Hem » Articles » Health » Intermittent Fasting – the Basics

The quote “Let food be thy medicine and let thy medicine be food” from the Greek physician Hippocrates in 440 BCE holds true today, as we now know that altering food consumption can be used as an intervention to improve health and wellness and improve health span and promote longevity. This idea has been supported by research across different species, but there is still a lot of debate on the ideal diet for optimal health.

Intermittent fasting (IF) has gained popularity in recent years due to its potential health benefits, such as weight loss, improved metabolic health, and longevity. In this 3-part series, we’re going to take a closer look at IF, covering topics like what IF is and how it works, its effectiveness for weight loss, and other potential benefits.

Keep reading if you want to learn more about this popular type of diet.


What is intermittent fasting?

IF alternate periods of eating with periods of fasting (or limited caloric intake) (1).

Most diets in the past have focused on what and how much one eats, but not when one eats. Over the past decade, IF has become a popular approach for weight loss and improving overall health (2). Calorie restriction (CR), which involves reducing caloric intake without malnutrition, has been found to promote healthy lifespan and weight loss in various species, including nonhuman primates (2). In overweight humans, short-term CR can improve cardiovascular risk factors, insulin sensitivity, and mitochondrial function (2).

However, long-term daily CR can be challenging for most people to sustain. This is where IF comes in as an alternative approach. Studies have shown that IF can deliver similar benefits as continuous CR, such as weight loss and improvements in cardiometabolic health. It has become a promising dietary strategy for those looking to improve their health without having to continuously restrict their calories every day. Some people prefer IF due to its simplicity- they only need to monitor the time they eat instead of counting calories.


Different types of intermittent fasting methods:

There are different variations of fasting that have been studied, with the most popular ones being time restricted eating, alternate day fasting, the 5:2 diet, and periodic fasting (1).


Time restricted eating

The time restricted eating is a popular variation of IF where individuals consume food only in 6–8-hour window every day. A popular IF schedule is 16/8 where the individual fasts for 16 h and eats as normal for 8 h.

Alternate day fasting

The alternate day fasting consist of alternating between a fasting day and a normal eating day. During the fasting day either no food and caloric beverages are consumed, or 20-30 % of the normal caloric intake (reduced caloric intake) is consumed.

5:2 diet

The 5:2 diet consists of eating 5 days a week normally and fasting (or reduced caloric intake) for 2 (consecutive or non-consecutive) days a week.

Periodic fasting

Another form of fasting is called periodic fasting during which individuals fast for 2-7 days in a month.


In conclusion, IF is a flexible approach to weight loss and improved health with various options to suit different lifestyles and goals.


How does intermittent fasting work?

Scientists aim to gain a better understanding of the mechanisms underlying the health benefits of IF, with a particular emphasis on the metabolic alterations, gene regulation, and cellular processes involved. According to researchers IF works by shifting the body’s primary fuel source from glucose to stored fat, which can result in weight loss (2). Fasting also stimulates autophagy, a process where the body breaks down and recycles damaged cells, which can help reduce inflammation and improve cellular function (2).

After studying the molecular mechanisms of IF, scientists have found that it can induce modifications in gene expression, metabolic pathways, and epigenetic alterations ((https://nem.health/en/epigenetics-dna-methylation-and-aging/ ) that help enhance cellular health and promote longevity. There is also evidence to suggest that IF can improve brain function and decrease the likelihood of developing neurodegenerative disorders (3).

More research is needed to fully understand the mechanisms behind these effects and to determine the optimal fasting regimen for different individuals. Additionally, although IF is a simple and flexible approach to dieting, focusing on the time of eating instead on the calorie intake, it is still recommended to make smart choices and to eat nutritious diet. Finally, IF has health benefits, but it’s not suitable for everyone. People with diabetes, eating disorders, and pregnant or breastfeeding women should consult their healthcare provider before trying IF. It’s important to discuss any dietary changes with a healthcare professional to ensure they’re safe and appropriate for one’s health needs.

Read more about intermittent fasting:

The effectiveness of intermittent fasting

Health benefits of intermittent fasting beyond weight loss


Silviya Demerzhan, Ph.D.

Chief Scientific Officer, Nordic Executive Medicine
Medical review by: Dr. Mahir Vazda MD


  1. Elortegui Pascual P, Rolands MR, Eldridge AL, Kassis A, Mainardi F, Lê KA, et al. A meta-analysis comparing the effectiveness of alternate day fasting, the 5:2 diet, and time-restricted eating for weight loss. Obesity. 2023;31(S1):9–21.
  2. Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous III AG, et al. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity. 2018;26(2):254–68.
  3. Longo VD, Mattson MP. Fasting: Molecular Mechanisms and Clinical Applications. Cell Metab. 2014 Feb 4;19(2):181–92.