Glycyrrhetinic acid, the active principle of licorice, can reduce the thickness of subcutaneous thigh fat through topical application.

Cortisol is involved in the distribution and deposition of fat, and its action is regulated by the activity of 11beta-hydroxysteroid dehydrogenase. Glycyrrhetinic acid, the active principle of licorice root, blocks 11beta-hydroxysteroid dehydrogenase type 1, thus reducing the availability of cortisol at the level of adipocytes. We evaluated the effect of topical application of a cream containing glycyrrhetinic acid in the thickness of fat at the level of the thigh. Eighteen healthy women (age range 20-33 years) with normal BMI were randomly allocated to treatment, at the level of the dominant thigh, with a cream containing 2.5% glycyrrhetinic acid (n=9) or with a placebo cream containing the excipients alone (n=9). Before and after 1 month of treatment both the circumference and the thickness of the superficial fat layer of the thighs (by ultrasound analysis) were measured. The circumference and the thickness of the superficial fat layer were significantly reduced in comparison to the controlateral untreated thigh and to control subjects treated with the placebo cream. No changes were observed in blood pressure, plasma renin activity, plasma aldosterone or cortisol. The effect of glycyrrhetinic acid on the thickness of subcutaneous fat was likely related to a block of 11beta-hydroxysteroid dehydrogenase type 1 at the level of fat cells; therefore, glycyrrhetinic acid could be effectively used in the reduction of unwanted local fat accumulation.