Protein meals and postprandial thermogenesis.

In North America the consumption of meat far exceeds that of fish. Because the palatability of the food has been shown to influence the thermogenic response to feeding, a study was designed to compare the metabolic response to 195-g beef steak and 250-g cod fillet containing both 43 g of proteins in a first experiment and to 250 g of both nutrients in a second experiment. The subjects who participated in this study gave a higher rating of palatability (obtained on a 10-cm visual analog scale) when the beef steak (7.4) was consumed compared to the cod fillet (3.0). Measurements of oxygen consumption during the cephalic phase (0 to 40 min) indicated a larger thermogenic response to the beef than to the fish meal. These findings suggest that the thermic response to feeding during the cephalic phase are related to the sensory stimulation of the meal. During the gastrointestinal phase (40 to >180 min) the response was not influenced by the type of food and was related instead to the amount of proteins ingested. Plasma amino acid determinations indicated differences between the beef and fish feeding. Plasma histidine and glutamine was higher after beef feeding. The meaning of these findings does not seem to be related at this time to the results obtained on postprandial thermogenesis. The increases in plasma insulin that were observed during both phases of feeding were similar for the beef and the fish meals. Despite a marked increase of insulin, plasma glucose remained unchanged after feeding either meals, suggesting an enhanced gluconeogenesis and an increased glucose utilization.