The subject matter of the invention is a functional population of human brown adipocytes, in which the expression of UCP1, CIDEA, CPT1B and Bcl2 is higher, the expression of Bax is lower and the expression of PPAR-alpha, PGC-1alpha, PGC-1beta and PRDM16 is similar compared with the corresponding expressions of a population of human white adipocytes. The invention also relates to a method for differentiation of hMADS cells into the functional population of human brown adipocytes, to a method for conversion of a population of human white adipocytes into the functional population of human brown adipocytes, and also to a method of screening for molecules capable of modulating the bodyweight in an individual.