Momentum in the Mountains 2024


What Happens When You Fast and When You Eat

author avatar Dr. Eric Berg 04/23/2024

I used to think fasting was just a fad diet. Boy, was I wrong! Turns out, fasting and ketosis are like the dynamic duo of health - they work together to supercharge your body and mind. And the benefits? They'll blow your mind.

I'm talking weight loss, improved brain function, and even a longer lifespan. Yeah, you read that right. Fasting and ketosis can help you live longer. And the best part? It's not some crazy, complicated process. It's actually pretty simple once you get the hang of it.

So, if you're ready to optimize your health and feel like a brand new person, stick with me. I'm about to spill all the secrets on the incredible benefits of fasting and ketosis.

The Science of Fasting: How It Affects Your Body

Fasting is a powerful tool that can profoundly impact your health and well-being. When you fast, your body undergoes physiological changes that can improve insulin sensitivity, weight loss, and even cellular repair.

In this post, we'll explore the science behind fasting and how it affects your body on a cellular level.

One of the most significant changes that occur during fasting is a shift in your body's energy source. When you eat, your body breaks down carbohydrates into glucose, which is then used for energy.

However, when you fast, your body is forced to find alternative sources of fuel, such as stored fat and ketones.

Understanding Insulin's Role

Insulin is a hormone that plays a crucial role in regulating blood sugar levels. When you eat, your body releases insulin to help transport glucose from your bloodstream into your cells, where it can be used for energy or stored as glycogen.

However, when you consume too many carbohydrates or sugary foods, your body can become resistant to insulin, leading to high blood sugar levels and an increased risk of type 2 diabetes.

The Shift from Glucose to Fat Storage

When you eat more calories than your body needs, the excess glucose is converted into fat and stored in your liver and other tissues. Over time, this can lead to fatty liver disease, which is associated with insulin resistance and an increased risk of heart disease.

During fasting, however, your body is forced to tap into these fat stores for energy, leading to a reduction in liver fat and an improvement in insulin sensitivity. Studies have shown that just 12 to 24 hours of fasting can significantly reduce liver fat and improve insulin sensitivity.

  • When you eat, glucose, amino acids, and fatty acids increase insulin in the blood.

  • Insulin facilitates nutrient entry into cells for energy or storage as glycogen.

  • Glycogen storage leads to water retention, with 3 to 3.8 times the amount of water for each molecule of glycogen.

  • Excess glucose is converted into fat, accumulating in the liver and as ectopic fat.

The Transition to Ketosis During Fasting

As your body depletes its glycogen stores during fasting, it produces ketones from stored fat. Ketones are an alternative fuel source that can be used by your brain and other organs when glucose is not available.

This process, known as ketosis, is a natural adaptation that allowed our ancestors to survive periods of food scarcity. Today, many people intentionally induce ketosis through fasting or a ketogenic diet to improve their health and lose weight.

Glycogen Depletion and Ketone Production

During the first 12 to 24 hours of fasting, your body uses up its glycogen stores and breaks down fat for energy. This process is known as lipolysis, resulting in the production of free fatty acids and glycerol.

As fasting continues, your liver begins to convert these fatty acids into ketones, which your brain and other organs can use for energy. This process is known as ketogenesis, and it typically begins around 12 to 24 hours into a fast.

  • Fasting results in decreased glucose and insulin levels, leading the body to utilize excess glucose and glycogen reserves.

  • After glycogen depletion, about 40% of fat is used for ketone production within 12 to 72 hours.

  • Prolonged fasting leads to adaptation into a state of ketosis, where the body efficiently uses ketones and fat for energy.

Autophagy and Its Health Benefits

In addition to the metabolic benefits of fasting, there is also evidence to suggest that fasting can promote a process known as autophagy. Autophagy is a natural cellular process that involves the breakdown and recycling of damaged proteins and organelles.

During fasting, autophagy is upregulated as a way to conserve energy and recycle nutrients.

This process has been shown to have a number of health benefits, including improved brain function, increased longevity, and a reduced risk of chronic diseases such as cancer and neurodegenerative disorders.

Therapeutic Benefits of Autophagy

One of the most exciting potential benefits of autophagy is its ability to promote cellular repair and regeneration.

Studies have shown that autophagy can help to clear out damaged proteins and organelles, which can accumulate over time and contribute to aging and disease.

In addition, autophagy has been shown to have neuroprotective effects, particularly in the context of neurodegenerative disorders such as Alzheimer's and Parkinson's disease.

By clearing out damaged proteins and promoting the growth of new neurons, autophagy may help to slow the progression of these diseases and improve cognitive function.

  • Certain parts of the body require glucose, which can be produced from fat and ketones during fasting.

  • Fasting promotes autophagy, a process that cleans up damaged proteins and recycles cellular components.

Fasting's Impact on Insulin Resistance and Liver Health

One of the most significant benefits of fasting is its ability to improve insulin sensitivity and reverse insulin resistance.

Insulin resistance is a condition in which your body becomes less responsive to the effects of insulin, leading to high blood sugar levels and an increased risk of type 2 diabetes.

During fasting, your body is forced to rely on stored fat for energy, which can help to reduce the accumulation of fat in your liver. This, in turn, can improve insulin sensitivity and reduce your risk of developing fatty liver disease and other metabolic disorders.

  • Accumulation of fat in the liver can cause insulin resistance and hinder glucose storage as glycogen.

  • Muscle glycogen remains relatively stable during fasting, as the body can produce glycogen from non-carbohydrate sources like fat.

The Role of Potassium in Glycogen Storage

While fasting can be an effective way to improve your health and lose weight, it's important to make sure that you're getting enough nutrients to support your body's needs. One nutrient that is particularly important during fasting is potassium.

Potassium is an essential mineral that plays a key role in regulating fluid balance, nerve function, and muscle contractions. It's also important for the storage of glycogen, which is the primary source of energy for your muscles and liver.

  • Glycogen is a storage form of glucose and requires potassium for storage.

Intermittent fasting illustration

Fast Track to Health

Explore the remarkable advantages of incorporating fasting and achieving ketosis through the 18:6 fasting method. This guide reveals seven unexpected benefits fasting and ketosis can offer for overall health and well-being.

From promoting weight loss and improving metabolic flexibility to enhancing cognitive function and supporting cellular repair, fasting and ketosis can lead to transformative health outcomes.

The 18:6 fasting approach, where individuals fast for 18 hours and consume all their meals within a 6-hour window, facilitates the transition into ketosis and amplifies the benefits of fasting.

By embracing this approach, individuals can unlock the potential of fasting and ketosis to optimize their health and vitality.


Fasting and ketosis are like the secret weapons for optimal health. Together, they're like a magic trio - melting away pounds, making you sharper upstairs, and possibly giving you more time here. Pretty impressive, right?

But here's the thing: it's not just about the physical benefits. Fasting and ketosis can also help you develop mental clarity, emotional resilience, and a newfound appreciation for the food you eat. It's a total game-changer.

Let's face it, taking charge of our health feels great. Fasting and entering ketosis could have incredible benefits. How about kicking things off today? Trust me, your body (and mind) will thank you.

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