The Scientific Effects Of Fasting On The Body

The Scientific Effects Of Fasting On The Body

Fasting is the practice of abstaining from eating food or drinking liquids for a set period of time. It is a powerful tool that today is still widely misunderstood as dangerous, extreme, or simply regarded as a diet fad to lose weight. Despite this, fasting is an amazing mechanism that we can use for healing the body from the inside out, facilitating cellular repair, and even goes hand in hand with deep spiritual practices.

When we eat food, our bodies have to spend energy breaking down and digesting the meal. Depending on the type and quality of food, such as heavy meats or incredibly processed snacks, it can take even more energy for your body to turn that food into the various nutrients that your body then uses for fuel.

However, this means that when our bodies are busy digesting, there is significantly less energy spent on the multitude of other processes and functions that the body normally does, such as cellular repair, turning excess fat into energy, and fighting off disease.

Fasting then (at least on a physical level), allows the body to relax the digestive system and apply 100% of its energy to the rest of the body where needed.

The benefits of fasting are a rather long list of physical benefits, from helping our brains ward off neurological diseases like Alzheimer’s and Parkinson’s, to inducing cellular repair processes, lowering the risk of diabetes, reducing stress and inflammation and even preventing cancer.


When we eat, glucose is stored in our liver as a form of fuel called glycogen. This takes up to 10 – 12 hours to become depleted from our system. Once it’s all used up, our body starts burning fats which are converted into ketones, a natural chemical that our brains use for energy.

Ketones play a vital role in shifting the structure of our neural synapses to promote heightened learning and improve our overall brain health. However, when we are constantly introducing new food into our system, our bodies don’t have the chance to deplete the glycogen in our liver and, thus, ketones aren’t able to be produced.

Mark Mattson, a professor of Neuroscience at the John Hopkins School of Medicine has conducted numerous studies showing the benefits of intermittent fasting.

His experiments showed that limiting your caloric intake for two days a week can drastically improve neural connections in the hippocampus – a part of the brain which regulates long and short-term memories.


In the BBC documentary Eat, Fast & Live Longer, television journalist Michael Mosley sets out to experience the benefits of fasting himself. One of the most prominent factors he learns about is the growth hormone called IGF-1. This stands for the insulin-like growth factor. It is a hormone within us that keeps us in “go” mode and is important for when we are children growing up, allowing us to grow taller and increase our body sizes where necessary.

However, later in life, we don’t need to grow so big, and normally IGF-1 levels drop significantly. If the levels are too high, they are often responsible for fuelling tumor growth and other forms of cancer or disease. When the IGF-1 hormone levels are too high, are bodies are kept in a state of growth mode, rather than repair mode. These IGF-1 levels can raise beyond normal levels when we eat animal foods, as many studies have found high IGF-1 levels linked to proteins from milk, seafood, red and white meat, and other foods with high amounts of saturated fat.

To reduce IGF-1 levels, there are several actions we can take. Besides omitting these types of foods from our diet, studies have also found that we can rapidly reduce IGF-1 levels to a normal state with a short 3-day water fast. Upon these levels dropping, a number of repair genes are activated and begin to heal the body from the inside.

Read Fasting Upto 72 Hours Can Reboot The Entire Immune System: New Study Reveals

You can watch Michael’s entire journey and transformation here.

A scientist named Valter Longo, featured in the BBC documentary above, is a Gerontological researcher at The University of Southern California. He and his colleagues have shown that fasting eases side effects of chemotherapy, and promotes health advantages to the body. His team found that reducing the amount of food in middle-aged mice for two 4-day periods each month actually allowed those mice to outlive their peers by about 3 months.

They also saw that those mice were 45% less likely to develop cancer and their insulin levels were 90% lower. These mice were still able to retain their mental ability and beat the control animals in two kinds of memory tests.

In another study, short-term fasting was as effective as chemotherapeutic agents in delaying the progression of tumors in mice. This study concluded, “That multiple cycles of fasting promote differential stress sensitization in a wide range of tumors and could potentially replace or augment the efficacy of certain chemotherapy drugs in the treatment of various cancers.”

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