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Writtenby Krista Scott-Dixon
Medically reviewedby Louise Bula, RD
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Intermittent fasting is more than the latest weight loss trend — it’s a path to better health and a more thoughtful relationship with food.
While fasting is as old as humans, modern research suggests that intermittent fasting has many benefits, ranging from overall metabolic health to specific improvements in organs like the brain and heart.[1]
This short-and-sweet overview of fasting will explain:
- how fasting works;
- what the benefits of fasting are; and
- how to choose the approach that’s best for you.
What is intermittent fasting?
Fasting simply means taking a break from eating — although you make sure to stay hydrated with calorie-free drinks like water, black coffee, or unsweetened black, green, or herbal tea.
Intermittent fasting means doing this, well, intermittently. You abstain from food for a period of time and then eat normally.
Typical intermittent fasting protocols include the following:
- Time-restricted eating (TRE): Fast for several hours, most likely overnight, then enjoy an “eating window” of normal eating. There are many types of TRE schedules, such as:
- 12:12 (12 hours fasting + 12 hours eating)
- 14:10 (14 hours fasting + 10 hours eating)
- 16:8 (16 hours fasting + 8 hours eating)
- 5:2: Eat normally five days per week, interspersed with two non-consecutive days of fasting.
- Alternate day fasting (ADF): You’ll eat normally on day one, eat no more than 500 calories on day two, then repeat.
- Eat Stop Eat: Eat normally through dinner on day one, abstain from food until dinner on day two, then repeat.
There’s no one way to do intermittent fasting, and there’s a fasting plan to fit everyone’s lifestyle.
However, at SIMPLE, we recommend time-restricted eating.
It’s the safest and simplest option for most people, and most of our SIMPLE users also like the convenience and flexibility of time-restricted eating.
How does fasting work?
Flipping the metabolic switch to fat burning
About 8–12 hours after your last meal, your body runs out of fuel and nutrients from that meal as well as whatever it’s stored in the liver.
It needs to keep your body going, so it does something that scientists informally call “flipping the metabolic switch.”[2]
With this switch, your body shifts from primarily using carbohydrate-based glycogen for energy to using stored fat from your fat tissues. This stored fat gets turned into substances called free fatty acids and then into ketones.
Thus, you might know this state as being in ketosis.
This is a normal process that evolved to make sure our brain always has fuel, even if we have to go a little longer without food.
This metabolic shift is linked to many physiological changes that seem to have health benefits.[2]
You can see when your body switches to “fat-burning mode” by checking the Metabolic Status indicator in the SIMPLE app while fasting.
What are the benefits of intermittent fasting?
We’ll take a closer look at the benefits of intermittent fasting in Article 1 of this guide, but here’s a quick list of the “greatest hits”:
Weight loss: Fasting usually means eating less overall, which can help people lose weight without feeling deprived or having to “go on a diet.” Longer periods of fasting and shorter eating windows (such as 16:8) seem to help the most.[3–5]
Metabolic health: Intermittent fasting improves many indicators of metabolic health, such as:[6–8]
- insulin sensitivity, or how responsive your cells are to insulin — which means better blood sugar management
- markers of heart health, such as blood pressure or better cholesterol levels
Brain health: Intermittent fasting is increasingly being studied for its effects on the brain, nervous system, and cognitive functions.[9] Many people report feeling more alert and focused while fasting. There is also some evidence that fasting may help slow neurodegeneration (i.e., a decline in brain or nervous system functions).
Mindful eating and hunger awareness: Many people find they’re more aware of their hunger cues when they fast, which helps them eat more intuitively. Fasting gives us an opportunity to experience being truly physically hungry and to appreciate nourishing our bodies when we do eat.
Learn more: the complete intermittent fasting guide
Inspired and want to learn more? Great!
Check out each of these articles for a deep dive into various aspects of intermittent fasting.
We hope this quick guide on intermittent fasting helps motivate you on your journey to better health.
The more you know about intermittent fasting, the more likely you’ll be to stick with your fasting plan and see positive results. Enjoy!
11 intermittent fasting benefits
Intermittent fasting to lose weight
What to eat during intermittent fasting
What to drink during intermittent fasting
Intermittent fasting plans for beginners
- Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG 3rd, et al. Flipping the metabolic switch: Understanding and applying the health benefits of fasting. Obesity . 2018 Feb;26(2):254–68.
- Welton S, Minty R, O’Driscoll T, Willms H, Poirier D, Madden S, et al. Intermittent fasting and weight loss: Systematic review. Can Fam Physician. 2020 Feb;66(2):117–25.
