Abstract
In 6-week feeding experiments with rats the behaviour of 20 oils and fats has been investigated, each of them being administered in 7 different dosages from 10 to a maximum of 73 Cal. %. The various oils and fats showed differences in growth-promoting effect. Nevertheless, the food-efficiency seemed to have a constant value and to be independent of the type of fat used. Only shea butter and palm oil were exceptions to this rule. As an explanation of the differences observed the presence of growth-inhibiting substances is suggested. Such substances need not be considered as harmful, but may possibly even exert a favourable influence, judging from the data on longevity.