Intraperitoneal (IP) and intravenous (IV) milk fat inhibits leptin transport. Intraperitoneal (IP) and intravenous (IV) milk fat inhibits leptin transport. With IP injection, fat-free milk and intralipids were ineffective, whereas whole milk inhibited leptin transport. Milk given intravenously (0.2 ml milk administered intravenously with the I-Lep, with brain and serum samples collected 10 min later) was immediately effective in reducing I-Lep transport, whereas fat-free milk and intralipid were not. *P < 0.05; **P < 0.01. William A. Banks et al. Diabetes 2004;53:1253-1260 ©2004 by American Diabetes Association