Intermittent fasting (IF) describes the process of eating between set windows of time – giving the body optimal time to enter a state of fasting – time not spent on ingesting or digesting food. We all fast regularly to a certain degree daily, the biggest window being from the time of our last meal to the time of our first meal the following day.
One of (if not) the most popular forms of intermittent fasting is the 16:8 fast. This describes fasting within a 24-hour period, characterised by 16 hours of fasting, with an 8 hour window left open for eating. Typically, this window is spent around 11am – 7pm, or 12pm – 8pm (though this time is somewhat flexible to individual needs). This method of fasting is perhaps the easiest to adopt and can be maintained long-term.
As the name suggests, this describes a day of fasting followed by a day of regular eating. This can be considered a little extreme approach to IF, as the fasting day is usually a complete fast, or spent consuming around 25% of your regular caloric intake.
Again, this may be considered a little extreme, as it attempts to combine days of complete fasting (or very little caloric intake) interspersed with days of regular eating. As the name suggests, it entails five days of regular eating followed by two days of complete fasting or heavy caloric restriction.
Motility refers to the movements (contractions) made by your intestines which result in the passing and excretion of your food/waste from your body. When motility is optimal, bowel movements become regular, preventing feelings of bloating, heaviness and gassiness. Further to this, regular bowel movements encourage the health of our gut bacteria, and decrease the risk of foods fermenting in our gut leading to small intestinal bacterial overgrowth (SIBO) and/or small intestinal fungal overgrowth (SIFO).
IF leads our bodies into a healthy period of starvation. In this period, the body is bereft of carbohydrates and sugars to use as energy, so it will turn to the fat cells within our body to source its energy needs. As the fatty acids are released from the cells and converted to energy, the body enters a healthy state of ketosis (the benefits of which can be found here). This state promotes weight loss, most of which is achieved through fat loss (a giant plus).
Furthermore, IF necessarily enforces caloric restriction, which, simply put, indicates that the body will be in caloric deficiency – energy spent will exceed energy consumed – another state which leads to weight loss.
Intermittent fasting increases both Brain Derived Nootropic Factor (BDNF) and Glial Cell Derived Neurotrophic Factor (GDNF) – both of which have been shown to ameliorate and attenuate neuronal damage. These are two important chemicals involved in the protection and development of our brain, and are heavily involved with both neurogenesis and neuroplasticity (the process of growing new brain neurons and rewiring of the brain circuitry), as well as working to prevent such neurological conditions associated with ageing such as Parkinson’s and Alzheimer’s disease.
Further to this, both BDNF and GDNF positively contribute to learning, memory and cognitive function, whilst also exhibiting anti-depressive and anxiolytic (anxiety relieving) activity.
Another great way of boosting BDNF is through the use of low carbohydrates diet – which you can read about here.
IF has been shown to decrease levels of insulin resistance and boost metabolic health. Decreases in insulin resistance vastly improve the prevention of developing type two diabetes, obesity and a host of other metabolic conditions. To consolidate this further, intermittent fasting has also shown to increase the metabolic rate (the rate at which our body breaks down substances to extract energy, vitamins and minerals) from 3.6-14%. Improved metabolic health is associated with greater overall health and well being, whilst metabolic dysfunction is heavily associated with the onset of diabetes, obesity and mental illness.
IF and caloric restriction promote the expression of glutamic acid decarboxylase – the enzyme responsible for converting the neurotransmitter glutamate into GABA. This is an extremely important conversion that is vital for our mood, cognition and general well-being. High levels of glutamate are associated with anxiety, brain fog and panic – whilst the opposite is true for optimal levels of GABA. GABA is sometimes referred to as the ‘calm’ neurotransmitter, helping us to relax, wind-down, relieve anxiety and promote sleep.
GAD (red+green).
Studies have shown that IF improves several factors contributing to overall cardiovascular health including blood pressure, triglyceride levels, total blood lipid levels, blood sugar levels and inflammatory markers. These are all significant contributors to the development of heart disease. Furthermore, IF, as a preventative measure against the development of type two diabetes and obesity, increasingly bolsters it’s protective measures against heart disease, as both diabetes and obesity greatly increase the risk of the development of heart disease.
IF has been shown to significantly decrease levels of oxidative stress markers and inflammatory markers. This is an extremely important finding as both oxidative stress and inflammation play critical roles in many chronic diseases, and are strongly connected with neurodegenerative disease and ageing. IF decreases the stress and impact of these markers on our bodies whilst at the same time promoting enzymatic expression of important digestive enzymes that all aid in breaking down/absorbing our food and promoting overall metabolic health.
IF is a fantastic way to not only lose weight, but improve overall health and well being. As with most things regarding self management and development, a little bit of willpower and discipline is required, but is far outweighed from the rewards they reap.