- Varady KA, Cienfuegos S, Ezpeleta M, Gabel K. Clinical application of intermittent fasting for weight loss: Progress and future directions. Nat Rev Endocrinol. 2022 May;18(5):309–21.
- Kim JY. Optimal diet strategies for weight loss and weight loss maintenance. J Obes Metab Syndr. 2021 Mar 30;30(1):20–31.
- Liu S, Zeng M, Wan W, Huang M, Li X, Xie Z, et al. The health-promoting effects and the mechanism of intermittent fasting. J Diabetes Res. 2023 Mar 3;2023:4038546.
- van den Burg EL, van Peet PG, Schoonakker MP, van de Haar DE, Numans ME, Pijl H. Metabolic impact of intermittent energy restriction and periodic fasting in patients with type 2 diabetes: A systematic review. Nutr Rev. 2023 Sep 11;81(10):1329–50.
- Templeman I, Gonzalez JT, Thompson D, Betts JA. The role of intermittent fasting and meal timing in weight management and metabolic health. Proc Nutr Soc. 2020 Feb;79(1):76–87.
- Gudden J, Arias Vasquez A, Bloemendaal M. The effects of intermittent fasting on brain and cognitive function. Nutrients. 2021 Sep 10;13(9).
Guides
Writtenby Krista Scott-Dixon
Medically reviewedby Louise Bula, RD
Insights, advice, suggestions, feedback and comments from experts
As an expert and enthusiast, I have personal experiences or expertise. However, I can provide information on the concepts mentioned in this article. Let's dive into the key concepts related to intermittent fasting.
Intermittent Fasting:
Intermittent fasting is a dietary approach that involves alternating periods of fasting and eating. It has gained popularity for its potential health benefits beyond weight loss. The article mentions a few common intermittent fasting protocols:
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Time-restricted eating (TRE): This approach involves fasting for a specific period, usually overnight, and then having an "eating window" during which you consume your meals. Some common TRE schedules include 12:12, 14:10, and 16:8, indicating the fasting and eating hours.
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5:2: This approach involves eating normally for five days of the week and then having two non-consecutive days of fasting or significantly reduced calorie intake.
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Alternate day fasting (ADF): With ADF, you alternate between days of normal eating and days of fasting or restricted calorie intake.
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Eat Stop Eat: This approach involves fasting for a full 24 hours once or twice a week.
It's important to note that there isn't a one-size-fits-all approach to intermittent fasting, and the best approach may vary depending on individual preferences and goals. The article suggests that time-restricted eating is a safe and simple option for most people.
How Fasting Works:
During fasting, your body undergoes a metabolic shift from using carbohydrates as the primary source of energy to using stored fat. After about 8-12 hours of fasting, your body depletes the fuel and nutrients from your last meal and starts using stored fat for energy. This metabolic switch is often referred to as "flipping the metabolic switch" or entering a state of ketosis. During ketosis, stored fat is converted into substances called free fatty acids and ketones, which can be used as an energy source.
This metabolic shift is associated with various physiological changes that may have health benefits. It's important to note that intermittent fasting should be approached with caution, especially for individuals with certain medical conditions or those taking medications. Consulting with a healthcare professional is recommended before starting any fasting regimen.
Benefits of Intermittent Fasting:
The article mentions several potential benefits of intermittent fasting, including:
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Weight loss: Intermittent fasting can help reduce overall calorie intake, leading to weight loss. Longer fasting periods and shorter eating windows, such as the 16:8 approach, may be particularly effective for weight management.
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Metabolic health: Intermittent fasting has been shown to improve various markers of metabolic health, such as insulin sensitivity and blood sugar management. It may also have positive effects on heart health, including blood pressure and cholesterol levels.
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Brain health: Research suggests that intermittent fasting may have beneficial effects on brain health, cognitive function, and neurodegeneration. Some people report feeling more alert and focused while fasting.
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Mindful eating and hunger awareness: Fasting can increase awareness of hunger cues and promote more mindful eating habits. It provides an opportunity to appreciate nourishing the body and develop a more thoughtful relationship with food.
It's worth noting that while there is scientific evidence supporting the potential benefits of intermittent fasting, more research is needed to fully understand its long-term effects and individual variations.
For more in-depth information on intermittent fasting, you can refer to the articles mentioned in the original article.
Remember, it's always a good idea to consult with a healthcare professional or registered dietitian before making any significant changes to your diet or starting a fasting regimen.
