Cephalic postprandial thermogenesis in human subjects.

To study the role of food palatability on postprandial thermogenesis, a study was designed in which human subjects ingested palatable food while O2 consumption was measured continuously during 30 minutes before and 60 minutes after the meal. In a first experiment (normal feeding), the subjects ate a portion of sugar pie containing 1672 kJ. A rapid increase in O2 consumption was noted which reached a peak value at about 15 minutes from the beginning of the meal. In a second experiment (sham feeding), the subjects were given the same food and they were asked to chew it and to spit it out. During the first 30 minutes following the meal, sham feeding produced a significantly larger increase in O2 consumption than meal feeding, whereas in the second postprandial period the thermogenic effect of food was larger with meal feeding. The integrated elevation of O2 during one hour was the same with meal feeding as with sham feeding. These results show that sensory stimulations without food being absorbed caused an important increase in O2, and confirms in humans the presence of a cephalic postprandial thermogenesis. In the third experiment (blank feeding), the subjects mimicked the muscular activities associated with feeding such as hands, arms, jaw and throat movements. Blank feeding produced a small and transient increase in O2 consumption. An elevation of plasma norepinephrine was observed during the cephalic phase and this effect was significantly larger with sham than with meal feeding. Subjective ratings for palatability, hunger reduction and degree of fullness were higher with meal than with sham feeding.(ABSTRACT TRUNCATED AT 250 WORDS)