A coevolutionary balance exists between bacteria within the mammalian gastrointestinal tract and the lining epithelia. Recent advances in the molecular detection of bacteria have demonstrated that under normal circumstances, the lining mucosal epithelium in the gastrointestinal tract is sterile. Under conditions of stress and dietary alteration however, the probability of bacteria adhering to and altering epithelial function is a reflection of the virulence tactics of the resident bacteria balanced against the innate mucosal defense system. This pathologic event may be caused in part by the adaptive response of intestinal bacteria to their changing environment and food supply. Accustomed to a warm climate and a constant and predictable food supply, bacteria exposed to luminal nutrient starvation and a catabolically stressed host may express virulence determinants that can harm the host. The causes and consequences of bacterial adherence to host intestinal epithelia during stress and dietary manipulation are discussed.