You only lose weight if you use more than you take in, which is why diet is the #1 factor for weight loss (you can't exercise away a bad diet.)
Regardless, though, you'll build your muscles. How much depends on what kind of exercise you're doing. Low reps and high weights build bulk, while high reps and low weights build lean muscle. Think body builder vs. runner.
muscle weighs more than fat, you your not trying to lose weight your trying to lose fat. get a tape measure and measure your stomach to see yourself slim down. and as long as you are feeding your muscles with well balanced meals and continual workout you should slim down rather fast. depending on your body at the moment.