Skinniness is still valued in the fashion business.

How specific sizes translate into dimensions has altered over time and varies significantly from brand to brand and garment to garment, which is one of the reasons millions of women struggle to find clothes that fits. Last month, at the Chanel couture show in Paris, one model stood out from the rest of the models on the runway. Jill Kortleve is stunningly gorgeous, with almond-shaped eyes, heavy bushy brows, and sculpted cheekbones. Since her ....