.