The University of Virginia’s Department of Anesthesiology performed an important study, led by Liaoliao Li, that examined intermittent fasting’s beneficial effects on the brain functions and structures in mice. Another leader in this study included Zhi Wang of the Department of Anesthesiology at the University of Virginia.
These scientists first began their study by stating the well-known fact that “obesity is a major health issue.” They then went on to expound on their statement by pointing out that obesity starting in the teen years has become another major concern in recent years.
Li and Wang persisted in examining the contrasting effects of obesity and intermittent fasting on both brain functions and structures before brain aging.
To come to a conclusion, 7-week old CD-1 wild-type male mice were subjected to either intermittent fasting (alternate-day), a high-fat diet (45% of the calories supplied by fat), or free access to a regular (controlled) diet for eleven months.
The mice exposed to intermittent fasting subsequently experienced improvement in learning and memory, which was assessed by the Barnes maze and fear conditioning (an explanation of what the Barnes maze and fear conditioning test is given below in the Notes), thicker CA1 pyramidal cell layers, higher expression of debrin (a dendritic protein), and lower oxidative stress compared to mice on the regular and controlled diet. In contrast, the mice fed with the high-fat diet became obese with hyperlipidemia.
Hyperlipidemia: “An excess of fats or lipids in the blood.”
Furthermore, these mice (the mice on the high-fat diet) experienced a “poorer exercise tolerance.” Also, the mice on the high-fat diet, unlike the mice who intermittent fasted, didn’t have any significant learning and/or memory impairments or improvements in brain structures as well as oxidative stress, compared to the mice on the regular diet.
Li and Wang concluded that “these results suggest that intermittent fasting improves brain functions and structures and that high-fat diet feeding started early in life does not cause significant changes in brain functions and structures in obese middle-aged animals.”
Note: What are CD-1 mice? “CD-1® mouse cells are isolated from CD-1® IGS mice purchased from Charles River. CD-1® IGS mice are outbred mice and are derived from a group of non-inbred Swiss albino mice developed at the Centre Anticancereux Romand in Lausanne, Switzerland. They were imported to the US in 1926 and to Charles River in 1959.” -sciencellonline.com
The two anesthesiologists began their introduction into their study by bringing attention to another fact that is well-known. One-third of adults and twenty percent of teenagers are obese in America (this statistic is from 2013). They go on to say that a “high-fat diet has been considered a significant contributing factor for the pandemic of obesity in the U.S.A. It is known that obesity and its associated metabolic disturbance including hyperlipidemia have been identified as risk factors for cardiovascular diseases, diabetes, and many other diseases. However, little is known about the effects of obesity on brain functions and structures.”
In the introduction, these two main questions were indirectly and directly asked: How does intermittent fasting affect cognitive functions and brain structures in mice? And, how significant of a difference does intermittent fasting have compared to mice on regular and high-fat diets?
Now, it is important to note that the experiment was conducted on younger mice so as to examine the results before variables like “obvious aging-related process has started.”
The experiment was done over a period of eleven months. “Their learning, memory, and brain biochemical and structural changes were determined. We focused on measuring brain oxidative tree indices because oxidative stress is known to induce cell injury and impairment of cognitive function.”
This study was conducted in such a way that it would simulate human teenager obesity that continues to be in effect until adulthood. Also, in the study, the protective effects of intermittent fasting on the brain when influenced by obesity were examined. A maze, known as the “Barnes maze” and a “fear conditioning course” were “tools” used to test the mice’s consequential reaction under stress-induced situations.
There were two groups of 15 mice and one of 19 mice that were subjected to either the controlled (regular diet), intermittent fasting, or high-fat diet feeding group. Each cage contained 3-4 mice. At the end of the eleven month feeding period, 15 mice were left in each group.
Originally, 19 mice were in the intermittent fasting group, but 4 eventually died. Thus, making the number of survivors in each group 15.
What were the reasons for these 4 deaths? The researchers answered this question by stating, “There were no significant mortality rates among the three groups. The 4 mice that died in the intermittent fasting group were the lightest among their cage-mates from the beginning of the feeding protocol until their death.”
The researchers found the results of this study to be groundbreaking!
For part 2 of The Improvement Pill (the results of this study) click here: Brain Improvement Pill (Part 2)
-Why was the Study conducted on Young Mice?
It is a vital observation to make that the decision by these researchers–as expressed numerous times throughout the study–was to choose this specific protocol to study the effects of long-term obesity (when starting in the teen years) on the learning, memory, and brain structures of middle-aged mice. The research into this subject has become very critical given the rapidly growing amount of teenagers suffering from obesity. “The negative findings in our study suggest that significantly harmful effects on the brain have not occurred yet in the obese middle-aged mice. However, the effects of long-term obesity on aging-related brain changes are not clear yet. Future studies are needed to address this issue by using obese elderly animals.” In contrast to these little to no changes in the brains of the mice with the high-fat diet, the findings for the mice that attempted intermittent fasting suggested that intermittent fasting prompted beneficial changes in the brains of mice. The keynote from this research was that improvement was made in hippocampus-related learning and memory in the mice that underwent intermittent fasting. The researchers noted this when it was shown that the performance in the “context-related learning and memory in the fear conditioning test was better than control mice.”
-What was the Barnes Maze?
The Barnes maze was a test designed to evaluate the spatial learning and memory improvements and diminishment in the mice after the 11 month feeding period. The mice were put in the middle of a round platform with twenty holes that were equally spaced. One of these holes was connected to a larger chamber which was known as the “target box.” The mice were prompted to enter the box. This was conducted by using loud noises (85dB) and bright lights (200W) on the platform of the boxes. “Mice went through a spatial acquisition phase that took four days with four trials per day and fifteen minutes between each trial. Mice then went through the reference memory phase to test the short-term retention on day five and long-term retention on day twelve. The latency to get into the box each day was recorded.”
-What was the Fear Conditioning Test?
Shortly after the Barnes maze, approximately one week after, the mice were forced to experience the fear condition test. Essentially, mice were established in their own test chamber and then wiped with 70% alcohol and sent through 3 tone-foot shock pairings (tone: 2000Hz, 90dB, the 30s; footshock: .7mA, 2s). Additionally, the mice experienced an interval of one minute in the dark. The mice were eventually taken out of the chamber when the experiment and/or test was finished. Mice were not placed back into the chamber until 24-hours later. This time they were placed in the chamber for six minutes and with the absence of both time and shock. It was recorded how much time the mice had a “freezing behavior” in a six-second interval. “Mice were placed two hours later in a test chamber that had different context and smells from the first chamber (this second chamber was wiped with 1% acetic acid). Freezing was recorded for three minutes without the auditory conditioning stimulus. The auditory stimulus than was turned on for three cycles, each cycle for thirty seconds followed by a 1-minute interval (4/5 minutes total). The freezing behavior in the 4.5 minutes was recorded.”
- Li, Liaoliao, and et al. “(PDF) Chronic Intermittent Fasting Improves Cognitive Functions and Brain Structures in Mice.” ResearchGate, 3 June 2013,