Intermittent fasting: trend, fact, or hoax?
Intermittent fasting has been one of the hottest diet trends over the past decade, but is it more hoax than truth? Here’s what you need to know about IF and how you can nutritionally support your clients if they choose to participate in this eating style.
Intermittent fasting (IF) has taken the health and wellness world by storm. Since its emergence in 2012, this eating style has been the focus of many scientific studies and a highly debated topic within the medical community . Yet with so many people jumping on board and singing its praises, does IF really live up to the hype?
While the verdict is still out on this one, studies show that there are some potential health benefits, including weight loss, improved heart health, blood sugar control, neuroprotection and protection against some forms of cancer. However, it can also lead to inadequate nutrition intake and subsequent nutrient deficiencies, reproductive problems, reduced sports performance, and even disordered eating.
As a nutrition professional, it’s important to look at all aspects of your client’s health so you can provide the best nutritional guidance possible. This is especially true when it comes to “trendy” diets, as you need to sort through the noise to determine the best approach for your client’s health and wellness needs. But what do you need to know about IF, and how can you support your clients if they want to follow this eating style? Let’s start by understanding what it is, and the health outcomes surrounding it.
What is intermittent fasting?
Intermittent fasting focuses on periods of consumption and fasting, as it’s theorized that this is a way to allow our bodies to reset and function at an optimum level .
IF’s main characteristic is alternating between fasting and eating for certain times during the day or week. This differs from other popular diets, because while they have strict dietary requirements, time is the only real restriction with IF. Essentially, you can eat whatever you want, as long as it’s within your “eating window”.
There are three primary schedules: alternate day fasting, modified fasting, and time restricted fasting .
- Alternate day fasting. This method is just as it sounds. On one day, foods are consumed as normal, with an emphasis on a healthy diet, and the following day is a fast with only zero calorie beverages, such as water and black coffee, allowed.
- Modified fasting. This approach focuses on a significant caloric reduction rather than a complete fast. It follows a 5/2 plan, where on five days of the week, a normal diet is consumed. On the remaining 2 days, women are allowed 500 calories, and men can have 600 calories.
- Time restricted eating. This is the most popular plan where there is not a fasting day, but rather fasting periods. For instance, the 16/8 method implements a 16 hour fasting period followed by an 8 hour window to consume 3 meals.
Though IF does not dictate any specific dietary recommendations, limiting your client’s intake to a specific eating window often reduces their caloric intake which can result in weight loss for some.
Benefits of IF
Intermittent fasting has been shown to protect against chronic diseases, help with glucose management, and even improve longevity. Let’s dive a bit deeper into the research to understand more about the health benefits of IF.
May protect against chronic diseases.
Human studies show that IF may provide protection against chronic diseases like metabolic syndrome and cardiovascular disease [2,6].
Decreased risk of cancer.
Research indicates that IF may prove beneficial in both the treatment and prevention of certain cancers, and may be as effective as chemotherapy . However, more studies are needed in this area.
Studies have found that people (particularly obese adults) who participated in time-restricted feeding lost more weight than those who didn’t fast, regardless of intentional caloric restriction [4,7].
Time-restricted fasting may help control blood sugar levels and increase insulin sensitivity, both of which are important to monitor for managing and preventing type 2 diabetes [8,9].
Easier to stick to.
Since time is the only restriction with IF, many people find this approach easier to stick to in the long run compared to other diets.
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Are there any drawbacks to intermittent fasting?
Although intermittent fasting can provide health benefits for many people, this method may not be for everyone. Here are some potential drawbacks to IF.
Lowered energy levels.
Research shows that IF can affect energy levels, which can cause a decrease in physical activity during these periods .
Fasting for long periods of time can cause headaches, lightheadedness, mood changes, constipation, fatigue, and irritability if not approached correctly. However, these symptoms can ease over time as the body adapts.
Not recommended for certain populations.
This eating method isn’t recommended for pregnant and lactating women, young children, the elderly, those with compromised immune systems, or people who have had (or are struggling with) an eating disorder.
If not monitored carefully, IF can lead to inadequate nutrition intake and subsequent nutrient deficiencies, reproductive problems, and reduced sports performance, and might even mask disordered eating [10,11]. Your clients may also find IF hard to manage in certain social situations.
