Comparison of intermittent fasting and voluntary wheel running on physical and cognitive abilities in high-fat diet-induced obese rats.

Regular physical activity is a proven routine for weight management in addressing obesity. Another method that has gained attention for its health benefits is intermittent fasting (IF). Physical and cognitive abilities while on these routines are poorly understood in the obese population. Sixty-five male Sprague Dawley rats at 7 weeks of age were subjected to diet-induced obesity by feeding a high-fat diet (HFD) or a standard diet (SD) for 8 weeks, after which behavioral testing was performed to detect any changes in physical and cognitive abilities. Rats from the HFD-fed (now considered obese) and SD-fed groups were then subjected to IF (18-hour fast and 6-hour feeding daily), voluntary wheel running (VWR), or control conditions for 3 weeks before repeating the same behavioral testing protocol. IF resulted in less weight gain (p<0.05) and elevated ketone levels (p<0.05) in both SD and HFD-fed groups. IF improved physical activity when compared to VWR and control animals in both SD and HFD-fed groups (p<0.05) while the VWR group in the SD-fed rats exhibited less physical fatigue compared to IF and controls (p<0.05). Additionally, elevated ketone levels were weakly correlated with decreased physical (p<0.0001) and exploratory behavior (p<0.01). These results suggest that IF is more effective than VWR in HFD and SD-fed rats in minimizing weight gain and retaining physical activity, and ketones may play a part in establishing the reported physical benefits. Exploration of physiological mechanisms between ketones, diet, and exercise will help fight obesity and many associated diseases.

Intermittent fasting and mental and physical fatigue in obese and non-obese rats.

Intermittent fasting (IF) is an alternating pattern of restricting eating. This study evaluated mental and physical fatigue secondary to IF (daily 18-hour fast, 7-days-a-week) in the high-fat diet (HFD)-induced male obese Sprague Dawley 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-IF (OB-HFD-IF), obese SD-AL (OB-SD-AL), and obese SD-IF (OB-SD-IF). Similarly, non-obese controls were grouped into HFD-AL (C-HFD-AL), non-obese HFD-IF (C-HFD-IF), non-obese SD-AL (C-SD-AL), and non-obese SD-IF (C-SD-IF). After 2 weeks of IF, mental and physical fatigue were measured using open field (OF) and novel object recognition (NOR) tests. 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 than IF-SD (p<0.05) and AL-SD (p<0.01) animals. Obese rats exhibited elevated blood ketone levels in IF-SD conditions versus AL-SD rats (p<0.01). AL-HFD rats had higher ketone levels than AL-SD animals in both obese and non-obese groups (p<0.05). In conclusion, rats with higher blood ketone levels, whether they were on IF or AL, traveled a greater distance during OF suggesting a lack of physical fatigue. There was no significant difference between IF and AL during NOR indicating a lack of mental fatigue. Thus, IF results in reduced body weight and blood glucose levels but does not induce physical or mental fatigue.

Correlation between ketones and mental fatigue in high fat-induced obese and non-obese rats.

Obesity, often caused by a diet high in calories and low physical activity, may induce physical fatigue, as experienced via decreased locomotor activity and mental fatigue such as impaired cognition. This study aims to evaluate glucose and ketone levels secondary to high-fat diet (HFD) exposure and signs of physical and mental fatigue. Fifty-four 7-week-old male Sprague Dawley rats (Rattus norvegicus) were assigned to either an HFD (n = 28) or a standard diet (SD; n = 26) for a 6-week period during which body weight, blood glucose, and ketones were measured twice per week. An open field (OF) paradigm was used to measure locomotor activity, while novel object recognition (NOR) test was used as an indicator of cognition. Animals in the HFD group weighed more than SD rats (8.4 g; p < 0.05) starting at Day 11, blood glucose levels were higher in the HFD group versus SD rats (3.9 mg/dl; p < 0.05) beginning in Week 5, and ketones were lower for the HFD versus the SD group throughout the study (0.34 mmol/L on average; p < 0.05). Although there was no significant difference in locomotor activity between the HFD and SD groups (p = 0.12), regardless of diet, higher ketone levels were associated with increased NOR time and ratio between the familiar and novel objects (p < 0.01). Thus, this study provides evidence that an increased level of ketones is associated with greater cognitive performance and a lesser probability of experiencing mental fatigue.