One of the first steps to realizing if you are leading a healthy lifestyle or not is determining if you are overweight. Calculating your Body Mass Index or BMI is an excellent first step. Once you've determined what your BMI you can use a combination of exercise and nutrition to help you reach your desire weight goal. If you are trying to lose weight or just maintain a healthy weight, you should understand the connection between the energy your body takes in and the energy your body uses. Energy is taken in through food you eat and beverages you drink. Energy is used by activities performed. To lose weight you have to use more calories than you take in. To maintain, you have to match the calories you take in with those that you use. Eating a healthy diet and being physically active can help you reach either goal. The number of calories you need each day depends on your age, activity level and whether you are trying to lose, gain or maintain your weight. Your diet should include the most nutritious foods including fruits, vegetables, whole grains and fat free or low fat milk and dairy products. Foods should be rich in vitamins, minerals, fiber and other nutrients. You also must be physically active. Regular physical activity is important to your overall health and fitness. It can help you control your body weight. Aim to be physically active at a moderate intensity for at least 30 minutes a day. Increase the intensity or amount of time you exercise to have greater health benefits. Children and teenagers should be physically active for at least 60 minutes every day. To see if you are at a healthy weight you can measure your BMI (Body Mass index). To calculate your BMI, multiply your weight in pounds by 704, and then divide by the square of your height in inches. For example: if you weigh 162 pounds and are 69 inches tall, your BMI is (162 x 704) divided by (69 x 69)= 23.9 which is normal. Underweight=