A little starvation can really do more for the average sick man than can the best medicine and the best doctors.

-Mark Twain

Intermittent or time restricting eating simply means periods of eating and periods of not eating. Fasting has been a natural part of human history for thousands of years and current research is now showing the science behind how fasting can be used as a therapeutic treatment in obesity, diabetes, autoimmune disease, cancer and Alzheimer’s disease. We are realizing the timing and frequency of meals is as important as the composition of meals. Determining when to eat is as important as what to eat.

Is it really that simple? Can the introduction of fasting or time restricted eating alone have significant health benefits?

Yes! Intermittent fasting or time restricted eating anywhere from 12 hours to a few days can have significant effects on your health. Research shows multiple benefits of fasting including weight loss, decreased blood sugar levels, improved insulin sensitivity, improved fat-burning, reduction in cholesterol levels, lowered blood pressure, prevention of neurodegenerative diseases such as Alzheimer’s disease, reversal of aging processes, enhanced mental clarity and concentration, improved immune function, and decreased inflammatory markers. If the health benefits were not enough consider the other advantages it is the simplest dietary change you can make, it saves both time and money, it is both practical and flexible, it can be used with any other diet and it works! Fasting is profoundly simple and yet simply profound.

Fasting is the oldest dietary intervention in the world. It is profoundly different from all other dietary strategies. It is not the latest and greatest but the tried and true. It is not something to do but something to not do.

-Jason Fung

How does it work?

The body has two modes the fed state and the fasted state. Our bodies are either storing food energy or burning food energy. If the fed state and fasted states are balanced there is no net weight gain, hormone levels are balanced, and metabolism is working efficiently.

During a fed state insulin levels increase; insulin is a hormone involved in the storage and use of food energy. Insulin helps glucose into cells to be used as energy, excess glucose can then be stored in the liver as glycogen. There is a limit to the amount of glycogen that can be stored and once that limit is reached the body will turn excess glucose into fat. This fat can be stored in the liver or deposited in the body and as we know there is no limit to the amount of fat produced and stored. During a fasting state these processes are reversed. Insulin levels decrease, signaling the body to start using stored energy. First the body will use easily assessable glycogen stores from the liver, when glycogen stores are depleted the body will start to use stored body fat for energy.  During fasting the body switches from burning glucose for energy to burning fat for energy improving insulin sensitivity resulting in all of the health benefits listed above.

How does fasting increase stem cell production?

Research has shown during periodic fasting there is an elevation of circulating stem cells in the blood. Our bodies cellular components are constantly shifting between degeneration and repair. Elevation and activation of stem cells promotes regenerative processes in the immune, nervous and musculoskeletal systems. Fasting states also promote clean up and processing of damaged cells and damaged components inside the cells, which allows for replacement with newly regenerated cells from activated stem cells. During fasting states, there is an increase in DNA based repair mechanisms, a decrease in oxidative stress, and reduction in inflammation promoting neurogenesis and mitochondrial biogenesis leading to better functioning in all organ systems.

What is the Difference between intermittent fasting and calorie restriction?

It has long been recommended to lose weight simply just eat less and move more. Unfortunately, this advice has not been effective for weight loss or reversing insulin resistance proving not to have the same health benefits as fasting. This is explained by the beneficial hormonal change in insulin, adrenaline, and growth hormone that happen during fasting that are not achieved in caloric restriction. Another difference is that during consistent caloric restriction the body adapts to decreased fuel by slowing metabolism and energy expenditure. During intermittent fasting metabolism stabilizes and often increases while blood sugar and insulin levels go down and growth hormone increases.

How long do I fast?


12 hours of fasting and a 12-hour eating window. This would look like eating breakfast at 7am lunch mid-day and finishing dinner by 7pm. Though this seems simple most Americans actually do not go 12 hours without eating. Even a 12 hour fast can have insulin balancing effects and be a great preventative measure for diabetes, cardiovascular and neurodegenerative disease. This strategy however, may not be powerful enough to reverse weight gain or other metabolic disease.


14 hours of fasting and 10-hour eating window. This would look like eating your first meal at 9am and finishing eating at 7pm or your first meal at 7am and your last meal at 5pm. On this schedule, it is simple to still have three meals within the 10-hour eating window. When it comes to regulating insulin, it is not about the amount you eat it is about the amount of time spent in the fed state and the fasting state.


16 hours of fasting and an 8-hour eating window. This would look like your first meal at 11am and finishing your last meal by 7pm. This is a very popular method because it is so easy to incorporate into daily life. You can make a choice to eat 2 or 3 meals within the eating window. Research shows based on circadian rhythms the largest meal should be mid-day between noon and 3pm and smaller meals later in the eating window.


20 hour fast each day and a 4-hour eating window. This looks like one meal per day.

This meal for many reasons is often easier to eat in the evening, but trying to eat earlier in the evening or later afternoon is best. As with all fasting it is important to consume nutrient dense, plant based, unprocessed foods. Meals should consist mostly of vegetables with complex carbohydrates, healthy fats and moderate protein.


This approach consists of 5 days of normal eating with 2 days of extreme caloric restriction of 500-600 calories. On the two days of caloric restriction the calories are kept low enough that there is the same beneficial hormonal adaptations as fasting. This can also be achieved by doing a 24-hour fast two days a week. That would look like eating one meal at 7am and waiting until 7am the following day to eat again or eating one meal at 7pm and waiting until 7pm to eat again.

Multi day fast

Daily intermittent fasting has many health benefits including the prevention of insulin resistance, reversing minor insulin resistance, decreasing inflammation, and helping with weight loss. The most prevalent shifts in the reversal of degenerative and metabolic disease along with stimulating the production of stem cells comes from longer periods of fasting.

Extended fasting lasting 48–120 hours activates pathways that enhance cellular resistance to toxins and stress. The physiological and hormonal changes caused by extended fasting are much more pronounced than those caused by calorie restriction or overnight fast, in part because of the requirement to fully switch to using fat and ketones for energy metabolism after glycogen stores are depleted.

“The best of all medicines is resting and fasting.”

-Benjamin Franklin

Please check with a health care provider before starting any fasting regime. There are medications and conditions that fasting may not be advantageous or may need close monitoring.