The goal of intermittent fasting is to improve health by controlling when you eat and when you fast. This eating pattern alternates between periods of eating and not eating, aiming to take advantage of the benefits that fasting can bring.
While many people use intermittent fasting for physical health benefits like weight loss and improved metabolism, it also has significant effects on mental health.
This article aims to provide an overview of the psychological effects of intermittent fasting on mood and stress, and how this approach can impact your emotional health.
Intermittent Fasting Background
Intermittent fasting is an approach to eating that involves switching between periods when you don’t consume any calories and periods when you eat as usual or limit the amount you can eat on certain days. It’s primarily known for its potential benefits in weight management and metabolic health. In creating distinct periods of fasting and eating, intermittent fasting can help regulate insulin levels, improve fat burning, and potentially lead to weight loss.
You might encounter several types of intermittent fasting. For example, the 16/8 method involves fasting for 16 hours each day and eating during an 8-hour window. Another popular approach is the 5:2 diet, where you eat normally for five days of the week and restrict calories on two non-consecutive days. The Eat-Stop-Eat method involves fasting for 24 hours once or twice a week, while alternate-day fasting has you alternate between days of normal eating and fasting.
The flexibility of these methods is what makes intermittent fasting an appealing choice for many people.
Physiological Responses To Intermittent Fasting
Fasting induces a range of physiological responses that you can experience in distinct stages. Immediately after eating, your blood glucose levels rise, prompting your pancreas to release insulin, which helps your cells absorb glucose for energy or storage.
As you transition into early fasting, typically within 6-12 hours, your body begins to break down glycogen stored in your liver and muscles to maintain blood sugar levels. Your insulin levels drop, reducing glucose uptake and encouraging your body to seek alternative energy sources. During short-term fasting, from 12 to 24 hours, your body starts to oxidize stored fats, breaking them down into fatty acids and ketones1.
Your liver produces ketones, which become a significant energy source, especially for your brain. Hormonal shifts also occur, with an increase in growth hormone secretion to aid fat metabolism and muscle preservation, and a potential rise in cortisol to mobilize energy stores2,3.
As fasting continues into the intermediate stage, 24 to 48 hours, your ketone levels in the blood continue to rise, enhancing energy availability for your brain and muscles. Autophagy, the process of cellular repair and maintenance, intensifies, while markers of inflammation begin to decrease, reducing your risk of autoimmune diseases4.
In the prolonged fasting stage, 48 to 72 hours, autophagy peaks, significantly improving your cellular function and longevity. Your immune system regeneration is triggered, and levels of insulin-like growth factor 1 (IGF-1), associated with aging and cancer, decrease, which may contribute to increased lifespan and reduced cancer risk5.
Extended fasting beyond 72 hours maximizes your fat oxidation, with ketone production at its highest. Your stem cells, particularly in the gut and immune system, are activated, promoting regeneration and repair.
Hormonal adjustments continue, potentially improving your appetite regulation and metabolic efficiency over time. However, during refeeding after prolonged fasting, there is a risk of refeeding syndrome, a potentially dangerous shift in fluids and electrolytes. Gradual reintroduction of food is crucial to avoid complications.
Your body becomes highly efficient at nutrient absorption, making the first post-fast meal particularly impactful for replenishing depleted stores. Your insulin and other hormone levels stabilize as you resume normal eating patterns, helping to regulate metabolism and energy balance.
Intermittent Fasting And Mental Health
Intermittent fasting protocols have been shown to influence various processes in the body, benefiting mental health.
Neurotransmitters and Fasting
Neurotransmitters and hormones are essential messengers for organ communication. Fasting can significantly affect these molecules.
Norepinephrine, which functions as both a neurotransmitter and hormone, is linked to alertness and attention. Fasting increases norepinephrine levels, potentially explaining the heightened focus many fasters experience1.
Serotonin, known as the “feel-good” neurotransmitter, regulates mood, appetite, and sleep. Higher serotonin levels during fasting can improve mood and reduce depressive symptoms.
Boosting Brain Health with BDNF
Fasting has been shown to increase the production of Brain-Derived Neurotrophic Factor (BDNF)6.
Elevated BDNF levels are linked to better cognitive functions, increased stress resilience, and protection against neurodegenerative diseases. This suggests that fasting might help enhance cognitive health and protect against age-related mental decline.
The Role of Autophagy in Brain Health
Autophagy, as previously noted, is a vital process that cleans up damaged cells in the body.
Fasting stimulates autophagy, especially in the brain, promoting the removal of excess proteins and damaged mitochondria. This process helps optimize brain function and may reduce the risk of neurodegenerative diseases like Alzheimer’s7.
The Psychological Effects Of Intermittent Fasting On Mood And Stress
Human Studies on Fasting
In a study involving 1,422 people who underwent periodic fasting, participants reported better physical and emotional health and higher levels of ketones, indicating a shift from using glucose to ketones for energy.
A clinical trial with older men practicing intermittent fasting for three months found significant reductions in tension, anger, confusion, and overall mood disturbance, while energy levels improved compared to the control group.
Another study on patients with chronic pain found significant mood improvements in those who underwent an 8-day fast. Intermittent fasting (24 hours per week) in healthy people also showed significant improvements in health-related quality of life and reductions in depression and anxiety8.
Time-Restricted Feeding
Time-restricted feeding (TRF) has shown positive effects on mood. For example, TRF synchronized with the light-dark cycle was found to prevent brain inflammation and promote healthy mood states, even with disturbed circadian rhythms.
