Provided are ingestible polymeric formulations and oral dosage forms for the reduction of gastric volume in the treatment of overweight and obese patients. The formulation includes an acid-sensitive, gelatin coating over a dehydrated hydrophilic polymer. When ingested, the acid-sensitive coating is quickly dissolved by gastric secretions and the hydrophilic polymer is exposed to the aqueous environment of the gastric milieu. The polymer absorbs water and expands to the point that will not allow the polymer to pass beyond the pyloric valve, and the expanded polymer is therefore trapped in the stomach.