Is BMI accurate to assess one's fitness

BMI is determined by this equation: A person's weight divided by his or her height squared. Generally a BMI of 25 or above indicates a person is overweight; 30 or above indicates obesity. BMI is an arbitrary, essentially flawed, archaic load of old twaddle that can't differentiate between fat and muscle mass. It is a wholly unreliable indicator of health. BMI is not perfect. For example, it's very common for kids to gain weight quickly - and see the BMI go up - during puberty.

BMI is a notoriously unreliable measure of health. In fact, a few years ago they actually lowered the "healthy" range. BMI is a reliable indicator of body fatness for most children and teens. BMI does not measure body fat directly, but research has shown that BMI correlates to direct measures of body fat, such as underwater weighing and dual energy x-ray absorptiometry (DXA). BMI is a measure which takes into account a person's weight and height to gauge total body fat in adults. Someone with a BMI of 26 to 27 is about 20 percent overweight, which is generally believed to carry moderate health risks.

BMI is not the whole story when it comes to someone's weight. A more muscular kid may have a higher weight and BMI but not have too much body fat.