The Science of Fasting

By: Anshu Bahanda

To truly understand the effects of fasting on our body, it's crucial to consider its evolutionary roots. Our forebears, shaped by cycles of feast and famine, evolved sophisticated physiological responses to these variable conditions. Today, amidst a backdrop of constant caloric availability, fasting serves as a bridge to these ancient adaptive systems, potentially paving the way for improved health. A 2019 study from Germany's Buchinger Wilhelmi clinic revealed that extended fasts ranging from four to 21 days significantly reduced body weight, blood pressure, blood sugar levels, and abdominal fat, while also elevating physical and emotional well-being.

On my podcast, Dr Sepp Fegerl, GP, Holistic Health in Salzburg, Austria, who's trained in Modern Mayr medicine, explains fasting from a medical point of view. “Fasting medicine is an anti-inflammatory treatment, an anti-inflammatory therapy. And inflammation is non-infectious. Diseases that are related to inflammation are seen worldwide and are still responsible for more than 74% of all mortalities. With fasting there is no maldigestion, fermentation or decay inside the intestine. Breathing gets better, cognitive possibilities improve. Overall, it is a rather positive, life-changing experience because it’s so simple. You can practise it wherever you are, whatever culture you are in.”

What happens when we fast?

Fasting sets off a chain of reactions that impact multiple systems within the body. “As an individual refrains from caloric intake, the most immediate effect is the depletion of glucose reserves in the bloodstream and the liver. In search of an alternative energy source, the body turns to its glycogen stores, breaking them down into glucose molecules to sustain basic metabolic functions. But glycogen reserves are finite, and as the fasting period persists, the body pivots towards a more sustainable source of energy; fat. Through a process known as lipolysis, adipose tissue releases fatty acids into the bloodstream, allowing tissues and organs to derive their energy from these lipid reserves,” says California-based Dr Ronesh Sinha, internal medicine physician, author of The South Asian Health Solution, and an expert on insulin resistance.

Remarkably, the human body skilfully manages this metabolic shift, utilising and processing fat with remarkable efficiency. Simultaneously, fasting sets off a hormonal dance orchestrated by a delicate symphony of signals. Insulin levels decline, reducing the uptake of glucose into cells, while glucagon and other hormones surge to promote the release and utilisation of stored energy. Additionally, fasting prompts the secretion of the growth hormone, which enhances the preservation of lean body mass during the fasting phase. Beyond energy metabolism, fasting touches on other critical facets of our physiology.

Autophagy, a process of cellular self-cleansing and recycling, gains prominence during fasting. Japanese cell biologist Dr Yoshinori Ohsumi was awarded the 2016 Nobel Prize for his pioneering work in autophagy. Dr Ohsumi's win made the topic of fasting more popular.  Since 2016, there is more interest in figuring out the exact mechanisms by which dietary restriction slowed down the ageing process. Says Dr Sinha, “Moreover, fasting has profound effects on our gut flora, the trillions of microbes residing within our digestive tract. As food intake wanes, the gut microbiome experiences a shift, with certain species thriving and others diminishing.”

More than just cutting calories

Fasting isn't just another diet trend; it's a journey that takes our body through intricate biological pathways and even reshapes our cognitive terrain.

Sure, we've all heard of calorie counting as a go-to method for shedding those extra pounds. But fasting dances to a different tune. When our body starts rummaging for energy sources during a fast, it doesn't just deplete any energy; it smartly turns to our fat reserves. This leads to a twofold effect: a quick breakdown of those pesky fat tissues and a commendable job of hanging onto our lean muscle mass. That lean muscle? It's the unsung hero in ensuring our weight loss isn't just a fleeting moment but a lasting triumph.

Fasting's influence on brain function extends to the realms of mood and mental health. Dr Ronny Tri Wirasto, Psychiatrist and Chairman of the FK-KMK UGM Mental Medicine Specialist Education Study Programme (Indonesia) states “Fasting has a direct effect on relieving stress. The consumption of regulated food also influences the way of thinking, it becomes more organised. Some patients report improvements in focus, concentration, and mental clarity.”

The risk of nutrient deficiencies is a significant concern when considering fasting, underscoring the importance of a well-planned and balanced approach. Dr Fegerl illustrates this point vividly: “Imagine that you start fasting and you're already suffering from a deficiency in trace elements that are key in the enzymatic performance of your liver, such as selenium, zinc or copper, for example. That person's body – especially the mitochondria – suddenly works on alternative metabolic strategies. They try to compensate for the deficiency and increase the risk of developing a myocardial infarction (stroke) or the aggravation of a mental illness.”

Before embarking on a fasting journey, it's paramount to seek expert guidance to ensure safety and efficacy.

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