However, a study on obese adults practicing a 16:8 TRF pattern for 12 weeks reported no significant changes in adverse mental health outcomes.
In post-cancer treatment patients, early results suggested that TRF with a 10-hour eating window improved fatigue and mood8.
Alternate-Day Fasting
Alternate-day fasting (ADF) has also shown benefits for mood. A study on overweight and obese women found better psychological well-being and vitality after a 12-week ADF program. However, no significant effects were observed in tests measuring concentration, reaction time, and various mood aspects8.
Ramadan Fasting
Ramadan fasting, a religious practice involving intermittent fasting, has been linked to improved mood.
Studies have shown that Ramadan fasting affects mood states, fatigue, and daytime sleepiness, with changes in biological markers like BDNF and cortisol related to mood improvements. The gut-brain axis, which involves communication between the gut and the brain, has been suggested to play a role in these effects, with fasting diets changing the gut’s microbial makeup and their metabolic activities, which in turn influence mood.
A systematic review and meta-analysis also found that fasting, particularly during Ramadan, appears to positively affect stress, anxiety, and depression. However, the results can vary due to several factors. Research involving randomized controlled trials suggests that fasting may improve mental health, especially when combined with lifestyle changes. Further studies are needed to verify these findings and better understand how fasting influences mental health9.
Major Depressive Disorder Patients
A study examined how fasting affects people with Major Depressive Disorder (MDD), focusing on those with varying symptom severity.
It found that fasting led to mood improvements mainly in those with more severe symptoms (MDDhigh), while both MDDlow and MDDhigh groups experienced increased physical symptoms of stress. The MDDhigh group also showed greater increases in brain chemicals related to mood after fasting.
Although the study observed similar effects on stress for both groups, it mainly highlighted the benefits of fasting for mood and cognitive symptoms. Fasting might be a useful addition to treatments, particularly for those who don’t respond well to standard therapies10.
Short-Term Fasting
Some research shows that short-term fasting can lead to more negative emotions like depression, anxiety, anger, irritability, and fatigue, while reducing positive emotions and energy. For example, a two-day fasting study found that people felt worse and performed worse at work, but this was partly due to the distraction of fasting rather than just hunger.
On the other hand, other studies suggest that short-term fasting can improve mood. For instance, an 18-hour fast among healthy women showed increased positive feelings and a sense of achievement.
Another study found that fasting might help in overcoming fear and maintaining this effect for up to six months. Yet, some studies found no significant difference in mood between fasting and non-fasting days, or between people who fast and those who do not1.
Health Conditions That Should Avoid Intermittent Fasting
Certain disorders and health conditions may warrant avoiding intermittent fasting or requiring careful management if fasting is considered. These include:
- Eating Disorders: Conditions like anorexia, bulimia, and binge eating disorder can be exacerbated by fasting, potentially worsening unhealthy eating behaviors.
- Diabetes: Particularly for those with insulin-dependent diabetes or those on medication that affects blood sugar levels, fasting can lead to dangerous fluctuations in blood glucose.
- Hypoglycemia: Individuals prone to low blood sugar may experience severe symptoms during fasting.
- Chronic Kidney Disease: Fasting can put additional strain on the kidneys, which may not be advisable for those with kidney problems.
- Severe Gastrointestinal Disorders: Conditions like Crohn’s disease, ulcerative colitis, or severe acid reflux may be aggravated by changes in eating patterns.
- Pregnancy and Breastfeeding: Nutritional needs are heightened during pregnancy and breastfeeding, making fasting potentially risky.
- Certain Heart Conditions: Individuals with certain cardiovascular conditions may need to avoid fasting due to potential impacts on heart health.
- Autoimmune Diseases: Some autoimmune conditions may be affected by fasting, potentially leading to increased symptoms or flare-ups.
Potential Risks And Side Effects
In addition to mental and emotional effects, intermittent fasting can pose other risks and side effects:
- Nutrient Deficiency: Limited eating windows might make it difficult to get all essential nutrients, leading to deficiencies.
- Digestive Issues: Some people may experience constipation, bloating, or acid reflux due to changes in eating patterns.
- Blood Sugar Fluctuations: Fasting can cause unstable blood sugar levels, which may be problematic for people with diabetes or blood sugar issues.
- Dehydration: Without adequate fluid intake during fasting periods, dehydration can occur.
- Headaches: Dehydration or low blood sugar during fasting can lead to headaches.
- Fatigue and Weakness: Feelings of tiredness and reduced energy can be common, especially at the beginning.
- Impact on Physical Performance: Fasting might reduce physical performance or endurance, particularly if exercising during fasting periods.
- Effects on Hormones: Fasting can influence hormone levels, including those related to stress and reproduction, potentially affecting health.
Final Thoughts
Intermittent fasting can significantly impact mood and stress, affecting both physical and mental health. This eating pattern is known for benefits like weight loss and better metabolism. However, it also significantly influences psychological health.
Fasting can change levels of important chemicals in the brain, like norepinephrine and serotonin, which can improve alertness and mood. Fasting also increases Brain-Derived Neurotrophic Factor (BDNF), which helps with thinking and stress management. Additionally, fasting promotes autophagy, which is the cleaning up of damaged cells in the brain, potentially lowering the risk of brain diseases.
Despite these benefits, intermittent fasting can worsen certain mental health conditions, such as eating disorders. Other health problems, like diabetes, chronic kidney disease, and serious stomach issues, might also be negatively affected by fasting.
In summary, intermittent fasting can boost psychological health by improving mood and reducing stress, but it’s important to consider individual health conditions when trying fasting interventions.
