Are 15 inch biceps big for a 4'11" woman that weighs around 90 or 91 pounds?

When I bend my arms they look really wide flattened, when extend them they don't look as bad, but I still have a little flab. Is this normal? Or is this a sign that i need to exercise? I also have a 29 inch waist that has rolls. How can someone like me have wide arms and waist? Am I fat? because every bmi... show more When I bend my arms they look really wide flattened, when extend them they don't look as bad, but I still have a little flab. Is this normal? Or is this a sign that i need to exercise?

I also have a 29 inch waist that has rolls. How can someone like me have wide arms and waist? Am I fat? because every bmi calculator, chart and doctor says i am underweight. If that's the case, then why the flab?
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