What Is Intermittent Fasting and Should You Try It?

Intermittent fasting has recently become a very popular dieting concept and for good reason: research and studies have proven this method to work. Benefits of intermittent fasting range from weight loss to reduced oxidative stress to preserved learning and memory functioning.

The problem is, however, that while this trend, like many other diet and exercise trends, originated from legitimate science, the facts tend to be distorted by the time they reach mainstream popularity. Benefits are exaggerated, risks are downplayed, and science takes a back seat to marketing. The goal of this post is to give you the facts and science behind intermittent fasting to help you decide if this dieting concept could help you to achieve your goals.

What is intermittent fasting?

Fasting has been practiced for thousands of years, but only recently has fasting been studied for potential health benefits. Traditional fasting involves ingesting no or minimal amounts of food and caloric beverages for periods that typically range from 12 hours to three weeks. (Cell Metab., 2014)

Intermittent fasting involves a period of severe calorie restriction (ranging from 0-25 percent of a normal daily caloric intake) that typically ranges from 16 to 24 hours. The restrictive phase is then followed by a relatively normal calorie intake for a period of 8 to 24 hours. According to bodybuilding.com, the central idea behind the implementation of intermittent fasting is to reduce overall calorie consumption, ideally resulting in weight loss.

There are many different intermittent fasting protocols which vary in lengths for the fasting period as well as the suggested calorie intake. Below are a few examples of intermittent fasting plans:

• The 8-hour Abs Diet by Melissa McAllister: This plan has you eat all of your food within an 8 hour window each day, which means daily fasting for 16 hours.

• The Alternate Day Diet by James Johnson, M.D.: Also known as the UpDayDownDay Diet®, this intermittent fasting protocol follows a 24-hour rotation of low-calorie intake and normal-calorie intake. Studies in mice have demonstrated that the alternating days of caloric intake help to activate the SIRT1 gene, which assists with weight loss by inhibiting fat storage and increasing fat metabolism.

• The Warrior Diet by Ori Hofmekler: As described by the author, this intermittent fasting plan pairs a 20-hour fast with a 4-hour feeding window. The goal of the fast is to increase the actions of the Sympathetic Nervous System (your fight-or-flight response) which may help to stimulate lipolysis (fat breakdown) and increase metabolic rate. The feeding window is used to increase the activity of the Parasympathetic Nervous System (the rest-and-digest system), which will help increase the absorption of glucose and assist with recovery.

Does science support the intermittent fasting trend?

There is in fact a large body of research to support the health benefits of intermittent fasting, though most of it has been conducted on animals, not humans. (CMAJ. 2013) Regardless, the results have revealed many beneficial outcomes of intermittent fasting, including:

• Improve biomarkers of disease
• Reduce oxidative stress
• Reduce inflammation
• Optimize energy metabolism
• Preserve learning and memory functioning
• Promote potent changes in metabolic pathways and cellular processes such as stress resistance, lipolysis, and autophagy

Intermittent fasting and weight loss

The way that intermittent fasting can help you to lose weight and burn fat is based on the body’s switch to a metabolic mode called ketogenesis. In a fed state, the human body uses insulin to bring glucose from the food you consume into the cells for use as energy. Periods of 12 to 24 hours of fasting will typically result in a 20% or greater decrease in the blood glucose level, which in turn lowers insulin release. The result is ketogenesis, an increase in fatty acid oxidation, which means that the body is now using stored fat as its energy source.

How intermittent fasting relates to exercise

According to Mark Mattson, senior investigator for the National Institute on Aging, there are several theories about why fasting provides physiological benefits. “The one that we’ve studied a lot, and designed experiments to test, is the hypothesis that during the fasting period, cells are under a mild stress,” he says. “And they respond to the stress adaptively by enhancing their ability to cope with stress and, maybe, to resist disease.”

The word “stress” often has negative connotations, but certain areas of the body can benefit from mild stress. Consider a really tough workout. Both your muscles and your cardiovascular system undergo stress, right? Weight training will cause micro-tears in the muscles being trained, which will result in muscle growth after they have repaired. As long as you give your body time to recover, it will grow stronger. “There is considerable similarity between how cells respond to the stress of exercise and how cells respond to intermittent fasting,” says Mattson. (CMAJ. 2013)

Should you try intermittent fasting?

If there is one key takeaway point from this whole article, it’s this: don’t believe every dieting trend that’s out there, even if it’s the most popular! Always look at the science and facts behind why a diet or nutritional concept works. Intermittent fasting is a prime example of a trend taking off without most people understanding the facts behind it.

Plus, the majority of studies done on intermittent fasting have been completed on animals, not humans. The benefits found in animal studies cannot be generalized to the human population without further research.

So should you try intermittent fasting? Of course, that decision can only be made by you. Consider the science behind this dieting concept and as always do what feels right for your body.

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