In a series of human studies, Yoshioka et al16-19 showed an increase in
diet-induced thermogenesis and a decrease in respiratory
quotient immediately after a meal to which red pepper
(capsaicin) was added. This finding implies a shift in substrate
oxidation from carbohydrate to fat oxidation. This increase in
the facultative phase of diet-induced thermogenesis was
probably due to beta-adrenergic stimulation.16 They also
showed a decreased appetite, decreased cumulative food
intake18 and increased energy expenditure17,19 after con-
sumption of red pepper. In those studies by Yoshioka,
capsaicin was given orally as red pepper. Therefore, the
reducing effect on energy intake could be due to the sensory
effect of capsaicin or the postingestive, gastrointestinal effect.
We assessed the sensory and gastrointestinal contributions to
the possible satiety effect of capsaicin by offering the same
dosage of capsaicin in tomato juice (sensory and gastrointest-
inal exposure) or in capsules (gastrointestinal exposure) that
were swallowed with tomato juice.