Non-prescription weight loss aids are growing in significance as more consumers battle with obesity.

According to a survey of more than 14,600 adults reported by Reuters Health, about 18% of women and 8% of men trying to shed weight have used non-prescription supplements in the past two years. The researchers estimated more than 17 million Americans used such products between 1996 and 1998.

The findings highlighted the need for doctors to find out about these supplements and enquire whether their patients are taking them when they are consulted. Since many non-prescription drugs are herbal-based, people often neglect to tell their doctors they are taking them.

Yet some of them contain ephedra, a herbal stimulant believed to have caused several deaths and problems in people suffering from high blood pressure, diabetes or heart disease.

Significantly, there is little evidence that these products actually help people lose weight, lead researcher Dr Heidi Michels Blanck told Reuters Health.