Fasting and Your Body: The Evidence-Based Health Benefits

Did you know that our ancestors were fasting unintentionally and didn't follow the modern routine of eating three large meals daily, snacking frequently, or living a sedentary lifestyle? 

Yet, they adapted and developed creativity, imagination, and problem-solving skills. They invented tools, planned hunts, and communicated effectively, which helped them survive and evolve.

Additionally, fasting has long been considered a spiritual practice in many religions, including Zoroastrianism, Christianity, Judaism, and Islam. 

Just like our ancestors adapted to periods of food scarcity, today, fasting has become a modern tool for improving health and longevity. Researchers have shown that it can positively impact metabolism, weight management, and overall health.

The four main types of fasting are intermittent, prolonged, religious, and Fasting-Mimicking Diet (FMD), each serving a unique purpose. Intermittent fasting is widely used for weight loss and fat metabolism. In contrast, prolonged fasting supports deep cellular repair and may lower the risk of chronic diseases.

This blog will explore how fasting affects metabolism and hormones and its potential benefits for managing type 2 diabetes.

How Fasting Affects the Body

• Cellular Repair & Autophagy: 

Autophagy is a cellular process where specific cells in your body degrade and recycle many cellular components for many purposes. One key function is to provide energy, particularly during fasting, as your body lacks fuel.  

Thankfully, fasting triggers the autophagy process, which has benefits, including degrading and recycling old cellular components, providing energy and bulging blocks for many components, and eliminating damaged proteins and harmful substances, especially with aging(Nobel Prize in Physiology or Medicine 2016, n.d.).

• Metabolism Boost & Fat Loss: 

Glucose and fat are the primary sources of energy. After a meal, glucose is immediately used to produce energy, while fat is stored in the body's cells. However, during fasting, the body uses the stored fat to provide energy. 

Fat has many benefits: It is an alternative way of producing energy, provides high energy, and reduces carbon dioxide production from glucose use. 

Additionally, it produces ketone bodies, which are regulatory molecules that enhance organ function, systemic metabolism, and brain health. 

Sintesite also shows that cells create an adaptive response during fasting. This response improves their ability to fight against harmful substances, DNA repair, protein quality control, and the autophagy process. 

Moreover, fasting helps regulate glucose, increases cell stress resistance, and suppresses inflammation. The latter two mechanisms occur because the cells activate pathways that enhance their intrinsic defense against harmful agents(De Cabo & Mattson, 2019). 

• Hormonal Changes:

Fasting decreases insulin and leptin while increasing glucagon, ghrelin, and growth hormone. These changes stimulate the body to use fat and stored sources to produce energy, regulate glucose, improve insulin function, maintain muscle mass, and regulate hunger sensation. 

Here are the most common changes in some hormones:

1. Insulin:

During fasting, insulin decreases due to a decrease in glucose, which stimulates the body to digest fat to produce energy(Karimi et al., 2024).

2. Glucagon:

The hormone increases with lower insulin and blood sugar levels. It sends signals to the liver to break down glycogen, the stored form of glucose, to maintain the energy supply(Karimi et al., 2024).

3. Leptin:

Fat cells release this hormone to regulate hunger sensation and energy consumption. During fasting, leptin decreases, which means low energy stores. Thus, your brain increases hunger sensation and reduces energy consumption(Fekete et al., 2006). 

4. Ghrelin:

The hunger hormone is released from your stomach to tell your brain that you need food when it's empty. Its primary function is to enhance hunger sensations and regulate energy levels(Akalu et al., 2020).

5. Cortisol:

Cortisol is a hormone that increases during stress, such as when fasting. This rise in cortisol helps release energy from the body's stores. However, if cortisol levels stay high for too long, it can lead to problems like muscle loss and a weak immune system(Karimi et al., 2024).

6. Thyroid Hormones:

The thyroid gland produces thyroid hormones to regulate body metabolism. They usually increase the use of energy by cells to improve body temperature and overall energy level. During fasting, the body decreases thyroid hormones to preserve energy levels(Martinez & Ortiz, 2017). 

7. Growth Hormone:

Fasting increases the production of growth hormone (GH). Higher GH levels during fasting help the body use fat for energy and keep muscles healthy. They also help maintain blood sugar levels when you aren't eating(Kim et al., 2021).

8. Asprosin:

Asprosin is a hormone that the body releases when fasting. It tells the liver to put glucose into the bloodstream, providing a steady energy supply. Asprosin may also affect how the body regulates appetite by communicating with your brain(Wenger et al., 2016).

Effect of Fasting on Diabetes

Regarding diabetes, fasting could come with an adverse effect in type 1 diabetes due to the risk of hypoglycemia. 

In type 2 diabetes, fasting shows a promising effect as follows: 

In type 2 diabetes, patients suffer from insulin resistance, which decreases insulin function. Insulin regulates glucose levels and is essential in DNA formation and cell growth(Kahn, 1985). 

Fasting reduces insulin resistance by decreasing caloric intake, which results in decreased insulin secretion and induces the use of fat as a fuel for energy production(Burkewitz et al., 2016). 

Additionally, fasting can favorably influence adipokines, the hormones released by fat tissue:

• Leptin:

Fasting lowers leptin levels due to reduced fat mass and improved leptin sensitivity. In type 2 diabetes, where leptin resistance exists, lowering leptin may help reset appetite and energy expenditure pathways(Albosta & Bakke, 2021).

• Adiponectin:

Fasting and weight loss typically boost adiponectin levels, enhance insulin sensitivity, and provide anti-inflammatory benefits, which are crucial for managing blood glucose in type 2 diabetes(Albosta & Bakke, 2021).

Overall, fasting helps lower insulin resistance, stabilize blood sugar, reduce inflammation, and promote weight loss—all of which improve diabetes management and overall metabolic health. 

However, implementing fasting could be challenging, as you usually eat around three meals plus snacks per day. But you can start gradually, for example, fasting overnight for 8 hours, then gradually increasing it. 

Unlocking the Power of Fasting

Fasting is more than just a dietary trend—it's a scientifically backed approach that enhances metabolism, regulates hormones, and supports long-term health. From cellular repair through autophagy to fat-burning and hormonal balance, fasting triggers robust biological processes that optimize energy use and resilience.

For individuals with type 2 diabetes, fasting shows promising potential in reducing insulin resistance, stabilizing blood sugar levels, and improving metabolic function. 

However, like any lifestyle change, fasting should be approached gradually and tailored to individual needs.

While modern habits revolve around frequent meals, our bodies are designed to thrive in fasting states, just as our ancestors did. Whether you want to improve health, manage weight, or boost cognitive function, fasting offers a natural and effective tool to achieve these goals.

So, if you're considering fasting, start slowly, listen to your body, and embrace the transformation—because sometimes, less truly is more. 

Assessed and Endorsed by the MedReport Medical Review Board