These pills interfere with the body systems and result in nutritional deficiencies, particularly of iron and calcium, the researchers said.
"In growing children and teenagers, even a marginal reduction in energy intake can be associated with growth deceleration," dailymail.co.uk quoted the Canadian Pediatric Society researchers as saying.
Weight loss pills are advertised as the quick solution to shedding pounds and obtaining the perfect figure, but they come with potentially dangerous side effects, including increased heart rate, fainting, unusual bleeding and heart attacks.
Diet pills can also cause and, in extreme cases they can rip apart the stomach lining and even lead to death, the study showed.
Further, researchers from the University of Minnesota said a startling 63 percent of teenage girls use "unhealthy weight control behaviours" to maintain a slim shape.
About 22 percent of teenage females use "very unhealthy weight control behaviours".
The use of diet pills in teenage girls had a significant spike in a five-year span, jumping from 7.5 percent to 14.2 percent in 2006, they claimed.
Instead of turning to diet pills, exercise, changing eating habits and drinking more water, mediation, are other healthy ways to lose weight, the researchers said.