The Health Impact of Intermittent Fasting

Intermittent fasting (IF) has gained a lot of popularity in the health and wellness world recently. It is a dietary approach that involves fasting for a set period and eating within a designated window. The idea behind intermittent fasting is to give the body a break from constant energy consumption and allow it to tap into stored fat as an energy source.

Manuela Băbuș
Medical Writer
The Health Impact of Intermittent Fasting
source: Freepik

Evidence is accumulating that eating for 6 hours and fasting for 18 hours can trigger a metabolic switch from glucose-based to ketone-based energy, with increased stress resistance, longevity, and a decreased incidence of diseases, including cancer and obesity.

Intermittent fasting is an eating pattern that includes hours or days of no or minimal food consumption without deprivation of essential nutrients. 

Although intermittent fasting often results in reduced calorie consumption, weight loss is not the main driver of the health benefits observed in preclinical and clinical studies. The fundamental mechanism of intermittent fasting is metabolic switching, in which fasting triggers the body to switch its source of energy from glucose stored in the liver to ketones stored in fat.

The mechanism of intermittent fasting

During a period of fasting, the body initiates several physiological mechanisms to ensure survival and maintain energy levels. The primary source of fuel during fasting is stored glycogen in the liver and muscles, which can provide energy for up to 24 hours. Once the glycogen stores are depleted, the body enters a state called ketosis.

Ketosis is a metabolic process where the body starts using stored fats as an alternative source of energy. Fats are broken down into ketones, which can provide energy to the brain and other organs. This shift in metabolism allows the body to preserve muscle mass while utilizing fat stores for energy during extended periods of fasting.

Intermittent fasting operates on the principles of manipulating the body's fasting and feeding windows to optimize health and well-being. By alternating between periods of eating and fasting, the body goes through several changes that contribute to the potential benefits associated with intermittent fasting.

source: Freepik

There are several types of intermittent fasting 

The most popular type of intermittent fasting include:

 - the 16/8 method

- the eat-stop-eat method,

- the 5:2 method. 

  • With the 16/8 method, people fast for 16 hours and eat within an 8-hour window. 
  • The eat-stop-eat method involves fasting for one or two full days a week. 
  • The 5:2 method allows people to eat normally for five days of the week and limits calorie intake to 500-600 for the remaining two days.

The benefits of intermittent fasting

One of the main benefits of intermittent fasting is weight loss. By reducing calorie intake and giving the body a break from consuming energy, people can effectively shed a few pounds. 

Another benefit of intermittent fasting is that it can improve insulin sensitivity, which is crucial in stabilizing blood sugar levels and preventing the development of type 2 diabetes.

Intermittent fasting may help regulate appetite hormones, leading to reduced overall caloric intake and potential weight loss.

Intermittent fasting also has some impressive effects on the brain. By promoting autophagy (the process of cleaning out damaged cells and regenerating new ones), intermittent fasting may help reduce the risk of Alzheimer's disease and improve cognitive function.

Additionally, several studies have linked intermittent fasting to increased longevity and reduced inflammation in the body.

Some studies suggest that intermittent fasting can positively impact gut health by promoting a diverse gut microbiome, which is essential for digestive and immune function.

The Dangers of Incorrect Intermittent Fasting

Intermittent fasting can be an effective dietary approach, but when done incorrectly, it can pose several risks to an individual's health and well-being. It is crucial to understand the potential dangers associated with improper IF practices to ensure that this eating pattern is adopted responsibly and safely.

Nutritional Deficiencies: Incorrect intermittent fasting may lead to inadequate nutrient intake. Since IF doesn't prescribe specific food choices, individuals might not consume a well-balanced diet during their eating windows. This can result in deficiencies of essential vitamins, minerals, and other nutrients necessary for overall health.

Muscle Loss: Extended fasting periods or excessively restrictive eating windows may cause the body to break down muscle tissue for energy. This can lead to muscle loss, which is undesirable, especially for individuals aiming to maintain or build muscle mass.

Disordered Eating Patterns: Incorrectly following intermittent fasting can trigger disordered eating behaviors. Some people may develop an unhealthy obsession with food or experience anxiety about meal timings, leading to a negative impact on their mental and emotional well-being.

Hormonal Imbalance: Prolonged fasting or drastic calorie restriction can disrupt hormonal balance in the body. This may result in irregular menstrual cycles in women, reduced testosterone levels in men, and potential fertility issues.

Low Energy Levels: Incorrect IF practices can lead to a lack of energy, reduced concentration, and irritability. These symptoms can hinder daily activities and have adverse effects on overall productivity and mood.

Binge Eating: Following overly restrictive eating windows may increase the risk of binge eating during the feeding periods. This can negate any potential benefits of intermittent fasting and lead to weight gain.

Blood Sugar Issues: For individuals with diabetes or insulin resistance, intermittent fasting may cause fluctuations in blood sugar levels, potentially leading to hypoglycemia or hyperglycemia.

Dehydration: During fasting periods, individuals might forget to drink enough water, leading to dehydration, especially in hot climates or during physical activities.

Unsustainability: Extreme fasting schedules can be difficult to maintain in the long term. People may become discouraged by the restrictions and give up on the approach altogether, leading to potential weight fluctuations and negative effects on metabolism.


Intermittent fasting can be a beneficial dietary approach for those looking to lose weight, improve insulin sensitivity, and enhance brain function. It can also promote longevity and reduce inflammation in the body. 

If done correctly, intermittent fasting can be an effective way to improve your overall health and well-being.

source: Freepik

Improper Intermittent Fasting practices can lead to nutritional deficiencies, muscle loss, disordered eating patterns, hormonal imbalances, low energy levels, and other potential risks. 

Intermittent fasting is not for everyone, and it's essential to consult a doctor before embarking on any significant dietary changes. People who are underweight, pregnant, or have a history of eating disorders should avoid intermittent fasting. Moreover, it's vital to maintain a balanced diet and consume the right amount of nutrients during your eating window to avoid nutrient deficiencies.

Moreover, even if you decide to try out intermittent fasting after consulting your doctor it is vital to ensure that your diet contains all necessary nutrients during your feeding windows in order to avoid nutrient deficiencies over time.

Article Citations & Bibliography

  1. Zhao D. et al. Association of Eating and Sleeping Intervals With Weight Change Over Time: The Daily24 Cohort; Journal of the American Heart Association. 2023;12:e026484
  2. De Cabo R and Mattson MP. Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine. 2019;381(26):2541-2551. doi: 10.1056/NEJMra1905136.
  3., accessed on 22th of July

Please note that the information provided on this blog is for educational and informational purposes only. It is not intended to be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this blog.

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Manuela Băbuș.
Medical Writer