The purpose of this study was to examine whether premature infants have higher rates of energy expenditure and diet-induced thermogenesis during intermittent feeding compared with continuous feeding. Using open-circuit respiratory calorimetry, we measured energy expenditure in 11 premature newborn infants on 2 successive days for 5 to 7 hours during and after either intermittent or continuous feeding. Infants were fed the same quantity of formula each day, either for 5 minutes or by continuous drip for 2 to 3 hours. The order of feeding type was randomized. No response of diet-induced thermogenesis to continuous feeding was found, whereas a peak increase of 15% over baseline was observed after intermittent feeding. Overall energy expenditure during the study period was significantly greater after intermittent compared with continuous feeding (2.18 +/- 0.07 kcal/kg per hour vs 2.09 +/- 0.05 kcal/kg per hour; p less than 0.05). Thus there was a mean 4% difference (range up to 17%) in energy expenditure between the two feeding modes. These results are similar to those obtained with adults and support the concept of the increased energy efficiency of continuous feeding. Further study will be necessary to document whether the increased energy efficiency provided by continuous feeding may be clinically significant.