LEP and obesity disorder: Leptin concentrations are associated with obesity types, either characterised by leptin resistance (high leptin levels) or by leptin deficiency (low leptin levels) [23] and thus, it is crucial to know the underlying cause of the condition to decide on the most appropriate course of action; therefore, classifying the type of obesity based on circulating leptin levels could provide support to decide on the best therapy, as well as providing insights into its efficacy.