UPDATE: I NO LONGER ENDORSE INTERMITTENT FASTING AS A WEIGHT LOSS TECHNIQUE. PLEASE SEE HERE.
We have already shown some of the interesting features of intermittent fasting. However, we are now trying to assess whether or not it may be beneficial for the long term health of your brain. Whether or not there may be a special fasting brain. With the incredible prevalence and destructive ability of neurodegenerative diseases it is important to look for methods and techniques that can promise an improved long term mental health deserves consideration. The problem with any potential fasting brain is that it is hard to test in humans due to the length of study that would be necessary. So we are going to need to look at studies done on other mammals, always remember these are not a perfect analogue, but still could give us a useful view into the fasting brain.
One of the most promising reviews of the potential for the fasting brain is this one, which shows several different mechanisms by which these changes may occur. I am going to take a moment here to attempt to detail them and explain how they might cause the desired neuroprotective effect.
- The first proposed mechanisms relies on a modification to the stress responses. Specifically the authors cite several studies that show increased levels of various protective proteins for both caloric restriction diets and for intermittent fasting. They further suggest that this increase in these proteins may contribute to the increased resistance to neurodegenerative stressors in these animals. Most importantly for our analysis of the fasting brain is that IF mice had a much greater survival than free-fed mice when they were injected with the stressor kainic acid was injected. This would seem to suggest there is some mechanism at play that increases the ability of the brain to handle these various stressors. However, it is important to remember that these effects may not be significantly different between intermittent fasting and normal caloric restriction.
- The second factor closely related to the reaction to the stressors is whether or not various neurotrophic factors, factors that help protect the brain are produced. Especially important here is their analysis of several studies that showed improved outcomes in mice with strokes, Parkinson’s, and Huntington’s. It appears at least one of these neurotrophic factors may aid in neurogenesis (creation of new neurons) in the hippocampus.
- The third one (and a topic we will be discussing in our next series of articles) is the increased creation and concentration of ketone bodies. In order to understand this one we need to pause for a moment and consider the nature of our body’s metabolism which I will simplify here purely for the sake of explaining this potential benefit. For our purpose’s we are going to divide the bodies metabolic pathways into two primary modes, either glucose or ketone. During normal glucose metabolism the body uses glucose, either consumed in the form or carbs, or that has been previously stored or converted from protein, as the primary energy source. In ketosis, which is the ketone burning mode, the body instead burns ketone bodies which are created in the liver from fatty acids. Namely, it is a fat-burning mode, insofar as the body is using fats now as the primary energy source. However, the reason this is truly important is that ketosis has already been shown to help in certain neurological disorders, especially seizure disorders. Moreover, fasting mice have a greater concentration of ketone bodies than normal calorie restricted mice. Suggesting that this mechanism might suggest that intermittent fasting provides a very direct and beneficial effect over normal calorie restriction. What’s even more important is the ketogenic diet has been tested in humans and it has been proved to help in childhood epilepsy and ketone bodies may even be able to help in Alzheimer’s disease. This seems to suggest that the observed increase in ketone bodies may bode well for the potential protective effect of intermittent fasting in humans.
- The next point is one closely related to a point I have already made in that intermittent fasting aids in improving insulin sensitivity. With the increasing evidence that Alzheimer’s disease seems to more and more be related to insulin sensitivity. For a reader friendly summary of this research check out one of my favorite websites: AlzScience. However, the important conclusion is that intermittent fasting improves insulin sensitivity greater than caloric restriction, and improved insulin sensitivity may help protect against Alzheimer’s disease.
- The next mechanism is again related to stress reaction, specifically compounds called cytokines. Cytokines are compounds that cause inflammation and thus mechanisms that decrease their prevalence are obviously important. The important conclusion to draw from this portion of the research is that a reduction in adipose tissue associated with an effective diet, can help prevent the rise of as many of these and therefore may help in the prevention of these neurodegenerative diseases.
- There are several other potential mechanisms proposed in this article, but they are quite speculative and reliant on a relatively deep understanding of biochemical pathways. Thus we will ignore them until there is more significant evidence that they may be truly contributing. The important conclusion is that there are several important mechanisms by which intermittent fasting and caloric restriction may benefit brain health.
There is still a question as to whether or not there may be benefits for the brain to fasting besides preventing neurological decline. There is some limited information that suggests there may be. This study done in mice seems to suggest that there were significantly improved cognitive functioning in fasting mice vs high fat diet mice. Again this is difficult to prove a connection to humans, but many fasters report feeling sharper after they begin fasting.
It will be a long time until we are sure that these results hold in humans, however, currently they represent an interesting concept for us to consider. Especially with the huge numbers of people affected by neurological disorders.