Women's magazines are (for the most part) the progeny of modern consumerism and self-hate. The woman sees them at the supermarket checkout counter - Redbook, Glamour, Elle, Vogue - complete with incredibly emaciated supermodels on the cover. The articles begin the cycle of self-hate:

"The Miracle Eat-Only-Brussels-Sprouts Diet!"
"Starve Your Way to the Perfect Body!"
"Learn the NEW Sex Technique to Drive Your Man Wild! This One's Really New! We Swear! Not Like Last Month!"
"Are You Too Self-Reflective? Take Our Quiz and Find Out!"
"Summer's New Look: Sleeveless Shirts, Bright Colors, and Suntans!"
Etcetera.

Then, ads and photo shoots pull the reader in. The see the model on the cover, and think, "Gee, I'd like to look like her." They buy the magazine for the diet articles so that they can look like her. They lose a little weight, see more pictures of even skinnier Auschwitz-victim look-alikes in the photo shoots, and buy even more magazines to lose more weight. This is mostly a Western phenomenon. People in third-world countries tend not to be seduced by thin people. They'd like to know why we all want to be thinner when their biggest problem is putting weight on.

Dislcaimer: Not all women's magazines are pro-skinny. Some offer genuinely intelligent insights, honest journalism, and darn good articles about women's issues. They just don't put those at the supermarket counter.