What is Fasting?

Fasting seems to be in everyone’s “mouth” these days – or rather, not in anyone’s mouth – because fasting entails the abstinence from any food and possibly even drink. 

Fasting is not new – in fact, it is possibly as old as humanity, evolving from the simple scarcity of food during parts of the year. So evolutionary, we are likely well-equipped to withstand a fast, and some may argue that we “need” to fast to be healthy. 

What are the health benefits of fasting?

The health benefits for fasting are plenty:

  • Improved insulin sensitivity
  • Longevity
  • Improved cardio-vasular health
  • Weight loss – especially fat loss with Improved muscle to fat ratio
  • Mental clarity
  • Decreased oxidative stress – a process involved in many diseases like Dementia, Diabetes, cardiovascular disease, autoimmune disease, etc.
  • Improved effectiveness and reduced toxicity of chemotherapy and radiation
  • Athletic performance? Exercise can induce a deeper state of ketosis during the fast, but whether athletic performance improves with fasting is still a matter of debate. 

How does fasting improve health?

The mechanism by which fasting accomplishes its benefits, is a change in cellular biochemistry: shorter fasts induce the switch form glucose and glycogen fuelled energy metabolism to ketosis and thereby reduce the body’s need for insulin. Longer fasts activate autophagy (“self-eating) and apoptosis (programmed cell death) of cells that have become unnecessary or dysfunctional. It is the bodies way of systemically cleaning up damaged cells – “the ultimate detox”. 

What are the different ways to fast?

There are many different ways of fasting: 

  • Intermittent fasting: (actually, the correct term is time restricted eating, TRE): choosing to eat for a set window of time only. Common rations between fasting hours and and feeding hours are 16:8, 18:6 and 20:4.
    • Breakfast vs Dinner fasting: Popular fasting times are during the night until the early hours of the afternoon, i.e. the “breakfast fast”. Most people find breakfast fasting fairly easy, and it does not impact the more social dinner meal. However, the body is most sensitive to food – especially carbs and sugar- in the morning. Worse, studies have shown that skipping breakfast IMPAIRS insulin sensitivity, increases total and LDL (“bad”) cholesterol and may even lead to weight gain.
  • Alternate day fasting: fasting for 24h every other day. The benefits seem to be similar to intermittent fasting on weight loss; however, there seems to be no change with alternate day fasting and inflammation in colitis (at least not for mice).
  • Prolonged fasting (semantically, this is the real intermittent fast): is fasting that lasts upwards of 48h. Common fasting times are 2 days per week, 7 days per month or fasts up to 14 days or longer. Prolonged fasting usually omits all intake of food, but allows water and may allow juices or broth. The benefits of prolonged fasting go beyond weight loss, with profound changes in cellular metabolism. Autophagy and apoptosis are initiated usually after 48h of food deprivation, and has shown beneficial effects on serious chronic diseases like cancer, multiple sclerosis and irritable bowel disease. A word of caution: Prolonged fasting can cause nutrient depletion and is not for everyone. Classically prolonged fasting includes careful preparation of body and bowels to tolerate the fast and tolerate re-feeding after the fast – so prolonged fasting is best done with medical supervision.
  • Fasting mimicking diet: this diet was developed by Dr. Valter Longo. The Fasting Mimicking Program is a five-day program, which includes specific (plant based) foods, at a very low calorie content. The foods are selected such that the body does not recognize that it is being fed, causing a fasting mode, without the -psychological- restrictions of complete food deprivation. The benefits are remarkably similar to prolonged fasting. 
  • Religious fasting: is primarily an exercise of devotion: to willingly renounce oneself, for a definite period of time, from all bodily appetites (including food, drink, smoking, sexual relations) in order to form spiritual discipline and self-control). While the paradigm goes deeper than simple fasting, the health benefits include improvement in blood pressure, blood lipids, insulin sensitivity, and biomarkers of oxidative stress. The degree of improvement varies, depending on the specifics of the religious fast. 

Is fasting for me?

Whether you should fast or not depends on your situation, your health and your goals – the evidence for the benefits of fasting are growing fast and wide – and the choice is yours. 

Good reads and further info:

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