Sustaining energy with high fat diets
Dr Mark Roberts, PhD
Dogs can source energy via all three of the macronutrients (protein, fat and carbohydrates). However, each of these provides energy differently, and can impact the animal regarding how sustained energy is over the duration of a day. The most common format used in dog food involves the extrusion process, producing kibble. These diets need a significant amount of carbohydrate content, vital for the forming of dough, required for extrusion to occur. As the dominate macronutrient in these diets, dogs consequently use a significant amount of it for energy. When a dog consumes carbohydrates, they are broken down to form glucose, providing the most rapid supply of energy. The downside with this process is that glucose also has the smallest amount of storage in a dog’s body, mainly in muscle1, in the form of glycogen. A high carbohydrate diet, especially one that is processed, results in an increase in glucose levels, referred to as a “glucose spike.” To bring these levels down, insulin is released from the pancreas2. This leads to a dog having a surge of energy, followed by feeling tired and depleted. Additionally, for a dog that is active, the limited storage capacity of carbohydrates (or glycogen), means depletion will eventually occur3. At this point, a dog will become fatigued, unless more carbohydrates are consumed.
Another macronutrient, which unexpectedly can also be utilised as a source of energy by a dog, is protein. This is accomplished via the formation of glucose from non-carbohydrate sources using metabolic pathways4. Certain amino acids (which make up protein) are used for this process to occur, with serine and alanine5 key providers. However, the use of protein as an energy source is not beneficial, due to the macronutrient serving many important roles, such as enabling chemical messengers and important reactions to occur. Moreover, breaking down protein from muscles is obviously not an ideal approach for the health of a dog. Concentrating on other sources of energy a dog can use, is therefore more advantageous.
The remaining macronutrient is fat, being significantly more energy dense than both protein and carbohydrates, with a gram of fat producing 8.5 kcals, compared to 3.5 kcals both from protein and carbohydrate. Fat can of course be accessed from a diet, with bodyfat also serving as an additional source of energy. This is evident, in that even a very lean dog has fat stores containing thousands of kcals of energy. With fat as the primarily energy source for a dog, both fatty acids and glycerol concentrations increase (from the breaking down of triglycerides). When this occurs, a significant reduction in the use of stored carbohydrate (glycogen) in dogs is evident6. By having glycogen stores that are better stabilised is of value, reducing the potential of “running out,” of a rapid source of energy if required. Another process which results from the breaking down of fat by a dog, is a change to using non carbohydrate sources for energy (fat) from carbohydrates7.
This shift to using fat instead of glucose for energy, also produces ketones, or ketone bodies, providing an alternative fuel source to glucose for cells in various organs and tissues, including the brain8. From the standpoint of the interaction between glucose and insulin, the difference between carbohydrates being the dominant fuel source to fat is substantial. The increase in glucose and insulin concentrations, linked with high carbohydrate fed dogs does not occur in animals after consuming a high fat, low carbohydrate diet. Moreover, no meaningful change in values are evident from a fasted state. Consequently, this eliminates the highs and lows of energy, frequently observed in high carbohydrate diet fed dogs.
In conclusion, a high fat, moderate protein diet, with no, or a very minimal inclusion of carbohydrate content is the optimal approach to provide a dog with sustained energy. This, not only, provides over twice as much energy to a dog, compared to protein and carbohydrates, but delivers this, on a constant basis. Furthermore, it reduces the rate of running out of stored carbohydrate in the animal, much more so, than if carbohydrates are the main source of energy.
References
1. Brännback, E. (2020). The effect of two diets with different carbohydrate content on glucose markers in dogs. Animal Nutrition.
2. Nguyen, P., Dumon, H., Buttin, P., Martin, L., & Gouro, A. S. (1994). Composition of meal influences changes in postprandial incremental glucose and insulin in healthy dogs. The Journal of nutrition, 124, 2707S-2711S.
3. Reynolds, A. J., Fuhrer, Laurent., Dunlap, H. L., Finke, Mark., & Kallfelz, F. A. (1995). Effect of diet and training on muscle glycogen storage and utilization in sled dogs. Journal of applied physiology, 79(5), 1601-1607.
4. Belo, P. S., Romsos, D. R., & Leveille, G. A. (1977). Influence of diet on lactate, alanine and serine turnover and incorporation into glucose in the dog. The Journal of Nutrition, 107(3), 397-403.
5. Kuttner, R. E., & Spitzer, J. J. (1978). Gluconeogenesis from alanine in endotoxin-treated dogs. Journal of Surgical Research, 25(2), 166-173.
6. Shulman, G. I., Lacy, W. W., Liljenquist, J. E., Keller, U., Williams, P. E., & Cherrington, A. D. (1980). Effect of glucose, independent of changes in insulin and glucagon secretion, on alanine metabolism in the conscious dog. The Journal of Clinical Investigation, 65(2), 496-505.
7. Chu, C. A., Sherck, S. M., Igawa, K., Sindelar, D. K., Neal, D. W., Emshwiller, M., & Cherrington, A. D. (2002). Effects of free fatty acids on hepatic glycogenolysis and gluconeogenesis in conscious dogs. American Journal of Physiology-Endocrinology and Metabolism, 282(2), E402-E411.
8. Vendramini, T. H., Amaral, A. R., Rentas, M. F., Nogueira, J. P. D. S., Pedrinelli, V., de Oliveira, V. V., … & Brunetto, M. A. (2024). Ketogenic diets: A systematic review of current scientific evidence and possible applicability in dogs and cats. Journal of Animal Physiology and Animal Nutrition, 108(2), 541-556.
