I'm not sure how much he weighs, and I don't have an acurate scale so I can't weigh him. But I can easily feel his bones (but not see them), and some knowlegable people have said that he is a bit underweight.
No new food, environment, or anything like that.
He is 4 years and 4 months old, I've had him since he was 10 weeks or so.
He has a cagemate, a 1 year 3 months old boar, they've lived together for about a year, without any problems.

The pigs get their foodbowl filled with pelletfood every day, about 1 cup of veggies, unlimited hay, and lots of treats. They also have a bowl of rolled oats out all the time that gets filled frequently.

Tizzy eats ALOT, that isn't the problem. In fact, he is a very greedy boy.