We are excited to announce a new publication! Hannah Godfrey and colleagues recently published their new article “Isoenergetic reduction of dietary macronutrients modulates respiratory quotients and heat increment of feeding but not energy expenditure in cats” in the Journal of Animal Science. Read on for a short summary of their research and findings below.
Objective
Our study aimed to investigate how different levels of dietary macronutrients—protein, fat, and carbohydrates—affect the metabolism of cats. Specifically, we looked at:
- Respiratory Quotients (RQ): This is the ratio of carbon dioxide produced to oxygen consumed, indicating which macronutrients are being metabolized for energy.
- Energy Expenditure (EE): This refers to the total amount of energy used by the body for basic metabolic functions.
- Heat Increment of Feeding (HIF): This represents the energy cost of digesting, absorbing, and metabolizing food.
Methods
We conducted a proof-of-principle study with 12 healthy adult male cats. Each cat was fed one of three diets: low-protein, low-fat, or low-carbohydrate, for two weeks in a Latin square design. We measured their metabolic responses using indirect calorimetry over a 22-hour period, focusing on RQ, EE, and HIF.
Findings
Our study revealed several key insights into how cats metabolize different macronutrients:
- Respiratory Quotient (RQ): Cats fed a low-carbohydrate diet showed lower RQ values compared to those on low-fat diets, indicating greater use of fats for energy. This suggests that cats can adapt their metabolism based on the macronutrient composition of their diet.
- Energy Expenditure (EE): Interestingly, the type of macronutrient did not significantly affect the overall energy expenditure. All cats showed increased EE after eating which was expected, but the differences between diets were minimal.
- Heat Increment of Feeding (HIF): The HIF, which represents the energy cost of digesting and absorbing food, was lower for cats on a low-protein diet compared to those on a low-fat diet over the entire post-feeding period. This indicates that dietary protein may have a higher metabolic cost compared to fat.
Conclusion
These findings challenge the notion that dietary macronutrient composition significantly impacts overall energy expenditure over a short period in cats. Instead, they highlight the adaptability of feline metabolism to different macronutrient levels, with a particular emphasis on the role of dietary fat in energy metabolism.
Summary of Findings
- Respiratory Quotient (RQ): Lower RQ values in cats on a low-carbohydrate diet suggest increased fat oxidation.
- Energy Expenditure (EE): No significant differences in EE between diets, indicating macronutrient composition does not directly affect EE.
- Heat Increment of Feeding (HIF): Lower HIF for low-protein diets compared to low-fat diets, suggesting higher metabolic cost for protein digestion.
- Adaptability: Cats can adjust their metabolism based on the macronutrient composition of their diet.
- Dietary Fat: Plays a crucial role in energy metabolism and should be carefully managed in cat diets.
Key Take-Aways
- Cats can efficiently metabolize different macronutrients, with dietary fat playing a significant role in energy metabolism.
- The type of macronutrient does not change overall energy expenditure.
- Lower carbohydrate diets may enhance fat oxidation in cats.
- Protein digestion has a higher metabolic cost compared to fat.
- Understanding macronutrient impacts can help in formulating balanced diets for cats.
Future Directions
Future research should explore the long-term effects of varying macronutrient levels on cat metabolism, particularly under different energy balance conditions. Investigating the role of specific types of fats and proteins, as well as their impact on mitochondrial function and oxidative capacity, could provide deeper insights into feline nutrition.
This research was funded by Champion Petfoods, NSERC, and Mitacs
Written by Hannah Godfrey, BScH, MSc, PhD Candidate
Reviewed by Dr. Adronie Verbrugghe, DVM, PhD, Dip ECVCN, Associate Professor and Royal Canin Veterinary Diets Endowed Chair in Canine and Feline Clinical Nutrition