When you step on the scale, the Aria 2 displays your weight data and automatically sends it to the Fitbit app so you can track your progress. Your body fat percentage is shown on the right side of the scale. Compare your weight data with changes in your body composition to see if you are building muscle and burning fat. The BMI (Body Mass Index) is a measure that determines whether you have a healthy weight for your age and gender based on your height and weight. Aria 2 calculates it for you based on your weight and profile data and sends the information to the Fitbit app. Lean mass is the weight of your body without the fat component. This number helps you understand if you are burning fat and building muscle. Aria 2 sends the data directly to the Fitbit app. Set your scale to the correct mode - Normal or Lean - for more accurate statistics. When Aria 2 syncs with your app, your data is transformed into easily readable graphs that represent your long-term trends and show you if your hard work has paid off.