By Rebecca Rullo, a Nutrition Communication student at Arizona State University
Periodic fasting has been around throughout history but has evolved into several types of fasting today. Ever since studies on animals have shown that restricted calorie intakes may reduce disease risk and lengthen life, researchers have been studying the effects of fasting in humans. Intermittent fasting, particularly, has caught the attention of healthcare practitioners and people wanting to lose weight. And, of course, the major religions of the world have incorporated fasting into their faith practices for centuries.
Today, fasting is associated with many benefits and risks, indicating that some types of fasting may be part of a healthy lifestyle for some individuals.
The Skinny on Fasting
Fasting can vary in length and frequency, from several days or one day, to once a month or several days in a month. Some foods or all foods may be excluded, or one meal or several meals. In two studies from the American College of Cardiology, the test groups fasted one day every month and results showed that those who fasted had lowered risk of heart disease (Warren, 2011). The fasts in this study were infrequent and short-term since they were just one day every month. Besides lowering heart disease risk, several other physical and mental health benefits have been demonstrated by various studies (listed below), including:
- Improved cardiovascular system and immune system
- Improved insulin sensitivity
- Hormone regulation
- Decreased appetite and cravings
- Focus, calmness, and clarity of mind
- Lowered depression and anxiety
However, fasting can also produce negative effects on mood and physical functioning, such as:
- Raised stress hormone levels
- Low blood glucose leading to fatigue
- Poor concentration
- Starvation mode – ketosis
- Dehydration and malnutrition
- Weakened bones and muscles
- Mood swings
Some of these negative side effects, such as starvation mode, malnutrition, infertility, and weakened bones and muscles result from long-term or frequent fasting, after not consuming any food for several consecutive days or weeks. In this case, the negative effects begin after a length of time and grow worse from that point on. Starvation and eating-disorder studies show that deprivation can slow metabolism, causing the body to store fat and triggering a restrict and binge cycle (Whiteman, 2015). This is why skipping meals, starving to lose weight, and dieting are all unhealthy ways to lose weight and why some experts are concerned about fasting leading to disordered eating.
On the other hand, mood swings raised stress hormone levels, and poor concentration are negative effects that are intense at first but subside over time. Typically these result from short-term fasts or infrequent fasts. Because intermittent fasting falls between short and long-term fasting and infrequent and frequent fasting, some overlap of negative effects between the categories is possible. Alternating creates a long-term cycle of short-term fasting and any negative effects usually dissipate after a few weeks of beginning the cycle.
Some experts believe intermittent fasting is a healthy and effective way to lose weight. One expert quoted in Women’s Health Magazine states that since the fasting periods are just every other day and eating is unrestricted on the other days, the problems of dieting can be avoided (Monson, 2014). Other experts feel that intermittent fasting is too similar to a diet and fails to teach healthy habits, since people can eat whatever they want on non-fast days (Whiteman, 2015). The benefits of fasting certainly cannot replace a healthy lifestyle. Nutritious, moderated eating habits, and regular exercise produce many of the same health benefits and similar rates of weight loss. In an article published in Maturitas, the authors note that unlike dieting, intermittent fasting may be sustainable. However, if healthy-weight individuals desire to fast for health reasons then the cycle would have to be adjusted for them in order to prevent weight loss (Skaznik-Wikiel, Malgorzata, 2014).
Long or frequent types of fasting are typically more risky than short or infrequent fasting. The level of risk for all types of fasting varies depending on the individual’s age, physical activity level, and medical conditions. Pregnancy and vulnerability to eating disorders are other high-risk conditions. If the underlying motive is health, not weight loss, then short-term or infrequent fasting may be part of a healthy lifestyle for some individuals. It’s important to remember that eating nutritious foods, exercising, and meditating can produce similar health benefits and weight loss rates as fasting. These habits should be implemented along with fasting and can be used safely instead of fasting for anyone who might be at risk. It’s also probably wise to consult your doctor if you conclude that short, infrequent fasting is something you’d like to try.
A Johnstone. (2015). Fasting for weight loss: an effective strategy or latest dieting trend? International Journal of Obesity (2015) 39, 727–733 Retrieved from http://www.nature.com.ezproxy1.lib.asu.edu/ijo/journal/v39/n5/full/ijo2014214a.html
Katie. (2016). Fasting for Mental Health – Does it Work? TheMindScienceGap.org. Retrieved from http://www.mindthesciencegap.org/2013/04/10/fasting-for-mental-health-does-it-work/
Leslie, Mitch. (2015). Short-Term Fasting May Improve Health. Sciencemag.org. Retrieved from http://www.sciencemag.org/news/2015/06/short-term-fasting-may-improve-health
Monson, Nancy. (2014). Life in the Fasting Lane: Does Intermittent Fasting Work And is it Healthy? Women’s Health Magazine. Retrieved from http://www.womenshealthmag.com/weight-loss/intermittent-fasting
Paleo Leap, LLC. (2016). Paleoleap.com. Retrieved from http://paleoleap.com/long-fasts/
Skaznik-Wikiel, Malgorzata E ME. (2014). The health pros and cons of continuous versus intermittent calorie restriction: more questions than answers. Maturitas Vol. 79. No. 3. pp. 275-278. Retrieved from http://pl8cg5fc8w.search.serialssolutions.com.ezproxy1.lib.asu.edu/?sid=Entrez:PubMed&id=pmid:25216760
Seliger, Susan. (2016). Is Fasting Healthy? WebMD.com. Retrieved from www.webmd.com/deit/features/is_fasting_healthy#1
Warren, Rachel. (2011). The Facts on Fasting for Your Health. Everydayhealth.com. Retrieved from http://www.everydayhealth.com/diet-nutrition/the-facts-on-fasting-for-your-health.aspx
Whiteman, Honor. (2015). Fasting – Health Benefits and Risks. Medical News Today. Retrieved from http://www.medicalnewstoday.com/articles/295914.php
About Rebecca: Rebecca Rullo is a Nutrition Communication student at Arizona State University. She loves being outside, learning, having deep conversations, and getting to the source of an issue.