Obesity is a direct, causative (not correlated) factor in heart disease as well as diabetes. There is ample clinical research to this conclusion.
Yes, I agree absolutely.
But defining obesity only by the classical BMI calculations clearly does not tell the whole picture, in particular for muscular individuals.
I'm 5'10", 207 lbs, which is a figure I am happy to say is slowly dropping. To be classified as "normal" by the BMI classification I must be down to 175 or lower. I don't see that happening without loosing quite a bit of muscle mass - my bulge in the middle is NOT 30 pounds of fat. No way. With regards to fitness, performance, stamina, strength and overall health I absolutely does not fit into the "obese" category, which I am bordering according to the BMI classification. I am happy to say I don't look fat - though there is a bulge in the middle if you look for it.
I work on loosing the "bulge", though. Excessive tummy fat is a pretty good indicator on the risk of developing diabetes, which runs in my family. Loosing the bulge is my best weight indicator - but when that happens my BMI will still classify me as "overweight".