The Power of Fasting: How a 3-Day Fast Can Transform Your Body

Research continues to accumulate evidence that intermittent fasting, longer than the daily fasting we experience while sleeping, may have health benefits. When food is withheld for a sufficient amount of time, the body switches energy sources and begins to consume fat stores. This helps with weight loss, which in turn improves hypertension and glucose levels. However, long-term follow-up studies are lacking to determine if this eating style can be maintained over time. Some studies have also shown benefits to the immune system, cardiovascular health, and insulin resistance, which is behind diabetes, but the mechanisms explaining these observations are not well understood.

Technologies that measure proteins in the blood offer the possibility of investigating the molecular changes that occur when we fast, to better understand its benefits and potential risks. This allows us to begin to clarify some of the most persistent doubts about the true mechanisms behind intermittent fasting, a practice that has received so much attention lately. Now, an international team of scientists has published an article in Nature Metabolism explaining how they had 12 volunteers drink only water for seven days. They measured the levels of around 3,000 proteins before, during, and after fasting and crossed those data with genetic information from other studies to estimate the benefits that could be obtained with the observed protein variations.

Although it’s only 12 subjects, the methodology allows for a wealth of information to be collected. As expected, the study participants lost weight, an average of 5.7 kilograms, split between fat and muscle. However, three days after stopping the fast, they regained muscle mass but not fat. In addition to this striking fact, the scientists, led by Claudia Langenberg from Queen Mary University of London, observed a change in the composition of proteins in the blood from the end of the second day of fasting and the beginning of the third.

Exponential Increase in Beneficial Proteins

The increase in beneficial proteins is exponential from the third day of fasting, and researchers hypothesize that these changes are not only related to weight loss, but also to other mechanisms. For example, proteins that prevent neuronal deterioration are affected. According to Maik Pietzner, co-author of the study, “the message of these results is that you need two or three days of fasting for this change to occur, for internal resources to be utilized, and possibly for different metabolic programs to begin in different organs.”

Simpler than Counting Calories

Pietzner believes that reducing the hours of food intake is a simpler way to reduce daily caloric intake than counting calories at each meal. However, longer fasts may have beneficial effects with specific applications. For example, fasting has been shown to have an effect on the treatment of resistant epilepsy, and may also have benefits for other diseases such as rheumatoid arthritis.

Medical Supervision

However, researchers also observed an increase in the risk of thrombosis with prolonged fasting. Therefore, it is important for people to be aware of the need for medical guidance when applying such extreme interventions, as there may be individuals with a higher risk of adverse consequences.

Significance of the Study

Benjamin Horne, a professor at Stanford University, notes that due to the small sample size of the study (only 12 participants), it is unclear how significant the three-day delay in the effect of fasting is. Other studies with larger samples have documented changes in proteins in the blood 20 or 24 hours after the start of a water-only fast.

Importance of Professional Guidance

Malu Martínez Chantar, a researcher at the CIC bioGUNE in Derio, Spain, also warns of the small size of the cohort and recalls the positive effects of shorter fasts detected in patients with autoimmune diseases or when done before or after chemotherapy in people with cancer. However, she emphasizes that any nutritional intervention should be supported by a professional, as the ketone bodies generated by fasting can have a negative impact on some individuals.

Future Research Directions

One of the goals of studies like the one led by Langenberg is to identify the proteins that are modified by fasting in order to design interventions that can alter the same mechanisms without requiring a person to go without water for seven days. The development of these precision therapies could be beneficial for everyone, but especially for people who cannot undergo such a fast due to poor health or other reasons.

Long-term Effects

Martínez Chantar believes it is necessary to know precisely the changes that occur in our body when we stop eating, also in the long term. “It is necessary for these studies to be carried out over a longer period because we do not know what the effects of sustained fasting are on aspects such as longevity.”

Remembering the Importance of Professional Guidance

As research on the effects of fasting on the body continues to unfold, it is important to remember the warning of one of the gurus of the field, biochemist Valter Longo: “Whether fasting is good, bad, or neutral means nothing; like eating, some types of fasting are very good and others very bad.”