Postprandial energy expenditure and respiratory quotient during early and late pregnancy.

Rates of energy expenditure after a 750-kcal meal were determined by open circuit, indirect calorimetry for four women in late pregnancy (30 to 40 wk gestation), six women in early pregnancy (10 to 20 wk gestation), and six nonpregnant women. Preprandial resting metabolic rates, expressed in kcal min-1, were 22.5% higher (p less than 0.05) in the late pregnancy group compared to the early pregnancy, and 15.9% higher (p less than 0.05) in the early pregnancy compared to the nonpregnant women. No differences in preprandial energy expenditure rates were seen between groups when expressed as kcal kg-1 h-1. Rates of energy expenditure increased above preprandial levels in all groups by 15 min postprandially and remained significantly elevated for the next 175 min. The total increase in postprandial energy expenditure above preprandial levels did not differ significantly due to stage of gestation. Respiratory quotient, the ratio of VCO2:VO2, increased significantly in all groups (p less than 0.05) above preprandial levels by 15 min after the meal. Respiratory quotient values began decreasing after 95 min and returned, in all groups, to preprandial levels by 175 min. The results from this study demonstrate that the increase in the rates of energy expenditure after a mixed meal was not altered by gestation.