What Is 18:6 Intermittent Fasting + How to Start?

Written and medically reviewed by Nicole Grant, RD

Let’s face it: No one has time for complicated health solutions. While getting (and staying) healthy is never quick nor easy, your wellness journey should be sustainable for your lifestyle. The amazing thing about intermittent fasting, a form of time-restricted feeding, is that it can work for most people and bring about transformational health benefits, like weight loss, longevity, and more.

Unlike traditional dieting, which revolves around strict calorie counting or eliminating certain food groups, IF focuses on when you eat, rather than what you eat. The 18:6 intermittent-fasting protocol can be a great option for those seeking simplicity and flexibility.

Read on for a closer look at 18:6 intermittent fasting, its benefits, and how you can get started on the path towards a healthier, more energized you.

What Is 18:6 Intermittent Fasting?

18:6 intermittent fasting is a time-restricted feeding protocol that combines an 18-hour fasting period with a 6-hour eating window. You have the freedom to adjust the fasting and feeding windows to align with your daily routine; for example, if your first meal of the day is at noon, you’d eat the rest of your daily calories before 6 p.m. and consume only fasting-approved beverages for the remainder of the day.

The 18:6 fast is a little longer than its popular counterpart, the 16:8 fast, but this extended fasting window may yield greater results for metabolic health as it allows more time for your body to tap into its fat stores for energy.

How Does 18:6 Intermittent Fasting Affect Your Body and Hormones?

When you adhere to the 18:6 intermittent-fasting protocol, you can expect many notable physiological changes to occur.Here’s a look at how 18:6 fasting affects your body and the key hormonal responses associated with it:

  • Insulin: Insulin is a hormone released by the pancreas, and it plays a crucial role in regulating blood-sugar levels. During an 18-hour fast, insulin levels decrease significantly, allowing your body to better utilize stored glycogen and fat for energy. 
  • Ghrelin: Ghrelin, also referred to as the “hunger hormone,” is produced in the stomach and signals hunger to the brain. When you first begin an IF protocol, ghrelin levels initially increase. As you adapt to the 18:6 routine and follow it consistently, ghrelin levels tend to stabilize, and hunger pangs become less pronounced over time. This adaptation makes the fasting period more manageable as a long-term solution.
  • Leptin: Leptin, the “satiety hormone,” is responsible for signaling fullness and regulating energy balance. When practiced consistently, intermittent-fasting plans, such as the 18:6 IF protocol, can improve leptin sensitivity. This allows you to better recognize feelings of satiety and may reduce overeating.
  • Cortisol: Cortisol is the stress hormone, released by the adrenal glands during a stress response. Typically, fasting increases cortisol levels, so the longer your fasting window, the higher your cortisol levels will be compared to baseline. Once you eat, however, cortisol levels return back to normal. Long term, consistently doing a 18:6 fast may help cortisol function over time. Although research is limited, one study showed that early time-restricted feeding (TRF) can lead to lower evening cortisol levels. This may help reduce overall stress levels in your body and even result in living longer and sleeping better.

These hormonal adaptations can contribute to better weight management, improved metabolic health, increased longevity, and overall well-being. Now, let’s explore the numerous benefits that 18:6 fasting has to offer, which go far beyond the confines of traditional diet and weight-loss strategies.

Aids in Weight Loss

Weight loss is one of the key benefits of 18:6 intermittent fasting. By restricting your eating window to 6 hours, you naturally consume fewer calories, potentially leading to a calorie deficit and healthy, sustainable weight loss. 

Additionally, the fasting duration of 18 hours allows more time for your body to burn through its glycogen stores and draw from its own fat stores for energy. This facilitates fat burning and further supports your weight-loss journey. It’s worth noting, however, that the amount of weight you can lose with 18:6 intermittent fasting depends on various factors, including your overall health and lifestyle.

Reduces Inflammation and Lowers Risk of Chronic Disease

Inflammation is a key driver in many chronic-health issues, including arthritis, heart disease, diabetes, and even some types of cancer. Intermittent fasting has been shown to inhibit the development of plaque within the arteries by reducing the concentration of inflammatory markers, such as IL-6, homocysteine, and CRP. By lowering these inflammatory markers, IF can help lower the risk of developing chronic disease and promote overall health and longevity.

