For even more impressive effects on body composition: aim for exercise forms which elicit a positive hormonal response. This means lifting really heavy things (strength training), or interval training. Such exercise increases levels of the sex hormone testosterone (primarily in men) as well as growth hormone. Not only do greater levels of these hormones increase your muscle mass, but they also decrease your visceral fat (belly fat) in the long term.
Jim said people can healthily lose half a pound to two pounds a week. In a month, that could add up to four to eight pounds lost. Since one pound of fat equals 3,500 calories, to lose one pound a week, you would have to burn approximately 500 extra calories a day. This can be achieved through eating in a healthy calorie deficit or working out to burn extra calories (or a combination of both). Other lifestyle factors also play a role. Getting enough sleep will ensure your body recovers well and that you'll be energized for your workouts the next day. And too much stress increases the stress hormone cortisol, which can increase your cravings for caloric refined carbs and comfort food, which will prevent you from losing weight (especially in your belly). Make sure, in addition to eating in a calorie deficit, that you're also getting at least seven hours of sleep a night and managing your stress.
Sure, you can lose weight quickly. There are plenty of fad diets that work to shed pounds rapidly -- while leaving you feeling hungry and deprived. But what good is losing weight only to regain it? To keep pounds off permanently, it's best to lose weight slowly. And many experts say you can do that without going on a "diet." Instead, the key is making simple tweaks to your lifestyle.