If he hasn't been dewormed, or you think there might be a chance of that, I'd have a stool sample checked by the vet. His increased appetite might be a coincidence or as Prin said, there are plenty of overweight labs. I'd also work on his training so he's not begging, that's fairly easily corrected (see Training threads)
"Make the most of yourself, for that is all there is of you"
Ralph Waldo Emerson
~Those who KNOW better are responsible to TEACH better~
Jenn, Simon and Peaches