Intermittent fasting is term coined by the research world that refers to an extended duration of minimal calorie intake. Believe it or not, humans are evolutionarily adapted to performing intermittent fasts – our ancestors performed extended fasts whenever food was unavailable, and feasted only when they could procure enough food to eat.
However, in our modern world of abundance, deliberately fasting for an extended period of time is anything but “normal.”
Fasting goes against every morsel of modern life, and is in direct opposition to the abundance-based food culture that we have worked so hard to create. In our world of fast food, on-demand food delivery and 24-hour convenience stores, choosing not to eat food can seem strange indeed.
I spent my entire graduate career investigating the effects of intermittent fasting in rodents, in order to understand why calorie restriction and intermittent fasting are the gold standards for improving insulin sensitivity. As a result of this active body of research, tens of thousands of people across the world engage in intermittent fasting on a weekly basis, as a means of improving their body composition, losing fat mass, shedding pounds or observing a religious holiday.
The research world has taken a large interest in calorie restriction and intermittent fasting, for the explicit purpose of identifying cellular mechanisms that may retard the aging process and promote excellent metabolic health. And in the process of studying intermittent fasting, researchers have uncovered a laundry list of health benefits that confuse even the most educated professors.
The Metabolic Benefits of Intermittent Fasting
There is only one way to increase your lifespan: reduce your calorie intake.
Restrict your calorie intake by 25%, and you may add years to your life. Simply stated, there is no pill you can take, no amount of exercise you can perform, and no food you can eat that can actually make you live longer (1–9). All you have to do is reduce your food intake, and watch as your longevity actually increases.
How does this work? It turns out that restricting your calorie intake delays the onset of many age-related diseases, including heart disease, diabetes, hypertension and cancer. Over 75 years of research has uncovered some amazing benefits of calorie restriction and intermittent fasting, and the results are summarized below:
- Reduced LDL (the bad cholesterol) (10,11)
- Increased HDL cholesterol (the good cholesterol)
- Reduced triglycerides
- Reduced blood pressure
- Reduced inflammation
- Reduced cancer risk (tumor growth and progression) (12)
- Increased fat burning and fat loss
- Improved body composition
Improved Insulin Sensitivity
As far as glucose metabolism is concerned, intermittent fasting is an absolute goldmine. Intermittent fasting is an incredibly powerful tool for normalizing glucose and improving glucose variability. Apart from exercise, intermittent fasting is the most powerful natural insulin sensitizer known to man.
The specific effects of intermittent fasting on diabetes are listed here (13–24):
- Reduced fasting blood glucose
- Reduced post-prandial (after meal) blood glucose
- Reduced glucose variability
- Increased insulin sensitivity
On a molecular level, why does intermittent fasting improve insulin sensitivity? Our current understanding filters down to the following critically important puzzle pieces:
Enhanced Fat Clearance in Muscle and Liver
Insulin resistance is defined as the accumulation in tissues that are not designed to store fat (mainly the muscle and liver).
When you restrict intake of all carbohydrates, fat and protein, tissues all across your body have no choice but to burn their stored onboard fuel for energy. When you fast for an extended period of time, the fat deposits that have accumulated over time become the fuel that cells need to operate. As a result, the size of the excess fat droplet gets smaller over time.
Interestingly, as the size of the lipid droplet in muscle and liver cells decreases, those cells become more responsive to insulin. In other words, by reducing the size of the fat droplet, insulin becomes more powerful (13-24).
Clearance of Oxidized Cholesterol Deposits in Blood Vessels
There is no doubt that the elasticity of your vasculature is as important as the health of body tissues. Given that glucose and insulin circulate in the blood, the easier they can cross the walls of blood vessels the more infrequent high blood sugars become.
Lipid deposits accumulate on the inside wall of blood vessels with age, and over time these lipid and cholesterol deposits become oxidized. Oxidized deposits harden and form blood clots, occluding blood vessels, increasing blood pressure, hardening vessel walls and increasing the risk for a heart attack.
Studies have shown that calorie restriction and intermittent fasting are both extremely beneficial for reducing these vascular consequences of aging, resulting in reduced LDL cholesterol, increased HDL, reduced arterial blockage, reduced blood pressure and improved transport of glucose and insulin across the vessel walls.
Take Home Message
Think of intermittent fasting as your one-stop-shop for attaining excellent vascular health, for reducing cholesterol, reducing blood pressure, and preventing against vascular complications in the long term. A metabolic triple whammy indeed.
In the next article in this series, stay tuned for details on how to perform a simple and highly effective weekly intermittent fast. For now, ask yourself one question: do you want less fat? If so, intermittent fasting is for you.
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