A new app that lets users shed virtual weight so their faces look skinnier on "selfie" photos is raising concerns about health and body-image issues.

SkinneePix, for iPhone and Android devices, can trim from five to 15 pounds (2-6 kg) of virtual fat for a slimmer selfie look.

"Cameras add additional weight to photos and when you're taking a selfie you're also dealing with bad lighting, angles, close-ups and a lot of other factors that make people complain that the photo isn't an accurate representation of themselves," said Susan Green, co-founder of the Phoenix-based company Pretty Smart Women that created the app.

It was originally designed to help overweight adults show a leaner version of themselves, but Robin J Phillips, the other co-founder, said the app has also motivated people to lose weight.

"It's a good reminder to get off the couch, turn the TV off, and go for a walk," she said.

But some critics fear the $1.99 app, which only works on single head shots, could encourage an unhealthy body image.

Lauren Dickson, a social worker in the eating disorders and addiction clinic at the Centre of Addiction and Mental Health in Toronto, said the app is one of many factors that could contribute towards a young adult developing an eating disorder.

"The media obviously has some effect on people developing eating disorders, but it's not the only variable. It's one of many factors," she said in an interview.

"The majority of young girls wouldn't develop an eating disorder because of an app like this, but some might be more vulnerable and it could contribute," Dickson added.

Green said the virtual weight loss in the app is capped at 15 pounds and the app focuses only on the face and not the entire body.

"We definitely understand that people can have body image problems and we're not trying to contribute to that in any way," she said.

"I think if someone who is very thin uses it and goes straight for 15 (pounds), then that's probably not the best thing, but they could also do that in Photoshop," Green added.

Other apps can also add or remove weight, including one called FatBooth. - Reuters