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，大家可以戏称为假期胖子。
For example:
Man, when I get back to work Ill have to start going to the gym again- Ive put on some serious holiday pounds.
唉，等我回去上班，我得开始去健身俱乐部了，休假长了不少肉。