Weight does not give you all the information.
Weight and BMI are two measurements used to monitor body composition. You easily read your weight when you step onto a scale. The BMI, your body mass index, uses a formula that compares your weight to your height. The BMI number signifies whether or not you're at a normal weight for your height.
Easy Does It
Measuring your weight is a very simple process. Most scales are electronic. You turn on the scale, step onto the platform and wait for the electronic read-out of your weight, which is typically given in pounds. Calculating your BMI takes more effort. You need the weight from the scale and also a measurement of your height in inches. Then, you input the numbers into a computer-based program, or you cross-reference your height and weight on a chart to determine your BMI.
Limits of Each Method
Your weight may vary from scale to scale and from day to day. If you consume a greater amount of food and water, or don't evacuate regularly, your weight fluctuates, although this doesn't signify any change in fat or muscle weight. The BMI calculations are accurate, depending on your weight. However, the number may be limited in differentiating between high levels of fat weight and high levels of lean body weight. For example, bodybuilders may have higher BMIs due to the increased level of muscle, but the BMI formula considers it only as a higher weight.
You may not need the scale or BMI to tell you that you're overweight. Most people know by the way their clothes fit or by their decreased energy level. On the opposite side, a very thin person can have a body fat percentage that is unhealthy. Your weight is the first step in calculating your health risks. If your weight is high, you're at risk for cardiovascular disease, stroke and diabetes. The BMI measurement is the next step for health screening. Similar to increasing weight, as the BMI number increases, so do your health risks for high blood pressure, heart disease, diabetes and stroke.
When weight loss is your goal, measuring your weight is an indicator of your progress. As the number on the scale decreases, your health benefits improve. This correlates to a decrease in your BMI measurements as well. BMI is a good monitoring tool of your fitness progress. Both tests are easy to do on your own without the help of a certified professional and don't cost money, so are easy on your pocketbook.