I do think that many beardies are over fed. As growing babies beardies are little eating machines. We hear, 30-40 little feeders per meal, 3 times a day. And the little beardies can eat that much, easily! In the wild beardies are opportunistic eaters. There is not a steady supply of crickets at their disposal. They might eat 100 bugs one day, but not see a single bug for a couple more days. That is why they eat so much at one time, their instincts tell them that there might not be any more food for a while. It's not so much of a problem when they are little and growing like weeds. All of the protein is used up as energy to grow and dart about.
As adults beardies do not need nearly as much food, especially insect protein. However owners tend to still feed their beardies alot of larger prey. And since the beardies are now big they will be offered feeders like superworms, which are higher in fat content that some other available feeders. This, along with lazy dragons stuck in a cage all day, leads to overweight dragons.
I think over feeding can be just as bad as under feeding. I know if I ate just as much as I did when I was 18 now, I'd be huge!
There's a balance there somewhere. We all know how hard it can be to get your beardies to eat their vegetables, but I think (as adults, +/-2 years old) offering them greens everyday, and feeding them insects every two or three days is healthy for dragons. One, if they're really hungry they will eat the greens. Two, they will be really excited to see feeder insects and really go after them (exercise!). And three, they will have a healthier diet.