It makes sense to get multiple health benefits of fasting, just by looking at what happens when we do the opposite… when we overeat. Overeating (or eating unhealthy foods) causes obesity. Obesity is strongly associated with insulin resistance, high blood lipid levels, high blood pressure, lung and heart diseases, certain types of cancer, gallbladder, liver and digestive conditions, different forms of arthritis, kidney diseases and an overall decreased health span. The combination of obesity and autoimmune diseases is a very bad one [1].
Even if you are eating healthy and maintain your ideal weight, you can still benefit from fasting.Some of the best studies in humans are those conducted during Ramadam, when fasting is mandatory for adult Muslims. It is a one month fasting period (from sunrise to sunset). Other studies conducted in both animal and human studies support the many health benefits of incorporating fasting to your lifestyle.
General Health Benefits – Fasting Helps You Live Longer and Healthier
Research shows that fasting can increase overall health and longevity, while reducing neurological conditions, cancers and disorders of the circadian system. Fasting has anti-aging effects. Caloric restriction has been shown to increase lifespan in many animal models. In humans, caloric restriction slows down the aging process and delays the development of atherosclerosis, diabetes type 2, cancers and other conditions that would otherwise shorten the lifespan [2].
Fasting Improves the Metabolism of Sugar, Fats and Metabolic Syndrome
Periods of fasting decrease inflammation by reducing the production of pro-inflammatory molecules. Fasting improves body composition, modulating the visceral fat (the fat surrounding internal organs) and improves the levels of adipokines [3].
Adipokines are molecules produced by the fat tissues. Besides being involved in metabolism and appetite control, these molecules are also involved in immunity and inflammation, with a negative impact on those who have MS and/or are overweight [4].
Fasting and metabolic syndrome: Intermittent fasting (IF) can prevent and reverse all aspects of metabolic syndrome including abdominal fat, the inflammation, high blood pressure, reduced insulin sensitivity. IF helps improve nervous, neuromuscular and cardiovascular systems. IF protects the heart against ischemic injury ( including heart attacks), kidney and liver injuries, from studies in animal models. Fasting results in lower levels of insulin and leptin, while increasing the adiponectin and ghrelin, has a positive influence of gut microbiota (this protecting against metabolic syndrome) [5].
Fasting Relieves Symptoms of MS
One study evaluated the benefits of fasting for the month of Ramadam in 218 individuals with mild disability RRMS. The researchers found an increased quality of life (using both physical and mental markers of quality of life) of the participants [6]. A review of multiple studies evaluating the safety of one month fasting during Ramadam for those with MS found that calorie restriction can reduce inflammation and subsequent loss of myelin and attenuates disease severity [7]. Intermittent fasting is not only safe, but also reduces the severity of MS in animal models- if is started at an early phase of the disease [8].
Fasting mimicking diet reduced clinical severity in all subjects and completely reversed symptoms in 20% of subjects, according to another study conducted in animal models. The improvements were associated with an increase of the hormone corticosterone, T reg cells (which are beneficial for MS) and decreased pro inflammatory molecules TH1 and TH17 cells (which are linked with MS relapses). This diet was found to promote the regeneration of oligodendrocyte precursors (oligodendrocytes produce the myelin sheath). Similar to the chronic ketogenic diet, the fasting mimicking diet appears to be safe, feasible and potentially effective to treat RRMS, according to the authors of this study) [9].
Fasting Improves Mental Function, and Promotes Neurogenesis (the Formation of New Brain Cells), Fights Degeneration and Brain Inflammation
Whether you choose to fast or simply reduce the caloric intake it will work. In both cases, you will help your brain regenerate and work better. During caloric restriction and exercise, the electrical activity of the brain and the synapses between brain cells is increased. One study conducted in healthy fifty elderly participants showed that caloric restriction significantly improved mental performance. Improved brain function correlates with improved insulin resistance and low-grade inflammation, which are linked with cognitive decline [10]. (note: be aware that both inflammation and insulin resistance are found in MS, and contribute to the symptoms). Intermittent fasting and exercise increase neurogenesis via BDNF [11].
There are several pathways that are activated by intermittent fasting leading to decreased brain neurodegeneration and inflammation (see the technical section below). In a few words, intermittent fasting helps boost the antioxidant levels in the brain, as well as neurotrophic factors BDNF and FGF2, and reduce levels of proinflammatory molecules like TNFa, IL-1ß and IL-6 [12].
Fasting Has Anti- stress, Anti-anxiety and Anti-depression Effects
The anti-anxiety, anti-depression and anti-stress benefits of fasting are likely due to improved levels of various hormones and other chemicals with anti-depressant qualities (for example human growth hormone, thyroid hormones T3 and T4, insulin levels, ghrelin, orexin, ketone bodies, endorphins).
A study conducted in over 300 participants reveals that fasting can significantly improve stress levels and depression during Ramadam, when compared with the levels of stress and depression experienced before starting the one month fasting of Ramadam [13], [14], [15].
Alternate day fasting appears to be as effective as caloric restriction (calorie reduction by 25 -40%, while maintaining normal levels of protein, vitamins, minerals and water content). Both have antidepressant qualities, showing to relieve tension, anger and confusion while improving the sense of euphoria.
It appears that fasting fights depression by increasing the availability of neurotransmitters like serotonin and opioid like substances produced by in our body. Fasting (short-term, intermittent fasting) also increases norepinephrine levels [22].
