Intermittent fasting (IF) has become a widely discussed dietary strategy, lauded for its potential benefits ranging from weight management to improved mental clarity. Among the various IF schedules, the 18:6 method stands out as a popular and potentially sustainable approach. This article delves into the details of 18:6 intermittent fasting, exploring its mechanisms, benefits, and practical considerations for implementation.
Understanding Intermittent Fasting
Intermittent fasting isn't a diet in the traditional sense, but rather an eating pattern. It revolves around cycling between periods of eating and voluntary fasting on a regular schedule. There are different types of intermittent fasting schedules. Time-restricted feeding, alternate day fasting, and full day fasting are all different names for intermittent fasting that depend on when eating occurs. Unlike diets that dictate what you should eat, IF focuses on when you should eat. This flexibility makes it an attractive option for individuals seeking to manage their weight and improve their health without strict dietary restrictions.
Decoding the 18:6 Intermittent Fasting Method
An 18:6 intermittent fasting pattern is a type of time-restricted eating that involves eating within a 6 hour window of time each day followed by an 18-hour fasting period. The 18:6 method involves a daily 18-hour fasting period followed by a 6-hour eating window. During the 18-hour fast, consumption is typically limited to water, black coffee, and herbal tea, as these contain minimal calories and are unlikely to disrupt the fasting state. There is no defined time of day for the eating window or fasting period. A popular 18:6 fasting pattern is to eat between 12pm and 6pm. This often means skipping breakfast and just eating lunch and dinner. This pattern often fits people’s lifestyles more easily than patterns with longer fasting periods, such as 20:4 or OMAD (one meal a day) which require a more dramatic shift in one’s eating routine. Some may also choose to do an 18:6 intermittent fast only several days each week while stretching their eating window on certain days, like weekends or holidays, to create more flexibility in their lifestyle. This approach allows for flexibility, as individuals can choose the 6-hour eating window that best suits their daily schedule and lifestyle.
How 18:6 Intermittent Fasting Works: Fueling the Body
During a fast, the body relies on stored nutrients for energy. Glycogen (stored glucose from carbohydrates) powers the body for the first four to six hours of a fast. When glycogen stores become low, the liver begins producing glucose from non-carbohydrate sources. Glucose is the body’s preferred energy source and powers all organs including the brain and muscle. After a few hours of fasting, the body taps into stored fat for fuel. The body can convert fat into glucose to maintain baseline blood sugar levels. Using stored fat for energy contributes to fat loss and shifts in body composition. The body relies more on fat for energy as fasting time increases. Ketosis is another adaptation that occurs with prolonged fasting. Ketosis occurs when the body converts fat into ketones, a molecule the body and brain use for energy when glucose is not readily available. Ketosis can occur after just 12 hours of fasting or with a diet very low in carbohydrates. It is possible to enter ketosis with an 18:6 intermittent fasting schedule. However, whether you enter ketosis depends on multiple factors, such as your individual metabolism, food choices, and for how long you have been doing intermittent fasting. Fat adaptation, a process in which the body can efficiently burn fat as a fuel source, can occur as the body gains metabolic flexibility. Metabolic flexibility refers to the body’s ability to switch between using glucose and fat for energy. Some research indicates greater metabolic flexibility may reduce the risk of chronic diseases.
Potential Benefits of the 18:6 Fasting Schedule
An 18:6 intermittent fasting diet has multiple benefits and may include the following:
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- Weight Loss and Changes in Body Composition: During the 18 hour fasting period, the body may increasingly rely on burning stored body fat for energy. The restricted eating window can help to reduce overall calorie intake, as long as you don’t compensate with eating more during that time. Cycling your calories over a 24-hour time period can help prevent the slowdown in your metabolism that often occurs with calorie restriction. Additionally, the after 6 diet works for many people because they find it easier to stick to than a low-calorie diet.
- Increased Metabolic Flexibility: Intermittent fasting can promote insulin sensitivity and improve cardiovascular health as a result of reduced inflammation and weight loss. Insulin sensitivity refers to how well the body responds to insulin. Insulin is the key that allows glucose to be removed from the bloodstream for use by muscles and organs. Insulin resistance (when the body is less responsive to insulin) contributes to the development of type 2 diabetes.
