Effect of meal size and frequency on postprandial thermogenesis in dogs

The influence of meal size and frequency on postprandial thermogenesis was studied in nine mongrel dogs (congruent to 18 kg). Oxygen uptake (VO2) and respiratory quotient (R) were continuously monitored by indirect calorimetry during the following experiments. In expt 1, four dogs were fed on alternated days either a large (3.1 MJ) or small meal (0.77 MJ). In expt 2, five different dogs were fed on alternated days either one large meal (3.1 MJ) or four consecutive small meals (0.77 MJ) spaced at 1.5-h intervals. In expt 3, the four dogs of expt 1 after being sham fed 3 times at 1.5-h intervals were given one large meal (3.1 MJ). The VO2 increase during the initial or cephalic phase (congruent to 50 min) was independent of the meal size but it was directly proportional to the amount of food ingested during the digestive phase. The total thermogenic response to four small meals (125 g) fed at 1.5-h intervals was twice as large as that of one large meal (500 g). One large meal (500 g) preceded by three periods of sham feeding was also found to be more thermogenic than a large meal only. For all experiments the changes in R were seen to parallel the postprandial fluctuations in VO2. These findings indicate that the enhanced heat production obtained when meal frequency is increased is caused by the repeated sensory stimulation produced by palatable food.