If we assume that the back of his waist is the same as the front, we're currently at 33 inches. Since Sean is a three-dimensional being, we have to account for his sides. If we conservatively estimate his thickness at 2/3rds of a basketball, we have 6 inches on both sides.
Therefore:
Front (16.5) + back (16.5) + right side (6) + left side (6) = 45 inches
Which in turn, explains why this happens:
When the first suggested result of your name is that your fat, rather than that you play professional basketball, it's probably time to re-examine your eating habits.