By Dr. Janet Brill

Metabolic Effects of Intermittent Fasting

Intermittent fasting is an umbrella term for various meal timing schedules that cycle between fasting and eating over a given period of time. Methods of intermittent fasting include the popular 16:8 plan (daily time-restricted feeding), alternate-day fasting, the Warrior plan, and the 5:2 plan.

What is the science behind and the metabolic effects of intermittent fasting? Here is a description of what occurs metabolically during the “fasted state.” After a period of approximately 12 hours without consuming calories, the body enters into the fasted state and undergoes the “metabolic switch.” The metabolic switch occurs when the body’s stores of blood sugar are depleted, and the body is forced to dip into fat stores for energy (an increase in lipolysis or fat burning). Here your body flips from the “fed state” to the “fasted state.” Fat in fat cells is broken down and released into the bloodstream. Fat in the form of free fatty acids (FFAs) circulates to the liver where the liver metabolizes the fat and produces ketones. Ketones are released from the liver into the blood where they circulate, taken up by various cells to be used for energy.

Fasting is evolutionarily embedded within our physiology, triggering several essential metabolic functions. Flipping the metabolic switch from a fed to a fasted state does more than helping us lose weight and body fat. Intermittent fasting improves metabolism, lowers blood sugar; reduces inflammation (this improves a range of health issues from arthritic pain to asthma); and even helps clear out toxins and damaged cells (an anti-aging process called autophagy), which lowers the risk for cancer. A decrease in the release of a hormone called IGF-1 is also related to anti-aging and disease prevention.

In the brain, uptake of ketones triggers the release of an important protein called brain-derived neurotrophic factor ( BDNF). BDNF is like fertilizer for brain cells. It helps build and strengthen the cells in areas of the brain responsible for learning and memory. This explains why a boost in ketone production has been shown to improve memory in people with early signs of dementia and other neurodegenerative diseases.

Fasting also increases the release of norepinephrine, a fight or flight hormone that raises metabolic rate, resulting in an increase in metabolism and subsequently aids in weight and body fat loss.

New and exciting research is coming out daily showing that a program of intermittent fasting if followed correctly, is a very reasonable, effective, and sustainable lifestyle for promoting positive metabolic changes in the body conducive to disease prevention and longevity. The key is to combine your intermittent fast of choice with a sensible, plant-based, Mediterranean diet and daily exercise—the trifecta of healthy lifestyle regimens.

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