Hedgehog (Hh) signaling plays an important role in embryonic development of many tissues, including the gastrointestinal tract. Sonic Hh-and Indian Hh-deficient mice die before or soon after birth, precluding further study of this signaling pathway in the mature intestine. Maternal transfer of inactivating monoclonal antibodies to Hh proteins (anti-Hh moAb) during late stages of embryogenesis or to early postnatal mice produced intestinal villous abnormalities, progressive runting, and severe malabsorption of dietary fat. In the present study, we sought to determine the effect of inhibiting Hh signaling on weight gain and lipid absorption in adult mice. Anti-Hh moAb was administered to adult Balb/c mice fed either a low-fat, nonpurified diet or a high-fat, semipurified diet, and to adult ob/ob mice fed the low-fat, nonpurified diet. Weight gain was significantly inhibited by anti-Hh moAb treatment in Balb/C mice fed the high-fat, but not the low-fat diet and in ob/ob mice. Further analysis of adult Balb/c mice fed the high-fat diet demonstrated that although total lipid absorption was normal, the rate of triglyceride absorption was significantly delayed in mice treated with anti-Hh moAb and they had significantly increased fecal FFA excretion. Hepatic steatosis, found in high-fat fed Balb/c mice treated with the control moAb, was abrogated by anti-Hh moAb administration. These findings point to a potential role for Hh signaling pathways in diet-induced abnormalities of lipid metabolism.