The energy requirement for maintenance in pigs has been suggested to be a function of liveweight (W), using equations such as 0.46 MJ digestible energy (DE)/g W0.75 (ARC, 1981). For a 60 kg pig, the predicted energy required for maintenance can proportionately account for 0.30 of the daily energy intake. Therefore, substantial reductions in pig production costs could be achieved, if the energy required for maintenance was reduced. The present study estimated the energy required to maintain liveweight, rather than the energy required for maintenance, as the latter assumes no change in protein or lipid content of the animal. Genotypes from the Edinburgh lean growth selection experiment provided the experimental resource to determine if selection for lean food conversion ratio over seven generations had changed the DE required to maintain liveweight.