Caseinomacropeptide (CMP) is a glycopeptide of 64 amino acid residues derived from the C-terminal of mammalian milk K-casein. Recently, human CMP (hCMP) was produced from the recombinant yeast Saccharomyces cerevisiae. In this study, the antiobesity activity of the recombinant hCMP (rhCMP) was investigated in vivo using Sprague-Dawley rats. The rhCMP did not affect the rats fed with a normal fat diet (fat content, $5.0\%$), but decreased the body weight gain of the rats fed with a high fat diet (fat content, $20\%$) by up to $19\%$. Autopsies revealed that the weights of the liver, kidney and adipose tissues decreased when the rats were given the rhCMP, which also reduced the lipid concentrations in the plasma and liver, but enhanced the fecal excretion of lipids. These results suggest that rhCMP prevent the accumulation of lipid by stimulating its fecal excretion, so could be used as a food supplement to alleviate the obesity problem caused by a high fat diet.