Enlarge Images courtesy of The Advertising Archives Dieters have been looking for a magic weight-loss cure for decades. Just look at ads from the past that promise amazing results by simply taking a salt bath, listening to a recording, eating "bile beans" or shaking pounds off with an electric massage belt. Posters showing these ads and a collection of old diet books will be on display for several months beginning today at the Library of Congress in Washington, D.C. GALLERY: Diet advertisements throughout the ages At a special event today aimed at keeping the obesity epidemic on Congress' radar, national obesity experts will discuss 150 years of dieting. "If we recognize the history of weight loss, we can successfully and smartly address the epidemic we are facing," says Karen Miller-Kovach, chief scientific officer of event host Weight Watchers. Many still think of weight loss the same way people did when those ads came out — they expect magic, says Patrick O'Neil, director of the Weight Management Center at Medical University of South Carolina-Charleston. But obesity is a complex medical problem that involves genetics, environment, biology and behavior. There is no magic pill; prescription weight-loss medications are few in number and modest in effects, he says. Still, you can slim down if you reduce calories enough, he says. But no one is saying it's easy, he adds. You have to work to maintain the loss by continuing to eat less and exercise, O'Neil says. It's no wonder that the "quest for effortless weight loss continues." Miller-Kovach, author of She Loses, He Loses: The Truth About Men, Women, and Weight Loss, notes that the old ads show only women. "When it comes to weight loss, women are diplomats, and men declare war," she says. "Women are always trying different things. They are always reading. ... They often flit about and try different things until they get the point where they get serious and do something about it. "Guys say, 'I have a problem. I need to lose weight. I'm going to lose weight,' " she says. "Then they do." We've updated the Conversation Guidelines. Changes include a brief review of the moderation process and an explanation on how to use the "Report Abuse" button. Read more