Method and system for ablating selected portions of the gastrointestinal (GI) tract to provide therapy or alleviate symptoms for GI tract or liver tumors, obesity, motility disorders, GERD, or to induce weight loss. The ablation procedure may be performed endogastrically via mouth and esophagus in an anesthetized patient. Alternatively, the ablations may be performed epigastrically using laproscopic tools. The ablation may involve one of the following: a) ablating tissues of the gastrointestinal (GI) tract; b) ablating tissues of the liver; c) disruption of pacemaker region of the stomach; d) disruption of muscle layers of gastric wall; e) vagal nerve(s) disruption; f) ablation of endogastric lining for cells that produce the hunger hormone ghrelin; and g) disruption of enteric nervous system. The technology used may be one from a group comprising: 1) Radiofrequency catheter ablation; 2) Radiofrequency ablation using an irrigated tip catheter; 3) Microwave ablation; 4) Cryoablation; 5) High intensity focused ultrasound (HIFU) ablation; and 6) Laser ablation.