How to nutritionally support clients
If you have a client who wants to try IF, here are some ways you can nutritionally support them to ensure they meet their health and wellness goals.
- There’s more than one way to do it. The beauty about IF is that your client can choose which method works best for them. For instance, if they don’t feel hungry in the morning, the 16/8 method may be easier; whereas if they prefer to eat out, the 5/2 method may be a better fit since they can choose which days they want to fast.
- Create a balanced diet. While IF doesn’t have any dietary restrictions, it’s still important for your clients to get enough nutrients throughout the day. You can help them achieve this with a carefully curated meal plan.
- Track water intake. Drinking enough water is vital for everyone, but especially if your client is fasting. This will not only keep them hydrated, but it can also help them feel more full throughout the day.
- Monitor for warning signs. If your client has a history of disordered eating, or you think they may be at risk for developing one, IF might not be the right fit for them. However, even if your client doesn’t fall into either of these categories, you should still be on the lookout for any signs of an eating disorder, in case one may arise.
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Intermittent fasting is a dietary approach that involves eating and fasting for specific periods of time throughout the day or week and leads to changes in both your hormone levels and metabolism. While studies have shown positive results from time-restricted eating, it can also lead to inadequate nutrition intake and subsequent nutrient deficiencies, reproductive problems, reduced sports performance, and even disordered eating. As a nutrition professional, you can help your clients determine if IF is right for them, and if so, it’s important to make sure they are meeting their nutrient needs, drinking enough water, and feeling good during their fasting periods.
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- Orenstein, B. (2014). Intermittent Fasting: The Key to Long-Term Weight Loss?. Today's Dietitian. Retrieved from https://www.todaysdietitian.com/newarchives/120914p40.shtml.
- Mattson, M., Longo, V., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing Research Reviews, 39, 46-58. https://doi.org/10.1016/j.arr.2016.10.005
- Gordon, B. (2019). What is Intermittent Fasting. Academy of Nutrition and Dietetics. Retrieved from https://www.eatright.org/health/wellness/fad-diets/what-is-intermittent-fasting.
- Teong, X., Hutchison, A., Liu, B., Wittert, G., Lange, K., Banks, S., & Heilbronn, L. (2021). Eight weeks of intermittent fasting versus calorie restriction does not alter eating behaviors, mood, sleep quality, quality of life and cognitive performance in women with overweight. Nutrition Research, 92, 32-39. https://doi.org/10.1016/j.nutres.2021.06.006
- Lennon, A. Is intermittent fasting or calorie restriction better for weight loss? Medical News Today. (2021). Retrieved from https://www.medicalnewstoday.com/articles/intermittent-fasting-no-better-than-calorie-restriction-for-weight-loss.
- The Endocrine Society. (2021, September 22). Intermittent fasting can help manage metabolic disease: Popular diet trend could reduce the risk of diabetes and heart disease. ScienceDaily. Retrieved June 13, 2022 from www.sciencedaily.com/releases/2021/09/210922090909.htm
- Gabel, K., Hoddy, K. K., Haggerty, N., Song, J., Kroeger, C. M., Trepanowski, J. F., Panda, S., & Varady, K. A. (2018). Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutrition and Healthy Aging, 4(4), 345–353. https://doi.org/10.3233/nha-170036
- Armutcu, F. (2019). Fasting may be an alternative treatment method recommended by physicians. Electronic Journal of General Medicine, 16(3). https://doi.org/10.29333/ejgm/104620
- Crupi, A. N., Haase, J., Brandhorst, S., & Longo, V. D. (2020). Periodic and intermittent fasting in diabetes and cardiovascular disease. Current Diabetes Reports, 20(12). https://doi.org/10.1007/s11892-020-01362-4
- Tong, Q., & Xu, Y. (2012). Central Leptin Regulation of Obesity and Fertility. Current obesity reports, 1(4), 236–244. https://doi.org/10.1007/s13679-012-0025-8
- Levy, E., & Chu, T. (2019). Intermittent fasting and its effects on athletic performance. Current Sports Medicine Reports, 18(7), 266–269. https://doi.org/10.1249/jsr.0000000000000614