Oleoyl-estrone (OE), or estrone 3-oleate, is a fatty acid ester of estrone. It is a naturally circulating hormone in animals, including humans. It was studied as a potential weight-loss drug, but failed to show benefit in clinical trials. It was first reported in 1996 to cause a body fat loss effect in rats in the International Journal of Obesity and Related Metabolic Disorders. The animal research has all been conducted by the Nitrogen-Obesity Research Group of the University of Barcelona. The compound was found to potently induce body-fat loss while preserving protein stores in animals which is the ultimate goal of an anti-obesity agent as body protein loss is an undesired but inevitable (to some degree) side effect of fat loss via calorie restriction. Mechanism of action Oleoyl-estrone functions by reducing energy-intake without prescribed dietary restriction (forced dietary restriction in addition to OE actually led to protein losses) while maintaining energy expenditure (which normally falls as part of the adaptations to calorie restriction). The partitioning effects of this hormone leads to adipose stores being the source of energy that makes up for the energy deficit rather than protein stores. Research The molecule has been widely studied in various strains of animals and shown to be effective in virtually all studies. A surprising result that came out of the animal studies was that OE treated animals maintained their fat loss after treatment was stopped. Weight loss maintenance is one of the most difficult aspects of obesity treatment and so this effect is promising. This led to the postulation that oleoyl-estrone can reduce the body's bodyfat setpoint which would allow the body to maintain a reduced bodyfat without experiencing a hormonal milieu that aims to regain the lost bodyfat by reducing energy expenditure and increasing energy intake. The research group discovered that oleoyl-estrone levels correlated with bodyfat stores except for obese organisms where there was less oleoyl-estrone circulating than would be predicted based on bodyfat levels. This led to the theory that administering oleoyl-estrone to bring plasma OE levels up to normal would signal to the body that there is an excess amount of bodyfat and therefore there would be a bodyfat loss. Recent research shows that corticosterone inhibits the fat mobilizing effects of oleoyl-estrone in female rats that had their adrenal glands removed. The research group set up a company called Oleoyl-Estrone Developments in 2001 which included as a founder Marià