To lose some stomach fat you should be precise with your diet and exercise. You need a proper balance of exercise, nutrition, supplements in order to lose some stomach fat. Below are some diet as well as exercise is given to lose some stomach fat in 4 weeks.
DIET AND NUTRITION
1. Improve your nutrition to mostly eat low fat protein (chicken, fish, lean turkey, etc.) and veggies (i.e. broccoli). Mix a little fruit in there for some sweetness. You can also buy whey protein and make whey protein smoothies (2 scoops protein, ice, skim milk - blend little peanut butter, ripe banana, more ice - blend again: tastes great). Cut out any junk food (especially soda, anything loaded with high fructose corn syrup, all sweets, etc.)
2. You wanna eat 5-6 small 'meals' per day as this will keep you from being hungry all the time and 'pigging' out and will keep your metabolism up.
3. Start taking some active energy multivitamins. Also, you can try a thermogenic fat burner such as Ripped Fuel (provides extra energy and helps burn fat) or Hydroxycut Hardcore...but follow the instructions (take before you workout and don't exceed the daily allowance)