The Acute Effects of Consuming Capsaicin-rich Foods on Respiratory Quotient and Energy Expenditure in Healthy Adults: A Pilot Study

The public and healthcare providers wish to modify diets by incorporating healthy bioactive foods to manage weight and combat some of the negative consequences of obesity. Research suggests that food containing capsaicin, a bioactive ingredient in peppers, may be used as a tool for anti-obesity therapy through thermogenic effects, macronutrient increased fat/CHO oxidation ratio, negative energy balance, appetite regulation, and improved insulin sensitivity. The research objectives of this study are to determine acute changes in substrate oxidation and energy expenditure (EE) after consumption of a capsaicin-rich meal. The hypothesis of this study is that ingestion of a capsaicin-rich meal will result in a increase in fat oxidation and EE than from ingestion of a meal without capsaicin. We tested 10 adults (ages 21-42, BMI 21-33 kg/m^2) for two days using the Metabolic Cart to test their substrate oxidation and EE before and after consuming a standard meal for two hours. During the first test day, participants consumed a meal without capsaicin, and on the second test day they consumed the same meal except with an addition of 4tsp (8.20g) cayenne pepper containing 20.4mg capsaicin. Blood glucose, blood pressure, and anthropometric measurements were also monitored for all participants. There was no significant difference in baseline RMR and fasting blood glucose levels between the two test days. The respiratory quotient (RQ) was significantly lower (p-value 0.018) for the capsaicin test day, favoring fat oxidation. The average EE change over time was 19±8 kcal/2hr and 25±11 kcal/2hr for the non-capsaicin test day and capsaicin day respectively and was statistically significant (p-value: 0.000). The blood glucose control was not significant (p-value 0.538). The best estimate threshold level positively correlated with EE (p=0.024). The BP between the two test conditions was not significantly different. This study reports a lower RQ favoring fat oxidation and a higher EE after the consumption of a capsaicin-rich meal than without. More research needs to be done with a larger data set to present a significant outcome for blood glucose control.