Fifty-two children aged 6-46 months (mean 19 months), hospitalized for acute gastroenteritis (GE), were randomized after oral rehydration to receive 7 days of either traditional gradual refeeding (GR) or rapid refeeding (RR), the latter consisting of a full-strength lactose-limited diet, including lactase-treated whole milk. The study focused on the effect of a high energy intake, excluding possible negative effects of lactose. Both dietary regimens were well tolerated, the only difference in the clinical symptoms between the two regimens being a higher stool frequency within the RR group (p less than 0.02). The total energy intake, as well as energy derived from fat and protein, was significantly higher in the RR than in the GR group (p less than 0.0001). The mean daily energy intake of the latter group never reached recommended daily allowance (RDA) levels, while that of the RR group did on day 5. Moreover, during the whole period of dietary regimen, the RR group exceeded the RDA protein requirements (mean intake ranged 175-252%), while the GR group did not reach this RDA level until day 4. Milk was a major source of energy in the RR group, providing 47-59% of the daily energy intake. The short- and long-term weight gains in the RR group were only a little higher than those of the GR group, the difference being insignificant.(ABSTRACT TRUNCATED AT 250 WORDS)