Fortunately, weight doesn't go on licenses in TX!
But, I have done this! When I lost weight 10 years ago (and have since gained & relost most of it), I went to the DL office for the sheer reason of getting a new picture. I still have that picture on my license.
I just looked at it, I think my face looks thinner NOW than in the picture. Hmmm, maybe a new picture will be in order.