Effects of Intermittent Fasting on Mental and Physical Fatigue in High Fat‐induced Obese and Non‐obese Male Rats

Abstract

Intermittent fasting (IF) is a dietary modification involving fasting for 16 to 18 hours per day while eating over the remaining 6- to 8-hour period. Intermittent fasting allows the body to use fat as the main energy source due to a decreased intake of glucose during the fasting period often promoting weight loss. Decreased blood glucose levels and cholesterol, increased sensitivity to insulin in those with diabetes and obesity are some of the benefits of IF. Furthermore, fasting diets have been related to cognitive benefits such as improvements in brain plasticity, learning, and memory. There is very little information on the physical and mental exhaustion related to IF and in particular cognitive behaviors while practicing IF. Whether IF offers benefits against physical and mental fatigue in addition to its effects on body weight, blood levels of glucose and ketones were tested in obese and non-obese rats in this study. Fifty-four male rats were randomly assigned to either a HFD (n=28) or a Standard Diet (SD) (n=26). After 6 weeks, the group receiving HFD gained significantly more weight compared to the SD group and therefore considered as the obese group and the animals receiving SD were now referred to as the non-obese group. These two groups were further subdivided into two groups each, one sub-group receiving food ad libitum and theother sub-group being placed on intermittent fasting. Animals in the IF groups were fasted for 18 hours a day, 7 days a week. After two weeks on these experimental diets, mental fatigue was measured using the novel object recognition test whereas physical fatigue was studied by measuring the distance traveled in the open field (OF) test. Regardless of diet type, rats on the IF eating pattern gained weight at a slower pace compared to those fed ad libitum (p< 0.0001), had lower blood glucose (p< 0.01) and exhibited a significant increase in ketone levels (p< 0.05). Regardless of the treatment group, distance traveled increased as ketone levels increased during OF. Similarly, animals with higher ketone levels interacted with the novel object more than those with lower ketone levels suggesting a lack of mental fatigue. In conclusion, IF, regardless of diet, is capable of inducing weight loss and better management of glucose levels. The weight loss and increased ketone levels experienced due to IF lead to greater physical and cognitive capabilities.