How to get down to pre-vacation weight??

It's been two weeks since we came back from Hong Kong... and I am still trying to lose the 2 kilograms that I put on while on vacation. Yup! I put on 2 kilograms in a week. 

What do you expect when all we did was EAT EAT EAT?
I've been going to the gym for my regular twice-weekly workout, played tennis and even swam in my very neglected pool. Yet... the weight does not seem to be shedding at all. What a bummer! I think I will have to resort to fast weight loss pills to get to my pre-vacation weight!