Background: Dietary lipid absorption by the intestine is essential for systemic lipid homeostasis. We previously demonstrated a role for Dennd5b in intestinal lipid absorption. In humans, DENND5B gene variants are correlated with BMI in females, but not males. Female Dennd5b -/- mice have reduced appearance of dietary triacylglyceride (TAG) in plasma and are resistant to diet-induced obesity, however, the metabolic impact of Dennd5b -/- in male mice has not been reported. In this study, we test the hypothesis that the Dennd5b -/- mouse model recapitulates the sex disparity observed in humans with DENND5B polymorphisms. We also investigate the fate of unsecreted intestinal TAG in this model of impaired dietary lipid absorption. Methods and Results: A non-absorbable fatty acid (FA) tracer was used to quantify the impact of Dennd5b -deficiency on lipid absorption in male and female mice (n=7-9 mice/genotype/sex). We observed significant, but relatively modest, reductions in lipid absorption efficiency in Dennd5b -/- mice in both sexes, despite a complete absence of plasma TAG after oil gavage. We hypothesized that this was due to metabolic utilization of TAG by enterocytes. Metabolic cage studies showed that both wildtype and Dennd5b -/- mice shift toward utilization of FAs when fed high-fat diet and Seahorse analysis revealed altered metabolic activity in Dennd5b -/- intestinal tissue. Electron microscopy (EM) revealed large electron dense structures that resemble autophagosomes in Dennd5b -/- enterocytes. Western blots detected altered Lc3 levels in Dennd5b -/- intestine, implicating autophagy. RNA sequencing of intestinal tissue detected changes in expression of genes involved in beta oxidation and EM imaging revealed altered mitochondrial morphology in Dennd5b -/- enterocytes. Conclusions: We conclude that autophagy contributes to degradation of unsecreted TAG in the Dennd5b -/- enterocytes, liberating free FAs which are utilized in mitochondrial oxidation. The sexually dimorphic effect of Dennd5b does not appear to be as prominent in mice as it is in humans. Overall, our findings demonstrate that Dennd5b plays a critical role in TAG secretion by intestinal tissue and that disruption of this process can impact systemic metabolism in both sexes.