Comparison of the metabolic response to food in trained and untrained adults

Abstract

The resting metabolic response to a liquid test meal (Pillsbury Instant Breakfast, Pillsbury Co., MN) was determined in adult male and female Ss (24-59 yrs.). The trained Ss (N = 19) consisted of 15 men and 4 women who regularly ran an average of 35-40 mi/wk. The untrained Ss (N = 23) consisted of 13 men and 10 women who were members of the faculty and classified staff at UW-La Crosse. The experimental procedure consisted of hydrostatic weighing, ingestion of the test meal and preprandial and postprandial expired air collection. Resting metabolic rate (RMR) was determined from the latter two measurements, and the metabolic response to the meal (i.e., dietary-induced thermogenesis, or DIT) was the difference between pre- and postprandial RMR values. A t-test for independent groups was utilized for statistical analysis of the results. It was determined that DIT, when expressed in ml/kg/min., was significantly greater in the trained Ss than in the untrained Ss (p < .05). As hypothesized, there was no significant difference between the 2 groups when DIT was expressed per unit of lean body mass (i.e., in ml/kg LBM/min). It was concluded that the quantity of LBM could play a significant role in determining the metabolic response to food in adults. Further investigation of the capacity of skeletal muscle for thermogenesis is required to clarify the relationship between RMR and DIT.