Scientists at the UCLA Neuropsychiatric Institute suggest leptin promotes the development of grey matter in the brain that regulates cravings, and may play a role in modulating personal behaviour.
As such, they conclude that leptin replacement therapy could play a major role in boosting weight loss for the 'morbidly obese'.
Propelled by rising figures for obesity, government, industry and healthcare sectors are all working to articulate strategies to prevent this physical state that can lead to a host of (expensive) illnesses, from heart disease to diabetes. Fresh figures released in March show in excess of 200 million adults across the EU may be overweight or obese.
And the number of European kids overweight is rising by a hefty 400,000 a year, according to the data from the International Obesity Task Force (IOFT).
Discovered in 1994 by Jeffrey Friedman and colleagues in the US, leptin first gained widespread attention as a "satiety signal" or appetite suppressant.
Initial studies revealed that the hormone, which is produced in fat cells, travels through the bloodstream and interacts with receptors in the brain to provide a "signal" that the body has consumed enough food and should stop eating.
Since then scientists have demonstrated that leptin's role is not confined to suppressing appetite.
Leptin receptors have also been identified in the T-cells of the immune system and in new blood vessels; as well as playing an important role in metabolism.
For this latest study, researchers used magnetic resonance imaging (MRI) to scan research subjects' brains prior to beginning leptin replacement treatment, and again at six and 18 months after treatment began.
"After receiving leptin replacement therapy, research subjects with a recessive mutation in the obesity (ob) gene - a population both deficient in Leptin and morbidly obese - lost about half of their body weight while regulating their own food intake," report the scientists.