Should I drink caffeine while trying to lose weight?

I've heard of beneficial and harmful reasons not to drink caffeine while/during/before a workout. I'm just wondering if its ok for me to do it though. I'm in pretty good shape other than I'm trying to lose belly fat but I've worked out all of my life and have pretty good stamina. I drink about a cup or so of diet soda before I workout or go on a long bike ride and I've seen slightly better results from it. I'm 17 years old in decent shape with a bit of belly fat to lose should I be drinking caffeine for my workout or am I better off physically/health-wise not taking it?