spare tyre
1. A layer of excess fat around one's midsection. Primarily heard in UK. I think I need to lay off the lager, because this spare tyre of mine is getting a bit out of hand.
2. An unhelpful, unnecessary, unproductive, or unwanted person in a group. Primarily heard in UK. There are a few spare tyres on this project who are really holding back our progress. Ever since John's girlfriend started hanging out with us, it's left me feeling like a spare tyre.