Boosts Cognitive Function

While fasting, your body can experience a wide range of short-term positive effects that include a boost in mental clarity and cognitive function. Research is ongoing, but intermittent fasting shows promise as a preventative tool against issues like dementia and age-related cognitive decline. 

18:6 intermittent fasting may also promote the production of new brain cells and enhance the performance of existing neurons by stimulating brain-derived neurotrophic factor (BDNF). Increased BDNF levels are associated with improved memory, learning, and overall cognitive performance.

Burns Fat

Extending your overnight fast to at least 12 hours has been shown to activate your body’s natural fat-burning processes. Therefore, 18:6 intermittent fasting gives your body several hours to benefit from burning fat as a priority fuel source, even at rest. Research suggests that fat burning is amplified further when you engage in fasted movement, so if you really want to maximize your fat burning, try to get active before you break your fast.

Promotes Autophagy

Autophagy is the body’s natural cellular clean-up process. It clears away damaged cellular parts, removes damaged proteins, and promotes cellular repair and regeneration. 

Autophagy is a gradual process that increases over time with peak efficiency at around 36–72 hours of fasting; however, studies show that autophagy can kick in as early as 17 hours of fasting, which makes the 18:6 intermittent-fasting model ideal for promoting detoxification and cellular repair. Promoting autophagy may slow down the aging process and reduce the risk of age-related diseases. 

Improves Gut Health

Gut health is strongly connected to mental and physical well-being. IF has been found to positively impact gut health by giving the digestive system a break. It promotes a diverse gut microbiota and enhances the balance of beneficial bacteria in the digestive system. This can contribute to improved digestion, nutrient absorption, and overall gut health.

Improves Metabolic Health

The 18:6 intermittent-fasting protocol has been associated with several metabolic benefits. Research suggests that IF can improve insulin sensitivity and enhance the body’s ability to respond to insulin effectively.

This improvement can help regulate blood-sugar levels, reduce the risk of insulin resistance, and potentially lower the likelihood of developing type-2 diabetes. Additionally, intermittent fasting has a positive impact on multiple cardiovascular risk factors such as cholesterol, obesity and hypertension.

How to Start 18:6 Fasting

The average American typically consumes most of their calories during a 14–15-hour eating window. Following an 18:6 fasting plan is an excellent goal to work towards, but you may need to take it slow at first. Here’s the best way to approach 18:6 if you’re new to intermittent fasting.

#1) Ease In

Start with a shorter fasting period and work your way up; a 12:12 fasting plan is a great way to start. Simply consume your meals within a 12-hour period (for instance, 8 a.m. and 8 p.m.) with an optional snack in between.

#2) Gradually Increase Your Fasting Period

Once you’ve mastered the 12:12, gradually increase your fasting period, working up to 14:10, then 16:8, and eventually 18:6 intermittent fasting over the next several weeks.

#3) Listen to Your Body

While you can do 18:6 intermittent fasting every day, it’s okay to occasionally modify your fasting schedule. If you’re extra hungry, had a harder workout, or just weren’t able to get enough nutrients the day before, shorten your fasting period. But if you’re feeling really good and able to sustain a longer fast, go for it!

#4) Use a Fast-Tracking App

While you can look at the clock to determine when it’s time to start and stop fasting, few people are able to build a fasting habit this way. If you’re committed to starting or maintaining a fasting practice and want to hold yourself accountable, a fast-tracking app like Zero can be a fantastic tool. With Zero, you have access to exclusive Challenges, premium content, and personalized insights into what happens inside your body during a fast, focused on promoting your natural ability to burn fat. Zero members have lost millions of pounds, and you can, too! 

