Average BMI in the United States increased from 25.2 in 1975 to 28.9 in 2014, so a 3 point increase. Compare an average 1975 person with an average 2014 person. It’s far more likely that the 3 point increase is due to overeating, rather than other explanations like packing on muscle (3 whole points of muscle is a lot) or variation in bone mass (this is likely negligible). Overeating is the path of least resistance in wealthy Western countries. So yes, technically BMI is not the same thing as fatness, but they are highly correlated.
Also as Rockenots points out, the direction of your height claim is going in the wrong way. BMI is an underestimate for fatness for very tall people. For example, a healthy weight 6′2″ man’s BMI might be 17 or 18, which according to the standard BMI scale is underweight. That’s why measures like better BMI exist.
Average BMI in the United States increased from 25.2 in 1975 to 28.9 in 2014, so a 3 point increase. Compare an average 1975 person with an average 2014 person. It’s far more likely that the 3 point increase is due to overeating, rather than other explanations like packing on muscle (3 whole points of muscle is a lot) or variation in bone mass (this is likely negligible). Overeating is the path of least resistance in wealthy Western countries. So yes, technically BMI is not the same thing as fatness, but they are highly correlated.
Also as Rockenots points out, the direction of your height claim is going in the wrong way. BMI is an underestimate for fatness for very tall people. For example, a healthy weight 6′2″ man’s BMI might be 17 or 18, which according to the standard BMI scale is underweight. That’s why measures like better BMI exist.