Breeding leaner sheep is a desirable goal provided reductions in fatness do not compromise survival and productivity, particularly in harsh environments. Whether some energy stores are more labile than others, the internal fat depots in particular, is not clear. Genetic variation in this trait could be usefully exploited in hill sheep where carcass fat is undesirable but energy reserves are important. Patterns of change in body energy stores need to be examined to determine when it is best to assess energy stores in animals. X-ray computer tomography (CT) provides a means to examine depletion and repletion of body energy but scans are not cheap. In order to use CT in a cost effective way, a number of variables need to be assessed from just a few scans. This report presents results of a study designed to define such a scanning approach in terms of which scans were most informative and which produced most accurate predictions of tissue size.