Body mass index (BMI) is based on a formula that uses both weight and height to estimate associated health risks. It was invented between 1830 and 1850. Due to its ease of use, it is the most widely used diagnostic tool to identify weight problems within a population, whether individuals are underweight, overweight or obese. Though it does not actually measure body fat percentage, your BMI is a general measurement that can help guide you in determining a diet and exercise program.

However, the body fat percentage you get from a body fat scale or hand-held body fat device can vary depending on many factors. How warm or cold your body temperature is at the time you take the test, how hydrated you are when the test is taken. In fact, it's difficult to get an accurate body fat measurement from most commercially available body fat analyzers. A hydrostatic body fat test is the best and most accurate way to have our body fat taken. A hydrostatic body fat test is where you are submerged in water. This kind of  testing is a more exact measurement because bone, muscle and connective tissue, known as lean mass, sinks while body fat floats, giving you a more accurate measurement.