Did you eat breakfast today? How about last night? Probably you had dinner too? Great! As a nutritionist I am always ready to tell you not to skip meals. Lately, however, I’ve been considering just the opposite. I’m talking about deliberately avoiding food through fasting. This ancient practice has been revered for ages as a health and spiritual tool. In the time of Hippocrates, fasting was prescribed to treat all manner diseases and religions have used it to help man open up to spiritual experiences. But isn’t this counterintuitive? Haven’t you experienced that slow, foggy mental state that accompanies skipping a meal? As a clever candy bar commercial suggests: you’re not you when you’re hungry. I know I’m not me when I haven’t eaten but the mental effects of longer bouts of fasting may surprise you.
So what are the mental effects of fasting? Clinicians have reported finding improvements in mood, mental clarity, vigilance, a sense of improved well-being, and sometimes euphoria.
But first, what exactly is fasting?
Fasting can refer to many practices but in the scientific literature there are 3 main types of fasting:
- Intermittent Fasting (IF): Also known as alternate day fasting, this is the practice of abstaining from food every other day for a period of time. More on the effects of this type of fasting in Ann’s post later this week!
- Therapeutic Fasting: This is the continuous restriction of food for a period of 2 days to a few weeks consuming only 200-500 calories per day in the form of fruit or easily digested carbohydrates like rice.
- Calorie Restriction: This process involves consuming 30-40% less calories than usual everyday for an extended period of time.
Short Term Effects: Moods and Migraines
It is stressful to go without food but this is not an uncommon occurrence. The mood-boosting effects of fasting may be an evolutionary adaptive mechanism for periods of famine. In other words, when food is scarce our bodies release chemicals to help protect our brains from the negative effects. These chemicals can put us in a good mood–but, as you know if you have skipped a meal or two, it takes a few days. During the first week of fasting, the body begins to adapt to starvation by releasing massive amounts of catecholamines including epinephrine (adrenaline), norepinephrine, and dopamine as well as gluco-corticoids, steroid hormones involved in regulating the immune response and glucose metabolism. All of these chemicals are also released during the infamous ‘fight or flight’ response. After a while, our body responds to this stress through a boost of feel-good and protective chemicals.
A study by Michaelson et. al. in 2009 showed that therapeutic fasting alleviates depression symptoms and improves anxiety scores in 80% of chronic pain patients after just a few days. The mechanism behind this is not known but it might be linked to the release of endorphins in the first 48 hours of fasting. Similar to a runner’s high, endorphins, which resemble opiate drugs, make you feel good in response to a metabolically stressful event. Another study by Michaelson et. al. in 2003 has demonstrated that after 8 days of therapeutic fasting, sleep improves significantly compared to pre-fasting conditions. Anyone who has ever had a few nights of poor sleep knows this can be a powerful moderator of mood as well as changing your general sense of well-being, which was also subjectively reported to improve with fasting.
Other researchers have found that fasting boosts the levels of available serotonin in the brain. This is thought to explain the interesting findings that therapeutic fasting can significantly reduce migraine headaches. Currently, therapeutic fasting is not a common practice for such disorders in the United States but older studies suggest that this is efficacious.
Fasting in the Aging Population
In older populations the decline of mental functioning and the increased risk for neurodegenerative disorders such as Alzheimer’s and Parkinsons become a larger concern. Recent research suggests that fasting may mitigate the development of these situations.
Reducing Food to Reduce Neurodegenerative Disorders
Although I have yet to find conclusive studies of actual humans who fast regularly experiencing better mental acuity and reduced risk for degenerative diseases, at least in rodents the evidence is fairly solid. Intermitent fasting increases the chemical known as BDNF (brain-derived neurotrophic factor), which is associated with increased hippocampal neurogenesis. That means, the more BDNF you make the more likely it is that your brain is building new neurons. In animal models, this chemical improves the functional outcome in situations of stroke, Parkinson’s disease, and Huntington’s disease.
Similarly, the large amounts of ketones produced through restricted feeding, to feed the brain in replacement of the glucose it would rather have, are also protective against neurodegenerative diseases in rodent models.
The brain also responds to short-term fasting through autophagy. Autophagy is an important process by which the body’s cells break down old structures and waste materials for recycling into new materials. Through this process, toxins are been removed from the neuronal cells. Recent research by Alirezaei et. al. have shown that autophagy increases in mice after short-term food restriction. This is an important link to neurodegenerative diseases. Lower levels of autophagy are associated with increased neurodegeneration so this suggests that increasing autophagy through fasting might slow the development of neurodegenerative disorders.
Preservation of Mental Ability
Even in the absence of neurodegenerative disorders, mental ability declines with age. However, IF has been demonstrated to improve the mental functioning of aging animals. A study by Singh et. al. demonstrated that age-related decline in cognitive and motor abilities could be ameliorated through fasting. IF delayed the onset of decline in motor skills and spatial memory as well as decreased markers of oxidative stress and mitochondrial dysfunction. As a result, the fasting rats had better balance and could learn skilled behavior faster than rats fed as much as they wanted. Surprisingly, fasting restored the mental capacity through increased neurogenesis and increased density of neruonal synapses.
The effects of fasting are wide-ranging and most of what we know about how it changes our brains is from research on rodents. However, it is clear that fasting can change brain chemistry, mood, and mental functioning to the point of reducing risk for neurodegenerative disorders. This doesn’t mean that we should all begin a regimen of fasting but I have taken from this research a new appreciation for the power of our bodies to adapt to how we live in unexpected ways. Although fasting is generally regarded as a safe practice, it should not be done with out careful consideration. Have you ever tried fasting and felt a change in mental state?