Holiday pounds refer to the extra little bit of weight you put on during a period of being on holiday or vacation.

Holiday pounds指休假或者节假日期间额外增长的那部分体重，我们可以戏称为“假期胖子”。

For example:

Man, when I get back to work I'll have to start going to the gym again- I've put on some serious holiday pounds.

唉，等我回去上班，我得开始去健身房了，休假长了不少肉。