Disclosed is a phenyl boronic acid compound represented by Structural Formula (I): Ar is a substituted or unsubstituted aryl group. Z and Z' are independently -O-. -NH- or -S-. X is an electron withdrawing group. R is a substituted or unsubstituted straight chained hydrocarbyl group optionally comprising one or more amine, ammonium, ether, thioether or phenylene linking groups and Y is -H, an amine, -[NH-(NH2)q]-NH2, halogen, -CF3, thiol, ammonium, alcohol, -COOH, -SO3H, -OSO3H or phosphonium group covalently bonded to the terminal position of R. Each -NH- in -[NH-)CH2)q]r-NH2 is optionally N-alkylated or N,N-dialkylated and -NH2 in -[NH-(CH2)q]r-NH2 is optionally N-alkylated, N,N-dialkylated or N,N,N-triakylated. q is an integer from 2 to about 10 and r is an integer from 1 to about 5. R1 and R1' are independently -H, an aliphatic group, a substituted aliphatic group, an aryl group or a substituted aryl group, or, taken together, are a C2-C5 substituted or unsubstituted alkylene group optionally comprising an amine linking group [-N+(R1a)-]. Each R¿1?, is Structural Formula (I) is preferably -H. R?1a¿ is-H, alkyl, substituted alkyl, phenyl or substituted phenyl. Also disclosed is a method of treating obesity in a subject by administering an effective amount of a compound represented by Structural Formula (I) and a pharmaceutical composition comprising the compound and a pharmaceutically acceptable carier or diluent.