WHAT POSITIVE EFFECTS DOES FASTING HAVE ON YOUR MENTAL HEALTH AS WELL AS ON YOUR PHYSICAL HEALTH? HOW TO MAINTAIN A BALANCED AND HEALTHY DIET DURING PROLONGED FASTING PERIODS - Written by Elissar Souweid, BIO-R® Nutritionist & Research Specialist

In the last 10 years, fasting has gained huge popularity in both the public and the science community amid its promising benefits on both physical and mental health.

Fasting is actually not new; it has been and remains a common religious practice since the 5th century BC, with the Greek culture claiming that abstinence from food and drinks for a period of time helps nourish the spirit and the mind, suppressing symptoms of illnesses as well as supporting recovery processes.

Intermittent fasting is the trendiest art of fasting nowadays. It has been increasingly followed for disease prevention and therapy (i.e. diabetes, coronary heart disease), weight loss, healthy ageing, improving cognitive function, and many others.

What is Intermittent Fasting?

By definition, Intermittent Fasting is refraining from or significantly limiting calorie intake through repeated intervals, and it can take different forms:

• Daily time-restricted eating: the most prominent example is 16:8, when a person eats moderately within an 8-hour eating window (usually 2 meals) and fasts for 16 hours.
• 5:2 diet: also known as periodic fasting; when a person eats moderately 5 days a week and has very low caloric intake (approximately 500-600 Kcal/day) on 2 non-consecutive days.
• Alternate date fasting: alternating between one day of moderate food consumption and one day of low caloric intake (approximately 500-600 Kcal) through only one meal, usually in the middle of the day.
• Weekly one-day fasting: also known as “Eat-Stop-Eat”, is when the person avoids calories from food and drinks for one day per week (just drinking water and other non-caloric fluids) and eats moderately the last 6 days of the week.

Intermittent fasting and health:

There is emerging literature from human and animal studies on the benefits of intermittent fasting on metabolic health, general physical fitness as well as mental well-being. Even though the results are not conclusive in all the subjects, in certain topics, they are very promising.

Here is a summary of how intermittent fasting influences some of the health aspects:

• Weight loss: most of those following intermittent fasting are doing so to lose weight. It is actually a clever plan; weight loss is certainly an evidence-based benefit of intermittent fasting; human studies have confirmed that following this regimen in obese and overweight individuals is associated with faster weight and body fat loss in the short term. More studies are still needed to evaluate its effect in the long term.
• Cardiovascular diseases and diabetes: Evidence around this topic is still not conclusive and is arising mainly from animal studies. However, it’s certain that losing weight through intermittent fasting improves biomarkers like glycemia (HbA1C, fasting blood glucose, insulin sensitivity), lipid profile (total cholesterol, HDL, LDL, triglycerides) and lowers blood pressure.
• Gut microbiome: Intermittent fasting is shown to cause a positive shift in the profile of the gut microbiome by increasing the abundance of beneficial bacteria (i.e., Lactobacillus and Bifidobacteria) and the bacterial diversity itself. Given the role of the gut microbiome in our bodies, this shift would certainly induce positive physical and mental consequences ( i.e. absorption of nutrients, body inflammation, digestive symptoms, immune system, stress, and anxiety levels).
• Brain health and function: Second to weight loss, intermittent fasting is gaining huge publicity as a strategy to improve several brain functions (memory, cognition, concentration). But this claim is not yet backed by science; what is known so far is that intermittent fasting can slow down the progression of Alzheimer’s disease and possibly improve the physical and mental status of people with Parkinson’s, ischemic stroke, Autism, and anxiety disorders. When it comes to healthy people, intermittent fasting hasn't yet been proven to show benefits to cognition.
• Oxidative stress and inflammation: when limiting the calorie intake to fewer hours per day or days per week, the mitochondria (the powerhouse in our body cells) will be producing fewer free radicals resulting in reduced oxidative stress. At the same time, with long fasting hours, the process of autophagy or cellular recycling and rejuvenation will be activated. This enhances the body’s resistance against inflammation and related inflammatory diseases (i.e. diabetes, cardiovascular diseases, cancer, renal insufficiency).
• Longevity: intermittent fasting is emerging among the public as the ultimate longevity diet. The reality is it is still very early to come to this conclusion. What is known till now is that some forms of intermittent fasting can prevent or slow the progression of age-related diseases (diabetes, Parkinson’s, blood pressure) and initiate autophagy, thus endorsing health span and longevity. But evidence on the impact of intermittent fasting on the hallmark of ageing (nutrient-signalling pathways, telomere length, DNA methylation) is still very basic.

The metabolic switch

Intermittent fasting’s effect on the body is mainly a consequence of the change in the source of energy used by the body between the feeding and the fasting phases, also known as a metabolic switch, accompanied by cellular and molecular changes.

So here are the main stages that our body goes through when following the intermittent fasting regimen:

• Fed state: During eating periods, the body relies on glucose (from carbohydrates, fruits, and vegetables) as a main source of energy. Excess glucose is converted and stored in the liver and muscles as glycogen stores in the first step and as fat (triglycerides) second.
• Early fasting state lasts between the 4th to the 18th hour after eating. As the body completely utilises the glucose from the last meal, it goes into converting the glycogen stores into glucose for energy by a process called glycogenolysis. This stage is mainly achieved when adopting a time-restricting eating pattern (i.e. 16:8).
• Fasting state: this occurs between 18 and 48 hours after the last meal. Here the body’s storage of glucose and glycogen is depleted, so it switches to lipid metabolism, converting fat (mainly triglycerides) into ketone bodies as an alternative source of fuel for the various body tissues, especially the brain.
• Starvation (long-term fasting state): it occurs 48 hours after the last meal; this is when the body continues using body fat for ketones production and starts using amino acids as an additional source of energy.

