Correlation between Intermittent Fasting and Mental and Physical Fatigue in High‐fat‐induced Obese and Non‐obese Rats

Abstract

Intermittent fasting (IF) is an alternate pattern of eating and restricting food intake. This study evaluated mental and physical fatigue secondary to IF in high‐fat diet‐induced (HFD) obese male rats. Fifty‐four rats were randomly assigned to a HFD (n=28) or a standard diet (SD; n=26). After six weeks, the HFD rats were divided into one of four groups: obese HFD ad libitum (OB‐HFD‐AL), obese HFD intermittent fasting (OB‐HFD‐IF), obese SD ad libitium (OB‐SD‐AL), and obese SD IF (OB‐SD‐IF). Similarly, non‐obese controls were grouped into HFD ad libitum (C‐HFD‐AL), non‐obese HFD IF (C‐HFD‐IF), non‐obese SD ad libitum (C‐SD‐AL), and non‐obese SD IF (C‐SD‐IF). The IF groups fasted for 18 hours per day, seven days a week. After two weeks, their physical and mental fatigue was measured using open field (OF) and novel object recognition (NOR) paradigms. Regardless of the diet type, rats on IF gained weight at a slower pace (p< 0.05) and had lower glucose levels (p < 0.01) compared to the AL group. In non‐obese rats, ketone levels were higher in the IF‐HFD group compared to the IF‐SD (p<0.05) and AL‐SD (p<0.01) groups. Obese rats exhibited higher ketones in IF‐SD conditions versus AL‐SD rats (p<0.01). In both obese and non‐obese groups, AL‐HFD rats had higher ketone levels than AL‐SD rats (p<0.05). Increased ketone levels could be correlated with greater distance traveled during OF. IF protected against recognition memory deficit during NOR. Overall, this study demonstrates that increased ketone levels, whether caused by diet type or IF, correlate to decreased physical fatigue and protect against mental fatigue.