Effective and safe reduction in visceral fat using a formula diet in a short period before highly invasive endoscopic surgery – Case series

•We assessed efficacy of formula diet therapy to highly invasive endoscopic surgery.•The decrease in visceral fat area ranged from 17.0% to 40.7% (p = 0.03).•It should be emphasized that there were no more serious life-threatening cardiopulmonary complications.•Preoperative formula diet therapy may be an effective means to reduce visceral fat.