The most athletic of you know that working out can literally change your life. Both physically and from a psychological standpoint, there are many benefits to exercising.Those for whom physical appearance is very important are constantly looking to improve. Having a flat stomach is a big goal for many athletes. But if you want to have a flat stomach, working out isn't going to cut it.The keys: weightlifting and nutritionYou can work out all you want, you'll never lose as much weight as you want to if you don't supplement your physical activity with a healthy diet. What you put into your body is your fuel. Eat healthily; you'll feel the difference in no time.If you want to have a nice, flat stomach, weightlifting is very important. Indeed, while all physical activity melts fat, specific weight training exercises can help you lose that little spare tire you have around your waist.One sport in particular: weightliftingTo lose belly fat, you need to reduce your overall body fat. The best way to do this is by lifting weights.