What to factor when following intermittent fasting

Caloric intake

All the body changes and health benefits attributed to intermittent fasting are basically the results of calorie restriction which induces variation in hormone levels, metabolism, cellular processes, and gene expression. So, to benefit from intermittent fasting, it is important to keep an eye on the amount and type of food consumed during the feeding window.

Here, moderation and routine are the keys to success. A healthy meal plan with sufficient fibre (i.e. vegetables, whole grains) and lean protein intake is helpful to maintain satiety for longer periods, limits the risk of ravenous hunger ending in overconsuming calories through little snacks and drinks, and topping up the daily calorie consumption.

In addition, a routine of meal planning (number of meals and snacks per day) would facilitate hormonal homeostasis, digestion, and metabolism, favouring and lessening the feeling of extreme hunger that normally ends up with overeating.

Timing of meals:

Similarly to the type and quantity of food intake, the timing of meals is another important factor to consider when following intermittent fasting. Respecting the circadian rhythm and favouring the eating periods within the daytime (morning until early evening) is ideal to benefit from this diet, especially in terms of weight loss, controlling glycaemia, and reducing blood pressure.

This is mainly due to the changes that happen in our organ systems between day and night time (i.e. the capacity to digest and metabolise food, control body temperature, and hormone secretion).

Most of those following intermittent fasting find it easy, as they naturally skip breakfast because they are not hungry or they are busy, so they push the eating window to the afternoon and night when naturally eating and drinking are part of socialising. Here one should be aware that intermittent fasting is less likely to induce health benefits. On the contrary, it may lead to digestive discomfort and poor sleeping quality. In this case, as a general rule, one should aim for early dinners around 18:00-20:00 as the last meal of the day.

Possible side effects of intermittent fasting:

As with any other dietary approach, intermittent fasting is not a good fit for everyone and can be accompanied by certain side effects:

• Headache: It is the most common side effect of intermittent fasting; it usually occurs the first days of adapting to this regimen, generally in the alternate-day fasting form, and more likely with people who chronically suffer from headaches.
• Low energy, tiredness and irritability: common side effects of following intermittent fasting, especially in women. These symptoms usually result from severely limiting calories during the eating window or very long hours of fasting.
• Extreme weight loss and malnutrition: it is a real challenge to provide the body with all nutrient requirements within shorter eating intervals, which may lead to several deficiencies and unhealthy weight loss (rapid pace and losing muscles). This can be dangerous for older adults, who have higher requirements of protein, vitamins, and minerals and are more susceptible to infections and fractures. Unsupervised intermittent fasting in the elderly can negatively affect their energy levels, bones, and overall immune system.
• Hormonal imbalance and weight gain: Intermittent fasting affects both levels and frequency of certain hormones, especially those involved in controlling hunger and satiety (ghrelin, leptin, insulin) and stress (cortisol). Extreme fasting patterns can cause disturbances in these hormones and the whole circadian rhythm leading to increased appetite and slower metabolism, hence weight gain, an undesirable consequence in most cases.
• Constipation: this can be a consequence of following intermittent fasting if the person is not consuming enough fibre during the feeding window and enough fluids.

It’s not for everyone

Little is known about intermittent fasting in certain target groups like kids, pregnant and breastfeeding women. Therefore, it should be avoided in those life cycles, as limiting food intake causes various nutritional deficiencies which impair the development of the foetus, newly born, or children in their growing years, and unclear health consequences later in their life.

People on medication should always consult their healthcare professional before following intermittent fasting. Some medication should be taken with food to improve absorption, to avoid gastric symptoms (nausea, stomach irritability). In other cases, like medication for diabetes and blood pressure, limiting food intake for long periods can result in hypoglycemia and electrolyte imbalances.

People with a history of or currently suffering from eating disorders should also avoid following intermittent fasting because it’s a restrictive model. A recent study found that people engaging in intermittent fasting show certain eating disorders symptomatology.

Tips and tricks

• If someone is interested in trying any form of intermittent fasting, it is important to check first if it’s safe to do so, if there are any risk factors, and if it is sustainable and fits the person's lifestyle (physical activity, working hours, social engagement).
• Avoid processed food: Generally and not restricted to intermittent fasting, the diet should be mostly composed of natural ingredients to maximise the intake of vitamins, minerals, and antioxidants for their health benefits.
• Make your meal plan balanced and various: the diet should include the main food groups (vegetables, fruits, fat, protein, and whole grains) to ensure the body is getting enough macronutrients (proteins, fat, carbohydrates) and micronutrients (vitamins and minerals). Varying in the same food group is also recommended, especially in plant-based food, to profit from the benefits of the various antioxidants they contain.
• Stay hydrated: Maintain a good energy level through the fasting periods through sufficient hydration, mainly from water, unsweetened herbal infusions, soups, and vegetables with high water content. Dehydration can cause fatigue, dizziness, and other symptoms and make sticking to the diet more challenging.
• Exercise, sleep enough, and avoid focusing just on your diet so its implementation becomes smooth and sustainable.

In BIO-R®, we support our clients in their lifestyle choices; together, we go through a detailed assessment to define the safety of a certain diet plan, we study their eating habits and health objectives, and we build them a personalised meal plan that supports both their physical and mental health while fitting with their lifestyle.