The presence of lean mass (LM) deficits in pediatric patients with IBD is well established, and these deficits persist despite achievement of remission and restoration of body mass. LM deficits are associated with negative health outcomes including decreased physical function, metabolic dysregulation, increased risk of infection, and reduction of bone mass. These deficits are multifactorial though largely explained by chronic malnutrition due to enteric nutrient losses, inadequate dietary intake, malabsorption of nutrients, and increased energy needs.