Planning to lose weight after the holiday season

I'm sure everyone will be be busy attending family and friends gatherings soon for christmas is coming.We are usually invited or we are the one who invite.This time,we are invited by my 2 sister in laws in two different dates,in my mother in law's house and the last stop will be on the new year's eve in my friend's house.No doubt,it will be a non stop eating festive foods.But after that,I plan to lose weight and might use a diet pill.But the question is,what is the best diet pill for me?I wanted it to be safe for my health and is effective.Maybe I'll just ask an advice to my doctor.