The present invention generally relates to increasing the efficiency of usage of an ingested exogenous biologically active substance by a body. In particular, the present invention relates to ways to improve the efficiency of utilization of ingested creatine in a body, in particular to increase the storage of creatine in the body. One embodiment of the present invention is the use of a combination comprising creatine and a soluble fiber for the preparation of a composition to increase the storage of creatine in the body.