For the research, published in the journal Physiology & Behavior, scientists at Purdue studied the effect of just half a teaspoon of cayenne pepper on a group of 25 diners.I always find this kind of research interesting because, I believe, that if this is true then the reverse is true as well--i.e., eating some foods make you want to eat more.
While hot red pepper has been studied before as an appetite suppressant, this study was notable in that it compared people who liked spicy food with those who did not. At various times, diners were given a bowl of tomato soup laced with a half teaspoon of pepper, plain tomato soup, or plain tomato soup with a supplement of red pepper in pill form.
The effect was greater among diners who didn’t regularly consume spicy meals. Among that group, adding red pepper to the soup was associated with eating an average of 60 fewer calories at the next meal compared with when they ate plain soup. For both groups who ate red pepper in food, the spice also appeared to increase the metabolism and cause the body to burn an extra 10 calories on its own.
“We found that when individuals consumed the red pepper in the soup rather than the supplement, they burned more calories,” said Mary-Jon Ludy, who conducted the research as a student at Purdue and will join the faculty of Bowling Green State University. “There is something special about experiencing the burn from the red pepper.”
It's all about satisfaction.