You are right to worry about belly fat for it is those with too much weight around their middles that are at risk for heart disease and more. Sadly, you can't lose belly fat on its own. You have to lose weight, and - sorry - belly fat won't be the first area to show progress. However, you won't lose weight well unless you are exercising too and you can ask your fitness instructor for exercises that target belly fat.
Sit-ups are the most effective, if painful, and these need to be part of an overall fitness programme, not tackled as a single exercise in isolation. A daily work-out, warm up, full body exercises leading up to sit-ups and press-ups with stretches before you finish will have the best results, but take advice from a gym. As for food and drink: well, it's no secret that beer-drinkiing soon ends with enlarged belly.
