 Every patient proposed for major elective digestive oncologic surgery will be invited to a nutritional assessment. Exclusion criteria will be emergency surgery or renal failure serum creatinine over 1.5 mgdL. Some patients will not accept or will not be able to attend for several reasons, however they will be assessed by the clinical nutritionist the day of admission, before entering the OR, and followed as the other study patients, and will be considered the control group. Nutritional assessment will include clinical story, dietary recall, Global Subjective Assessment GSA, calculation of percent weight loss respect habitual weight, anthropometric measurements height, weight, body mass index and hand grip strength. Functional involvement will be studied by the Karnofsky score. Among laboratory analysis total proteins, albumin, creatinine, BUN and blood cells for lymphocyte count will be included. All data will be registered in a special chart and then emptied in a computational data base. 