The inclusion of 8% mineral oil in a fat-free diet causes severe growth retardation in rats. In the present study, this growth retardation was found to be primarily due to the reduction in nutrient intake, but not to the exacerbation of essential fatty acid deficiency. In addition, the growth retardation caused by mineral oil ingestion was prevented by the concurrent inclusion of 10% water-insoluble dietary fiber [gobo fiber prepared from Arctium lappa L. (gobo in Japanese) or cotton cellulose powder] or 5% fatty acids (C12-C18) as well as glycerol monostearate. The prevention of growth retardation by these substances was due to their ability to inhibit mineral oil absorption from the intestinal lumen.