Parenting Fail!

I truly feel like a failure as a mom after Logan's 6-month medical checkup on Friday. We are not blind parents - we can see that he is a little overweight compared to his friends. However, I was not prepared to hear that he falls into the childhood obesity category. Apparently he has gained 60 lbs. over the last year. Granted, he has also grown about 5 inches taller.
Seeing as how Artie & I have both been overweight, and are still not "skinny" people even after each having gastric bypass surgery, I feel as if we have not only set a bad example for Logan weight-wise, but we have also enabled him to become so overweight. We always have snacks in the house, even if we don't have bread or milk. (We actually don't eat much bread or drink much milk, but that's beside the point). Up until about a month ago, Logan drank regular sodas by the case, practically. We finally got him switched to Diet Mountain Dew and G2, and off of regular Mountain Dew and Coke. I personally think that his sleep schedule this summer has also contributed to his "declining health." I'm certainly not a doctor, but how can it be healthy for him to stay up until 2:00 or 3:00 in the morning playing xbox and then sleep until 1:00 or 2:00 the next day?
And speaking of xbox, that is a whole other issue. Another epic failure as a mother. I let him play WAAAAAY too much xbox!! He's on it for HOURS and HOURS every day, while I'm at work, after Artie & I go to bed, and most of the time that we are at home in the evenings with him.
It seems as parents we have chosen the path of least resistance and we basically give in to whatever Logan wants. It has always been this way with buying him things, but now it is also becoming true with routines and lifestyle, as well. Once he develops a habit, it is much harder to break it than to have never let him start it in the first place.
So I have failed as a mother. Failed to set reasonable guidelines and rules, failed to provide quality food options for my child, failed to lead him in the ways of proper nutrition and exercise, and failed to be the firm guiding hand that all children need.
Going back to school next week will solve some of this issue, because his sleep schedule will obviously change. He will also not be home all day to snack and eat whatever he can find in the house. This coming weekend, Artie & I are taking the doctor's advice and cleaning out all snack food from the house. We are replacing it with fruits and healthy snacks. It will be hard on all 3 of us to do this, but it's best for everyone. And after all, what is more important - my child's health or a bag of chips?
I am really beating myself up over this. Logan makes jokes about his weight all the time, but I know that it does bother him. 8th grade is not a fun place to be overweight.
Suggestions from all the successful, qualified parents out there?