Oh dear, I'm in trouble

We have been looking after this guy for a couple of weeks. Today, to     coincide with his mum coming, he became unwell so of to the vets we go. Nothing serious, antibiotics should solve the problem. What will not be solved by tablets is the fact he is about a kilo heavier than he was. Well he is a lot hairier now, and he is a bit wet because its raining and it is a heavy lead and harness he is wearing and lots of other reasons I will think of given enough time. It's nothing to do with him being over fed and under-exercised honest.