Consumption of caloric and non-caloric versions of a soft drink differentially affects brain activation during tasting

Sensory-specific satiety, which is defined as a relative decrease in pleasantness, is increased by greater oro-sensory stimulation. Both sensory-specific satiety and pleasantness affect taste activation in the orbitofrontal cortex. In contrast, metabolic satiety, which results from energy intake, is expected to modulate taste activation in reward areas. The aim of this study was to determine the effects of the amount of oro-sensory stimulation and energy content on consumption-induced changes in taste activation. Ten men participated in a 2 × 2 randomized crossover study. Subjects were scanned twice using functional magnetic resonance imaging: after fasting for at least 2 h and after treatment, on four occasions. Treatment consisted of the ingestion of 450 mL of orangeade (sweetened with 10% sucrose or non-caloric sweeteners) at 150 mL/min, with either small (5 mL) or large (20 mL) sips. During scanning, subjects alternately tasted orangeade, milk and tomato juice and rated its pleasantness. Before and after the scans, subjects rated pleasantness, prospective consumption, desire to eat and sweetness for all tastants. Main findings were that, before treatment, the amygdala was activated more by non-caloric than by caloric orangeade. Caloric orangeade activated part of the striatum before, but not after treatment. We observed no main effects of sip size on taste activation and no interaction between sip size and caloric content. In conclusion, the brain responds differentially to caloric and non-caloric versions of a sweet drink and consumption of calories can modulate taste activation in the striatum. Further research is needed to confirm that the observed differences are due to caloric content and not to (subliminal) differences in the sensory profile. In addition, implications for the effectiveness of non-caloric sweeteners in decreasing energy intake need to be establishe