Korean researchers fed five-week-old rats high-fat diets. Some got a daily oral injection of capsaicin, the fiery chemical in chile peppers, or just a control (the liquid that had been used to dilute the capsaicin). Throughout the course of the experiment, the rats getting capsaicin gained 8 percent less weight than untreated animals, and just a little more weight than rats eating a normal diet.
The capsaicin-treated rats also developed less body fat and accumulated smaller fat droplets within fat cells. The researchers noted “that capsaicin can have a significant inhibitory effect against fat accumulation.” But what's really significant in the research is the identification of which genes are selectively affected by consumption of dietary fat or by capsaicin.
They found, for instance, that a high fat diet up-regulated genes producing 17 proteins, including heat shock protein and preoxiredoxin. Some 10 of which were normalized or almost returned to normal in the animals treated with capsaicin. Some of the proteins altered by capsaicin treatment have been linked to obesity — or its prevention — before. Others appear to be newly identified players. A report of the new findings appears in the June 4, 2010 Journal of Proteome Research.
In total, the new findings suggest there may be dietary routes to slowing or even reversing obesity and related diseases through the use of pungent chemicals like capsaicin.