Technical : the antidepressant effects of fasting are induced via orexin signaling activation. Orexin signaling is involved in consolidation of arousal, the regulation of metabolism, food intake and reward responses. Ghrelin levels (which also has antidepressant effects) also increase during caloric restriction. Fasting leads to a decrease of cerebral glucose, thus promoting neurogenesis, neurotrophin synthesis, neurotransmitter receptor expressions and the activation of BDNF. Fasting helps decrease the levels of leptin [15].
More details re: the molecular mechanisms and clinical applications of fasting : The role of nervous and endocrine systems in mediating the adaptive response of major organs to intermittent fasting (IF) : IF changes brain neurochemistry and the activity of neuronal network leading to improved brain function and peripheral energy metabolism, The brain regions involved in the adaptive response to IF are: 1. Hippocampus (responsible for cognitive processing), 2.striatum (involved in the control of the body movements), 3.hypothalamus (which controls the food intake and body temperature), and 4.brainstem (which controls cardiovascular system and digestion). IF improves the activity of the parasympathetic nervous system (key neurotransmitter :acetylcholine), leading to enhanced digestion : (improved gut motility and decreased inflammation), improved cardiovascular function (decreased heart rate and blood pressure, increased stress resistance). In the adipose tissue, IF will cause lipolysis, ketogenesis, decreased inflammation and increase adiponectin levels. In the liver and muscle cells, IF will promote increased insulin sensitivity, decreased IGF-1 levels. For more details see figure 2 of Dr Longo’s research study [12].
Regarding the neural circuits and cellular signaling pathways that mediate the adaptive response to IF : IF increases the activity of neurons in the hippocampus (which play a key role in learning and memory and often affected by brain degeneration, hippocampal demyelination is frequent and extensive in MS [16] ). The activation of these neurons will increase the production of BDNF, which promotes the growth and maintenance of the dendrites and synapses, and enhances the formation of new and healthy neurons from the neural stem cells. The protection against neurodegeneration also occurs via signaling pathways involving glutamate, BDNF, insulin and GLP-1. Insulin activates mTOR pathway thus increasing protein synthesis and cellular growth. For more details see Figure 4 from Dr Longo’s study [12].
Fasting Provides More Health Benefits than Ketogenic Diet
Ketogenic diet had been originally created to mimic fasting. It appears that the benefits of fasting and not limited to the ketogenic properties (the ability of using ketone bodies as form of energy instead of glucose). You can read my blog about the benefits of ketogenic diet here.
Fasting per se offers neuroprotective effects in animal models of neurodegenerative conditions like Parkinson’s, Alzheimer’s, stroke and Huntington’s disease. It looks that 40% lifelong calorie restriction helps against age related oxidative damage, while boosting antioxidant levels, decreases inflammatory markers like TNF-alpha and NF-kappa B. Calorie restriction protects the myelin and the oligodendrocytes (that produce myelin) and promotes mitochondrial function and overall healthy brain cells. Studies evaluating calorie restriction in animal models of MS found that restricting energy intake by 33% or 66% decrease severity disease and even protect against the development of disease. Another study confirms these effects of calorie restriction, further observing that this diet works through increasing the production of natural glucocorticoids, not through suppression of the immune system. Furthermore, the T cell function is improved by calorie restriction, while decreasing B cells and IFN gamma [17].
Fasting & Autophagy
Autophagy means literally “ self-eating”. Also, known as cellular cleansing, this mechanism basically leads to a true, deep cellular detox (way better than those green smoothies advertised for detox). Through autophagy, the body maintains a balance between manufacture of new ells components while breaking down dead, damaged or unnecessary proteins and other cell components. Autophagy is a normal physiological process characteristic to humans and other living organisms, which can be enhanced with fasting and other therapies. It offers our body protection against cancer, infections, neurodegeneration, controls inflammation and has a positive impact on the immune system function.
One well-recognized way of inducing autophagy is by food restriction. It was thought for a long time that calorie restriction can induce autophagy in many organs including liver, but not in the brain. However, we know now that short-term fasting has a profound impact on the brain cell’s autophagy. The process of neuronal autophagy was noted after 24 hours of foods restriction, with even more dramatic results at 48 hours.
On the other hand, chronic starvation can have the opposite effect on autophagy- you certainly don’t want that [18].
For more technical information, check out this study [19]. One of the key regulators of autophagy is mTOR. When mTOR is activated, it suppressed autophagy and the opposite is also true. This may explain why autophagy is more prominent in cortical neurons and Purkinje cells (which have reduced mTOR) [20].
Autophagy is turned off by glucose (insulin) and protein consumption. While consuming proteins and carbs would signal your body to go off fasting mode, I suspect that consuming fat alone (ie a teaspoon of coconut, MCT oil, or other pure fats) would not break the fast. I will have to do more research on this topic.
Cautions and Warnings
Fasting should be medically supervised. Even more important to seek medical attention if you have diabetes, as there is a risk of hypoglycemia, hyperglycemia after meals, diabetic ketoacidosis, dehydration and thrombosis. Recent evidence suggests that individuals with mild heart diseases, stable asthma, type 2 diabetes, and various digestive conditions can safely tolerate the one month fasting followed during Ramadam [17], [21].
Fasting should be used cautiously in cases of MS associated with Flammer syndrome [22]. The 24-48 hours fasting should be avoided, and rather use intermittent fasting with shorter periods of time without eating.
Common side effects of fasting include irritability and feeling hungry (especially during the first day of fasting), constipation, headaches, muscle cramps. These symptoms are rather signs of dehydration and depletion of certain electrolytes, thus they can be prevented by drinking more water. Even better, drink carbonated water or water with a little bit of salt added. Read my other tips on how to fast safely here.
