Using intermittent fasting and a ketogenic diet to improve nutritional and clinical outcomes in long-stay, hospitalised canine spinal patients : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Manawatū, New Zealand

Abstract

A high prevalence of malnutrition occurs in human hospitals and has been associated with detrimental consequences. By comparison, very little is known in veterinary patients. Additionally, while underfeeding can lead to poorer outcomes, overfeeding hospital patients also causes negative effects, to the extent that purposeful caloric restriction has been touted as an ideal feeding regimen. Both caloric restriction and intermittent fasting (IF) have gained interest as therapeutic feeding regimens for several diseases, including neuronal injury.

The aim of this thesis was to explore hospital nutrition and IF in dogs. Firstly, the prevalence of malnutrition and body composition changes were determined in long- stay hospitalised patients. Results showed that most patients lost weight during hospitalisation, mainly from muscle. Additionally, body and muscle condition scoring did not accurately measure changes in composition, particularly in lean dogs. So predictive equations of body composition using morphometry in lean dogs were created. While feasible, it was discovered that breed-specific equations are needed, limiting its use.

Then, the metabolic and immunological effects of IF in healthy dogs were examined. Results showed that IF on a high-fat (HF) diet increased blood ketones and decreased leptin and ghrelin concentration. Also, a reduction in immunity occurred when the dogs were fasted after eating the low-fat diet, but not with the HF diet. Furthermore, ketone kinetics indicated that increasing the fasting duration from 24 to 48 hours caused highly variable responses amongst the dogs. Therefore, the beneficial effects of IF may be dependent on the individual. Finally, an IF regimen using a HF diet was applied in hospitalised dogs recovering from spinal injury. Results showed that the regimen was practical and reduced body weight loss. Also, higher fasted ketone concentrations were associated with shorter hospital durations in dogs that lost more weight.

In summary, long-stay hospitalised dogs lose a substantial amount of muscle. Also, a HF diet fed intermittently can increase ketone concentrations and may benefit patients with spinal cord injury. However, more work is needed to better understand what influences the variation in ketogenesis and utilisation in healthy and diseased dogs, and test the effects in a larger study population.