The real answer to this question is going to be 15-18% body fat for fashion models and for swimsuit models 16-22%. I could waste my time arguing about some of the things people post on the Internet about retouching, but no-one retouches on the runway where the models have to walk down the runway in real time. The majority of magazines are using beautiful looking girls no doubt but many of them are what are considered centerfold/pinup models. They are more curvier and bustier. That means they have more body fat and at times that body fat tens to concentrate in certain areas. So Maxim retouches, pushes in, stretches, and darkens cleavage. But do not believe that every woman you see in a magazine has been totally photoshopped. Yes, we may remove a zit, a bruise, or some stray hairs, but if someone has stomach fat, they are not cast for a shoot. Does this lead to girls and women thinking they don’t measure up? Unfortunately it does. Just like when a skinny boy looks at a Muscle and Fitness magazine. (For some reason no one ever talks about how much junk young men stuff in their bodies trying to put on mass while destroying their livers in the process). But supermodels work hard for their bodies and should be given credit for it.

Source: What is the approximate body fat percentage of female fashion models and supermodels? – Quora