Disclosed are polymers comprising one or more phenyl boronate ester, boronamide or boronate thioester groups. The phenyl boronate ester, boronamide and boronate thioester groups are represented by one of the following structural formulas: ##STR1## Ar in Structural Formulas (I) and (II) is substituted or unsubstituted; and each Z is —O—, —NH— or —S— and is independently selected. Pharmaceutically acceptable salts of the polymer are also included. The aryl boronate ester, boronamide or boronate thioester can be cleaved to release the corresponding aryl boronic acid. Also disclosed are pharmaceutical compositions comprising the polymers of the present invention and a pharmaceutically acceptable carrier or diluent; and methods of treating a subject for obesity with the polymers of the present invention.