Well, I can't speak to the hiberation part, never done that.
As far as putting some weight on him, how much & how often does he eat? My male looked skinnier than I thought he should (after a 2 week visit from my female LOL). I had been feeding every other day as is often recommended for adults. But, my adults definately like to eat every day.
I started feeding him everyday and added Superworms to his diet. He started fattening up nicely pretty quickly. I do vary his diet. He gets 2-3 superworms every other day along with his mealworm dish and the other days he eats about 6 crickets with his mealworm dish. I leave 10-12 mealworms in his dish each day, he usually eats most if not all of them. He also gets a treat of 2 waxworms on Sundays LOL
My female will only eat mealworms if I drop them one by one on the floor of her tank and they move, crickets & superworms are her favorites. She gets crickets at every feeding and 2-3 Superworms every other day. She will eat upto 10 crickets at a time. The days she doesn't have superworms I do the mealworm thing with her. And she too gets 2 waxworms on Sundays 
I'm still debating about trying silkworms as I know they are nutritionally the best for Leo's, I just hate that I have to order them on the internet. I don't like being dependant on getting a staple food for my Leo's like that. If they were available locally I wouldn't hesitate.