Body Pump is a wonderful class ! I do it every week. Can a person get results ? Yes, but you won't see them overnight. In general, figure 6-8 weeks before you see a change or any kind. That really is typical.
Most people don't see dramatic changes doing Body Pump or any other class once or twice a week. And you shouldn't do Body Pump more than that. You must give your muscles a chance to rest and recover between workouts. If you don't let them rest, you risk burn out, injury and fatigue.
Ultimately, if you're trying to lose weight, you need to be mindful of what you eat. Good nutrition is what takes the weight off and keeps it off. Exercise is what keeps our bodies fit and healthy.
So, if you combine your Body Pump class with healthy eating habits, the weight will come off with time. Once again, don't expect results overnight. It won't happen.