Intermittent fasting has become a popular approach to help people lose weight. It has also been touted as a way to reboot metabolism, control chronic disease, slow the aging process, and improve overall health.
Intermittent fasting produces effects on the functioning of the brain PHOTO archive The Truth
Meanwhile, some research suggests that intermittent fasting may provide a different way for the brain to access energy and offer protection against neurodegenerative diseases such as Alzheimer's disease, writes sciencealert.com.
This is not a new idea – the ancient Greeks believed that fasting improves thinking. But what does the evidence say today?
What is intermittent fasting?
Our diet—including the calories we eat, our macronutrient composition (the ratio of fat, protein, and carbohydrates we eat) and the timing of our meals—are lifestyle factors we can change.
People do this for cultural reasons, for weight loss, or for possible health gains.
Intermittent fasting consists of short periods of calorie restriction in which food intake is restricted for 12 to 48 hours (usually 12 to 16 hours per day), followed by periods of normal food intake. The intermittent component means a recurrence of the pattern instead of a post “unique“.
Deprivation of food for more than 24 hours typically constitutes starvation. This is distinct from fast to fast due to specific biochemical changes and nutrient deficiencies that can be potentially harmful if continued for long periods.
Four ways fasting works and how it might affect the brain
The brain accounts for approximately 20% of the body's energy consumption. Here are four ways intermittent fasting can act on the body that may help explain its potential effects on the brain.
1. Ketosis
The goal of many intermittent fasting routines is to flip a “metabolic switch” to switch from burning predominantly carbohydrates to burning fat. This is called ketosis and usually occurs after 12-16 hours of fasting, when the liver's glycogen stores are depleted. Ketones—chemicals produced by this metabolic process—become the brain's preferred source of energy.
Because it is a slower metabolic process to produce energy and for its potential to lower blood sugar levels, ketosis can cause symptoms of hunger, fatigue, nausea, low mood, irritability, constipation, headaches, and mental “fog”.
At the same time, as glucose metabolism in the brain declines with age, studies have shown that ketones may provide an alternative source of energy to preserve brain function and prevent age-related neurodegenerative disorders and cognitive decline.
Consistent with this, increasing ketones through supplementation or diet improves cognition in adults with mild cognitive impairment and those at risk of Alzheimer's disease.
2. Circadian synchronization
Eating at times that don't match our body's natural daily rhythms can disrupt the way our organs work. Studies of shift workers have suggested that it may also make us more prone to chronic diseases.
Time-restricted eating is when you eat your meals within a six to ten hour window during the day when you are most active. Time-restricted eating causes changes in gene expression in tissues and helps the body during rest and activity.
A 2021 study of 883 adults in Italy indicated that those who restricted their food intake to ten hours a day were less likely to have cognitive impairment compared to those who ate without time restrictions.
3. Mitochondria
Intermittent fasting could provide brain protection by improving mitochondrial function, metabolism and reducing oxidants.
The main role of mitochondria is to produce energy and they are crucial for brain health. Many age-related diseases are closely related to an imbalance between energy demand and supply, likely attributable to mitochondrial dysfunction during aging.
Studies in mice suggest that alternate-day fasting or cutting calories by up to 40% could protect or improve brain mitochondrial function. But not all studies support this theory.
4. The gut-brain axis
The gut and brain communicate with each other through the body's nervous systems. The brain can influence how the gut feels (think “butterflies” in the stomach when you're nervous), and the gut can affect mood, cognition, and mental health.
In mice, intermittent fasting has shown promise for improving brain health by increasing the survival and formation of neurons (nerve cells) in the brain region called the hippocampus, which is involved in memory, learning and emotion.
There is no clear evidence of the effects of intermittent fasting on cognition in healthy adults. However, a 2022 study surveyed 411 older adults and found that lower meal frequency (fewer than three meals per day) was associated with less evidence of Alzheimer's disease on brain imaging.
Some research has suggested that caloric restriction may have a protective effect against Alzheimer's disease by reducing oxidative stress and inflammation and promoting vascular health.
When looking at the effects of general energy restriction (rather than intermittent fasting specifically), the evidence is mixed. Among people with mild cognitive impairment, one study showed cognitive improvements when participants followed a calorie-restricted diet for 12 months.
Another study found that a 25% calorie restriction was associated with slightly improved working memory in healthy adults. But a recent study that looked at the impact of caloric restriction on spatial working memory found no significant effect.
Seek professional advice
Studies in mice support a role for intermittent fasting in improving brain health and aging, but there are few human studies and the evidence we have is mixed.
Rapid weight loss associated with caloric restriction and intermittent fasting can lead to nutrient deficiencies, muscle wasting, and decreased immune function, especially in older adults whose nutritional needs may be greater.
In addition, prolonged fasting or severe calorie restriction could pose risks such as fatigue, dizziness, and electrolyte imbalances, which could aggravate existing health conditions.
If you are considering intermittent fasting, it is best to seek the advice of a health professional such as a dietitian who can provide guidance in structuring fasting periods, timing of meals and nutrient intake.
This ensures that intermittent fasting is addressed in a safe, sustainable way, tailored to individual needs and goals.