What to Eat on an 18:6 Fast

While it’s true that intermittent fasting primarily focuses on when, rather than what, you eat, you’ll get the best results if you prioritize a healthy, balanced diet during your eating window. Here are some key principles to keep in mind:

  • Embrace Whole Foods: Prioritizing whole, unprocessed foods is the best way to maximize the benefits of intermittent fasting. Focus on including a variety of fruits, vegetables, proteins, legumes, nuts, seeds, and healthy fats in your meals. These foods are rich in essential nutrients, fiber, and antioxidants.
  • Prioritize Protein: Protein promotes satiety, helping you feel full and satisfied during the fasting period. It also supports muscle growth, maintenance, and repair. Aim to include minimally-processed protein sources in your meals, like poultry, fish, legumes, and Greek yogurt.
  • Incorporate Healthy Fats: Healthy fats provide energy, support brain function, and aid in the absorption of fat-soluble vitamins. Some great examples include avocados, nuts, seeds, olive, oil, and fatty fish.
  • Hydrate: Proper hydration is vital when fasting. Make sure to drink plenty of water throughout the day and include herbal teas, bone broth, and other low-calorie, sugar-free beverages to keep yourself hydrated. If fasting for metabolic health and weight-loss benefits, black coffee, unsweetened sparkling water, and plain tea are all okay to consume in both the eating and fasting windows.

Can You Do 18:6 Intermittent Fasting Five Days a Week?

Yes, you absolutely can do 18:6 intermittent fasting five days a week. This can be a great starting point or a more sustainable approach for many individuals. 

The flexibility of this fasting pattern allows you to choose the days that work best for your schedule, commitments, and personal preferences. For example, many people find it easier to adhere to an IF protocol during the work week, when they have a more structured routine and schedule. 

How Long Does It Take for 18:6 Intermittent Fasting to Work?

We all have different bodies, lifestyles, and fasting goals, so there’s no one-size-fits-all answer to how long it takes to feel the impact of an 18:6 fasting protocol. Many people begin to experience improved mental clarity, increased energy, and stabilized blood-sugar levels after just a few days of fasting.

Weight loss is one of the primary goals for many people considering intermittent fasting. While it’s important to remember that weight loss is a gradual process, adopting an 18:6 intermittent-fasting routine can help you lose weight faster. One study showed that twenty-eight days of 18-hour fasts produced about a 3% change in weight loss. 

The short-term benefits of following an 18:6 fasting plan are often attained a little faster than other types of IF with shorter fasting periods. While short-term effects and visible changes can be motivating, it’s important to remember the substantial, long-term benefits of 18:6 fasting, which include improved metabolic health, lower risk of chronic disease, enhanced cognitive function, and potential longevity benefits associated with cellular-repair processes like autophagy. Consistency is the key to experiencing these long-term advantages. 

What Are the Challenges of 18:6 Fasting?

While 18:6 fasting offers numerous benefits, it’s important to acknowledge that it comes with its own set of challenges. 

In the early stages of adopting 18:6, you may experience hunger pangs and cravings. However, as you consistently adhere to the routine and consume enough nutrients within your eating window, these feelings should decrease over time as your body adapts.

Fasting for 18 hours can also sometimes pose challenges in social situations. You may need to plan ahead to align your eating window with social engagements or events. Additionally, if you have specific dietary needs or preferences, it can be more challenging to ensure adequate nutrient intake with an already restricted eating window. Planning ahead is key here.

Remember that everyone’s experience with fasting is unique, and what may be easy for one person can be hard for someone else, and vice versa. Listen to your body, make adjustments as needed, and turn to your community (and Zero!) for support.

Who Shouldn’t Follow an Intermittent-Fasting 18:6 Plan?

While intermittent fasting is generally considered safe for most individuals, those with certain health conditions should consult with their doctor before considering any type of fasting regimen. These conditions include:

  • Those who are underweight or struggle to gain weight
  • Those with a history of an eating disorder
  • People who take heart-health or blood-pressure medication
  • Patients with diabetes or other blood-sugar issues

Conclusion: 18:6 Is a Solid Option for Health and Weight-Loss

By adopting an 18:6 intermittent-fasting schedule, you have the opportunity to optimize your longevity, improve your metabolic health, and achieve your weight-management goals. When adopting an 18:6 fasting schedule, remember to start slow, listen to your body, and make adjustments as needed.

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Nicole Grant, RD
Posted in Health & Science

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