Skoog's lizards (family Cordylidae) live on and in the slipfaces of shifting sand-dunes in the hyperarid Namib Desert. We measured field metabolic rate (FMR) and water flux (doubly labelled water), diet (stomach content analysis), chemical composition of food items (water, energy and mineral contents), evaporative water loss in the field, and standard metabolic rate (SMR) in the laboratory. These lizards had FMRs and food requirements that are about half those of other lizards, although their SMR was not notably low. Water intake rates in the field were high due to consumption of very succulent growing shoots of nara, a perennial shrub in the cucumber family that stays green all year round on underground water obtained via a long tap-root. Consumption of wind-blown, dry plant material (detritus, comprising about 20% of the dry matter in the average diet) may be related to mineral nutrition. Behavioural adaptations (reduced above-ground activity, which lowers food and energy requirements, and selection of succulent plant food) rather than physiological adaptations that reduce resource requirements, appear to be most important in permitting survival of this lizard in its bleak habitat.