I weigh the same as I did when I was 18 (110 lbs - 5'4")...50 years ago.
Pssst....COUNT CALORIES!!!
I think portions/calories is the main answer- I remember growing up people ate MUCH smaller portions. Of course I do believe people need to watch out for carbs, but think they are also ok in moderation with a healthy diet. When restaurants began to serve huge portions people began to eat larger portions of everything even at home. Junk food became more common and people just went nuts. I am not blaming restaurants or the food companies in any way, people just need to be more sensible.