A compound according to formula I wherein R1 and R2 independently represent hydrogen, nitro, cyano, halogen, alkyl, alkenyl, alkynyl, haloalkyl, aralkyl, heteroaralkyl, alkoxy, alkylamino, --C(O)O--R4, --C(O)NR5R6, --S(O).sub.2OR4, S(O).sub.2NR5R6 or --S(O).sub.nR4; R4 represents alkyl, alkenyl, alkynyl, haloalkyl, hydroxyalkyl, cycloalkyl or aryl, wherein said aryl may optionally be substituted with one or more substituents selected from alkyl, halogen, haloalkyl, hydroxyalkyl, cyano, nitro or --(CH.sub.2).sub.a--NR7R8; R5 and R6 independently represent hydrogen alkyl, alkenyl, alkynyl, haloalkyl, hydroxyalkyl, cycloalkyl or aryl, wherein said aryl may optionally be substituted with one or more substituents selected from alkyl, alkoxy, halogen, haloalkyl, hydroxyalkyl, cyano, nitro or --(CH.sub.2).sub.a--NR7R8; or R5 and R6 together with said nitrogen atom they are attached form a cycloalkyl or heterocyclyl ring, optionally substituted with one or more alkyl substituents; R7 and R8 independently represents hydrogen, alkyl; or R7 and R8 together with said nitrogen atom they are attached form a cycloalkyl or heterocyclyl ring, optionally substituted with one or more alkyl substituents; n represents 0, 1 or 2; a represents 0, 1, 2 or 3; R3 represents alkyl, alkenyl, alkynyl, cycloalkyl, alkoxy or haloalkoxy, all of which are substituted with one or more substituents selected from cyano, nitro, halogen, hydroxyl, --C(O)--R4, --NR5-C(O)--R4, aryl, heteroaryl, wherein said aryl or heteroaryl may be further substituted with one or more substituents selected from aryl, alkyl, halogen, haloalkyl, hydroxyalkyl, alkoxy, haloalkoxy, aralkyl, aralkenyl, aralkynyl, --O--C(O)--R4, --C(O)--R4, --C(O)--NR5R6, --NR5-C(O)--R4 or phenyl substituted with cyano, nitro or hydroxy; Y represents --S(O)-- or S(O).sub.2--; X represents --O--, or a bond; with the proviso that the compound is not 2,6-di-tert-butyl-4-sulfinyl-(4'-nitro-benzyl)-phenol or 2,6-di-tert-butyl-4-sulfonyl-(4'-nitro-benzyl)-phenol, and with the further proviso that if R3 represent methyl substituted with cyano and another substituent, then said other substituent is not phenyl; and pharmaceutically acceptable salts, solvates and prodrugs thereof are chemical uncouplers useful e.g. for the treatment of obesity.