An athletic person usually has a large drop from his jacket size to his pant size, making it quite difficult for him to buy a suit off the rack. Tailored jackets are usually made to fit "office bodies", not beach bodies. As a result, the size that fits the chest is usually much too large over the stomach area.

When attempting to sell this customer off the rack, the common practice is to move him away from a suit, into a separate jacket and pants, in order to get him the correct pant size. However, you'll still have to take in the waist and seat of the jacket several inches. The end result usually won't look very good.

Have you ever taken in a pant so much that the back pockets were nearly touching? This happens because all of the material is being taken away from the back panels of the pant only. A similar effect happens when you have to take in a jacket too much through the waist and seat area, since the alteration is usually just done to the side and back panels of the jacket. When a jacket is made-to-measure, the front panel will be made smaller as well, causing the balance of the jacket to be correct, and the garment will look much more flattering on the athletic (or slim) person's physique.

The diagram below illustrates how the factory will reduce all three panels to make the waist smaller.