Though it may be nearly impossible to fancy, there was an era when spare body fat wasn't looked down upon in any way; in fact, spare body paunch was once thought of as an indicator of prominence. The belief went that someone with body fat possessed the intangibles to eat freely and to eat freely on a typical basis. It should be kept in mind that this perception was in place during an era and in regions where food deficits and food lack could and did take place.
Circumstances have assuredly changed.
Excess body weight, especially in Western culture, is not only no longer considered favorable, there's now a strong negative stigma attached to it. This stigma is reflected in the reality that, in most of the West, food is plentiful and easily accessible (though not always easily had, depending upon a person's circumstances). But food plenty isn't the only reason for a change in perceptions about excess weight. Two other reasons also provide explanation: it's now common knowledge that excess body weight is unhealthy; and the media regularly displays imagery of thin people.
The media's show of thin is a powerful image-maker. The visual of slender bodies, often presented in highly desirable ways, leaves a strong impression. And the media shows these visuals over and over again, so the impression is maintained.
This isn't meant to imply the media is using imagery to somehow poison society's consciousness. We must all take responsibility for what we believe in, and how we act upon our belief systems. Still, it's fallacy to believe the media's vast reach fails to affect opinion.
Generally speaking, the media's portrayal of the thin, sculpted body type is used for commercial purposes. The media wants to present a desirable image and attach a product to it. They want to sell, and they're using body type to do it.
But problems can occur when people attempt to emulate the "perfect" body type they see in the media. Eating disorders are a possible outcome. The widespread nature of eating disorders within Western culture is certainly related to extensive media imagery of thinness, and the inference that a thin body is particularly desirable.
There is additionally the emotional distress and suffering experienced by people with a body type that's different from slender. Heavy persons are sometimes subject to psychological beatings because of their figure. They're at the other end of the epitome. They're beneath others -- or so the assessment and the behavior sometimes goes.
A healthy body is a good thing. A fit body is a good thing. But, though it may be difficult to do in the face of so much feedback, each of us must develop our own value system as to what's a desirable body type, and what is not. If we let the media create this value system for us, we put ourselves in a vulnerable, and potentially damaging position.