The Science Behind Intermittent Fasting

January 6, 2023

The concept of fasting dates back to the time when medicine was developing, and Hippocrates was the pioneer of the field. The 'father of Medicine, Hippocrates, through a far-fetched scientific outlook and advocating rational thinking, manoeuvred modern medicine(1). He recommended the concept of fasting to people displaying particular health conditions and gained popularity soon after. 

The unforgotten concept of fasting has been modified from the 5th century to be based on the type of health condition developed. One such kind of fasting is the Intermittent fast or the 5:2 diet (people eat what they want for 5 days a week and limit calories on the other 2 days). The 5:2 diet gained popularity after Dr. Michael Mosley's documentary based on his close friend Valter Longo's research. It is also mentioned in his bestselling book ‘The Longevity Diet’, which talks about how to maximize your healthy lifespan through a planned everyday diet(2)

What is Intermittent Fasting Anyway?

Intermittent fasting (IF) is an intersectional strategy where individuals are subjected to shifting periods of fasting. It doesn't specify what food to consume but focuses more on when you should eat them. Intermittent Fasting revolves around eating patterns between fasting and eating(3).

It aids in weight loss, increases mental capacity, and decreases the incidence of Insulin Resistance (diabetes), heart problems and cancer. Check out to read more about the benefits of IF.

The science behind IF is even more interesting.

The Science Behind IF

Intermittent fasting refers to eating plans that alternate between fasting and eating periods. The goal is to starve the body long enough to trigger fat burning systematically. The body does not have access to the usual glucose when we fast which stimulates the body to search for other means of producing its own energy. Thus, the body begins gluconeogenesis (wherein the body produces its own sugar). In this procedure, the liver plays an important role in converting non-carbohydrate materials like fats, amino acids and lactate into glucose energy (4). When done correctly, there is evidence that it can help lose weight, lower blood pressure and cholesterol, prevent or control diabetes, and improve the brain's health. (5)(6).

During a meal, carbohydrates in food are broken down into glucose, which is transported to various organs and serves as the major energy source. The unused or excess glucose is stored for later use in the liver and adipose tissue in the form of glycogen and fats. Between meals, the liver converts glycogen back to glucose to supply the body with energy.

An inactive person takes about 10 to 12 hours to use up the glycogen stores, although someone who exercises may do so in much less time. 

Once the glycogen reserve in the liver is depleted, the body taps into energy stores in fatty tissues. This is when fats are broken down into free fatty acids, which are then converted into additional metabolic fuel.

Insulin is the hormone required for driving glucose into cells. Insulin level is regulated to match the amount of glucose in the blood, high after a meal and low between meals. Constant high insulin levels may de-sensitize body tissues, causing insulin insensitivity- the hallmark of prediabetes and type 2 diabetes.

Advantages: Fasting helps keep insulin levels low, reducing diabetes risks. Fasting also benefits the brain - it challenges the brain like physical exercise does. It promotes the production of neurotrophic factors, which support the growth and survival of neurons. 

Disadvantage: But fasting is not for everyone - pregnant or breastfeeding women, people with eating disorders, or those with advanced diabetes type 1 are some who should not attempt fasting.

There are several approaches to intermittent fasting, but the easiest to achieve is perhaps to extend the usual nighttime fast. A daily cycle of a 16-hour fast followed by an 8-hour eating window is usually sustainable.

It is important to stay hydrated and know your physical limits; the fast must be broken slowly. Overeating after fasting, especially unhealthy foods, must be avoided. (7).


  2. "BBC Two - Horizon, 2012-2013, Eat, Fast and Live Longer". BBC
  3. Dong TA, Sandesara PB, Dhindsa DS, et al. Intermittent Fasting: A Heart Healthy Dietary Pattern?. Am J Med. 2020;133(8):901-907. doi:10.1016/j.amjmed.2020.03.030 
  4. Puckett, S. (2020, January 20). Fasting for Your Health: What You Need to Know. Boulder Medical Center.
  6. Trueland J (December 2013). "Fast and effective?". Nursing Standard. 28 (16–18): 26–7. doi:10.7748/ns2013. 
  7. Intermittent fasting. Alila Medical Media. 

Chandra Biswas

She is specialized in Cell and Molecular biology and is an enthusiastic researcher. She believes in sharing practices which are scientifically researched and proven.

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