Well, considering fat localizes in different areas and muscles weigh more than fat, weight is a terrible measure. A skinny man can have fat all around his organs and give him heart attack at age 40...but he's not fat. Same could be said of a man that's a body builder but considered obese according to the body mass index...but he's got a six-pac. What's the difference? Just because it has fins and swim in the water...does that make it a fish? No, it's f*king dolphin and they're mammals. In all reality, it makes all the difference.