You know those sketchy diet pill ads with the "before and after" pictures that are so obviously fixed up? In the "before" picture, the scowling woman wears no makeup and has shoved out her flabby stomach. Then in the "after" picture, she's smiling sweetly, made up perfectly, and totally sucking in her stomach. Everyone can tell those pictures are fixed up. But what about when you're visiting a plastic surgeon? Are their "before and after" shots doctored up, too? Researchers in Canada and Australia wanted to figure out how easy it was to tamper with a "before and after" shoot.

What the researchers wanted to know: Can shifting the position of your face a little change the way you look in a photo?

What they did: Researchers found three subjects who had never had plastic surgery and photographed them. Although factors like lighting, background, and distance from the camera were all kept the same, the researchers repositioned the participants in each photo. They stuck out and pulled back their heads about two centimeters, and they flexed and extended their necks between five and ten degrees from normal. Then 20 surgeons and nurses who didn't know what the test was for examined the photos and filled out a survey about each of the three participants, evaluating the changes between each photo.

What they found: Although the participants changed the position of their heads only a little, the evaluators thought their faces looked different in each of the photos. The researchers recommend the adoption of standardized photo practices so that "before and after" pictures aren't so deceptive: the same background, lighting, and body-position should be used—making marks on the floor or wall can help—and the camera lens should be at the same height as the center of whatever it is that you're shooting. They even recommend a technique called "the Frankfort plane," whereby you measure from certain parts of the body (like the "infraorbital rim," whatever that is) to make sure the body is in the same position.

What this means to you: If you're thinking about cosmetic surgery, be careful when you look at "before and after" pictures. They are often misleading. The participants in this study didn't have plastic surgery, but by flexing their neck, they could make it look like they had in the photo.

Caveats: Researchers only tested three people—but then it probably isn't that hard for anyone to squish their head the right way.

Find out more: All about plastic surgery at MedlinePlus: www.nlm.nih.gov

Read the article: Sommer, Doron D., et al. "Pitfalls of Nonstandardized Photography in Facial Plastic Surgery Patients." Plastic and Reconstructive Surgery. July 2004. Vol. 114, No. 1, pp. 10–14.

Abstract online: www.plasreconsurg.com