In the past decade, intermittent fasting has become very popular. Many of us have heard about the purported health benefits from adopting these practices, including benefits to fat loss, muscle gain, insulin sensitivity, and cellular repair. Recently I’ve come across several studies that show the method might be as good for the mind as it is for the body.
Quality of Life Improvements in Nonobese, Healthy Individuals
In a multisite randomized clinical trial published in JAMA Internal Medicine in June 2016, scientists investigated the impact of fasting on mood, quality of life, sleep, and sexual function. The participants were healthy nonobese adults who were either placed in a 25% calorie restricted group (145 participants) or an ad libitum control group (75 participants). Data was collected at baseline, 12 months, and 24 months. The individuals in the calorie-restricted group met with a health coach to assist them in sticking to the diet plan, and they were also provided with food for the first few weeks to help them learn about portion sizes and which meals are most nutritious and filling. The control group received no coaching or education.
Mood, stress, sleep, and sexual function was measured using self-reported questionnaires. By month 24, participants in the calorie-restricted group had lost an average of 7.6 kg, while the participants in the ad libitum group lost an average of 0.4 kg. Participants in the calorie-restricted group reported a significantly improved mood, reduced tension, improved general health, and enhanced sexual drive and relationship at month 24. They also said that they experienced improved sleep duration by month 12. Calorie restriction had no adverse effects on quality of life in this study.
Improvement in Mood Among Older Men
In an interventional study, a total of 32 males (aged 59.7 + 6.3 years, with a BMI of 26.7 + 2.2 kg/m2) were randomized to either the fasting calorie-restricted (FCR) group or to a control group for three months. Participants in the control group were asked to maintain their current lifestyle. The Profile of Mood States, the Beck Depression Inventory-II, and the Geriatric Depression-Scale-15 were used at baseline, week 6, and week 12 of the intervention. Significant decreases in tension, anger, confusion, and total mood disturbance, as well as improvements in vigor, were observed in participants in the FCR group compared to the control group. However, no significant changes in mean depression scores were found. Weight was decreased in the FCR group by 3.8%, BMI was reduced by 3.7%, and the average percent of body fat fell by 5.7% during the study.
Muslim Sunnah Fasting and Depression
In a third study, calorie restriction of 300-500 kcals/day combined with two weeks of Muslim sunnah fasting was studied among twenty-five healthy Malay men with no chronic diseases and an average BMI of 23.0. The men were randomized to either the FCR group or a control group.
- Quality of Life was measured using the Short-Form 26
- Sleep quality was determined using the Pittsburgh Sleep Quality Index
- Mood was assessed via the Beck Depression Inventory II
- Depression was measured by the Perceived Stress Scale.
The FCR group experienced a significant reduction in body weight, BMI, body fat percentage, and depression. The participants in the FCR group also reported significantly increased energy, but experienced no changes in sleep quality or stress level.
Mood Improvement Among Chronic Pain Patients
In a controlled exploratory study of 52 inpatient subjects with chronic pain and metabolic syndrome, more than 80% of participants reported mood improvement after five days of fasting. However, whether or not mood improvement occurred after eight days of fasting (350 kcals/day) was found to depend on a genetic polymorphism. This improvement in mood was independent of weight loss, decreased leptin level, or increase in plasmatic cortisol.
Scientific Reasoning for Improvement in Mood Associated with Fasting
- The improved mood might result largely from the improved sleep associated with fasting, which is measurable by polysomnography in terms of limb movement and nocturnal awakening.
- One study reported an increase of endogenous opiate production in rats by five levels during the first 24 hours of fasting, decreasing to two levels by 48 hours (still impressive).
- The decrease in cerebral glucose is thought to promote neurogenesis and synthesis of neurotrophic factors, receptors for neurotransmitters, and chaperone proteins. Levels of brain-derived neurotrophic factor, which is involved in the regulation of serotonin metabolism, synaptic plasticity, improved cognitive function, and the brain’s ability to resist aging, increase with fasting.
- Catecholamines and glucocorticoids are released in large amounts during the first seven days of a fast. In response, the brain’s cellular mechanisms of stress resistance are activated to protect itself against these hormones.
Risks of Fasting
Intermittent fasting is not appropriate for everyone and some research has determined that it is better for men than it is for women overall. It is imperative that anyone considering intermittent fasting speak to their doctor and a registered, licensed, dietitian before starting. Certain medical conditions and medications can make this type of eating pattern quite dangerous. A registered dietitian can help you plan your meals so that you maximize nutrient intake and avoid nutritional deficiencies. Dehydration can easily occur if one is not vigilant about drinking enough fluid when fasting. Headaches and heartburn are common during fasts. Intermittent fasting has been criticized as leading some individuals to overeat on non-fasting days, which might cause feelings of guilt and shame and could play a part in the development of an eating disorder. No one under the age of 18, pregnant women, individuals with a body mass index of less than 18.5 or more than 40, people with diabetes who are on insulin, people with a serious comorbid condition (such as cancer), or those recovering from surgery should attempt to fast.