Oh, how silly! The Dursleys are cartoon characters, and the fact that Dudley and his father are fat is meaningless.
I must say that I think one of the great weaknesses of Rowling's writing is that she mixes these one-dimensional, predictable, no-known-motivation characters with real and complex ones. It makes parts of the books really drag, while you wait for a human being (Harry Potter, Severus Snape, etc.) to show up among the cutout figures.
I don't know; I love all the books and probably should be added to the ping list (Retrokitten, you there?).
I've read all of them, very slowly, to my oldest son out loud at night. Takes us months to go through them, and we relish every bit. I think at the end of the last one, I grabbed it and finished the last 50 pages on my own, and then gave it back to him. :)
The movies are fun, even if the actors are growing twice as fast as the characters (seeing that there is a 2 year rotation of movies).
One of the guys in Malfoy's "gang" is fat, I think, too, and is portrayed as a clumsy dolt.
/sarcasm