Impact of Exclusion Diet in Addition to Anti-TNF Therapy in Crohn's Disease and Ulcerative Colitis: a Prospective, Randomized, Double-arm, Open-label Study

This is a prospective interventional, single-center, double-group, open-label study. Primary objective is to compare the efficacy of CDED in addition to anti-TNF therapy in active CD and UC versus anti-TNF therapy alone. Secondary objective are: * Endoscopic response * Endoscopic remission * Early and late efficacy and persistence of benefits * Biochemical response * Sonographic improvement * Tolerability and compliance to the Crohn's Disease ExclusionDiet (CDED) * Quality of life-Safety of the combination of biological therapy and CDED. The subjects considered are adult patients diagnosed with moderate-to-severe Crohn's disease or moderate-to-severe ulcerative colitis who are starting therapy with an approved anti-TNF agent (infliximab and adalimumab for both UC and CD, and golimumab only for UC).