What would be a good supplement to help me speed up my metabolism?

I had a baby a year and a half ago and I am still dealing with the 50 lbs. weight gain. I work a very manual job (FedEx pkg handler) which is helping me to loose it but I could use something to help pick it up. I do my best to eat healthy too. It's hard being a mom, a ft college student n to have a pt job :(