The specific number of calories you need to maintain a healthy body weight will vary based on a number of factors, including your age, gender, and activity level. Some example calorie requirements:

To lose one pound, you need to burn off 3,500 calories more than you take in. The best way to burn off those calories is a combined diet and exercise approach. Increased activity is good for you, and trimming unnecessary calories is good for you as well. But doing both is best for your overall health.