- Improved Blood Sugar Management: Intermittent fasting has been shown to help decrease blood sugar levels in those with excessive levels as well as promote intentional weight loss. More research is needed, however, to determine if intermittent fasting fosters blood sugar management apart from its effects on supporting weight loss, since weight loss is known to lower blood sugar levels.
- Improved Heart Health: Following an 18 hour fasting diet can improve your insulin resistance, reduce inflammation, improve metabolic syndrome indicators, and enhance the lipid profile. Thanks to a combination of these effects, IF can help support your heart health and lower the cardiovascular risk in the long run.
- Better Bowel Movements as a Result of Changes to the Gut Microbiome:
- Mental Clarity and Focus: Mental clarity and focus also often get a boost due to the production of ketones, which can reduce inflammation and have cognitive benefits.
- Cellular Repair: Research also suggests that intermittent fasting can induce autophagy, which is a process in which the body repairs cells.
- Simplified Meal Planning: In addition to direct benefits to the body, intermittent fasting can also help simplify meal planning. With intermittent fasting, you may only need to plan for two meals. For some people, the shorter eating window may mean less snacking. Still, it is important to prioritize nutrient-dense foods like non-starchy vegetables, whole grains, and lean proteins with meals. While for some this may support a decrease in mental preoccupation with food and lead to healthier eating habits, intermittent fasting may not be appropriate for those with active eating disorders or who have a history of eating disorders, since fasting may perpetuate unhealthy eating behaviors such as excessive restriction.
Making the Most of Your Eating Window: What to Eat
Intermittent fasting is mostly about when you eat rather than what you eat. Nevertheless, in order to lose weight and receive all the benefits of IF, you need to make sure that you maintain your state of fasting and don’t break it. Also, it’s important to have more nutritious and healthy meals during your eating windows to fuel your body well and stimulate effective weight loss.
As was mentioned earlier, IF isn’t that much about controlling what you eat but rather about sticking to the chosen schedule. Nevertheless, if you are fasting 18 hours a day and then make up for all the lost calories and eat lots of unhealthy, processed foods, chances are that your weight loss progress will be not visible or very slow.
To maximize the benefits and results of your IF, you should focus on choosing nutrient-rich foods. You need to have balanced meals that include:
- Whole grains, such as rice, oats, quinoa, and barley.
- Lean proteins, such as fish, seafood, eggs, lean meat, poultry, and legumes.
- Healthy fats, such as olive oil and avocados.
- Fruits and vegetables.
Practical Tips for Implementing 18:6 Intermittent Fasting
- Start Gradually: If you're new to intermittent fasting, consider starting with a 12 hour fast. Over time, you can lengthen your fasting period and shorten your eating window. This gradual approach can help you assess what pattern feels best.
- Hydrate Well: It is important to maintain adequate hydration and sufficient nutrient intake when practicing intermittent fasting. Hydrate well during the fasting and eating windows.
- Prioritize Nutrient-Dense Foods: Consume nutrient-dense foods during the eating window to ensure adequate daily nutrition despite less time for eating. A Season Health registered dietitian (RD) can help ensure you’re getting the right amounts of food during the eating window. A RD works with you to make sure your diet is nutritionally complete. A Season Health registered dietitian can help you navigate any side effects like constipation that can occur with dietary changes.
- Listen to Your Body: Pay attention to how your body feels and adjust your eating window and fasting schedule as needed.
- Plan Your Meals: Develop your 18 6 fasting meal plan in advance. Getting started with any diet can be rather hard. However, when you plan your weekly menus and write grocery shopping lists, you should find it easier to get on the right track and sustain your new diet.
- Incorporate Physical Activity: Integrate physical activity. Whether it’s morning yoga or running-any form of physical activity will have a positive effect on your weight loss journey. Besides, being active has a positive impact on your mental health, which can help you withstand your dietary changes more easily and reduce stress.
Potential Drawbacks and Considerations
Although some people report very positive after 6 diet results, this way of eating may not be for everyone. would be a challenge. People who prefer to graze or eat every few hours throughout the day may also find it hard to stick to this diet.
Most importantly, if you need to eat at regular intervals for health reasons, as with diabetes or hypoglycemia, intermittent fasting may not work for you. It's important to check with your doctor before starting any fasting plan.
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Intermittent fasting might not be a great choice if you:
- Get get distracted and irritable by hunger
- Have had a turbulent relationship with food or your body or your weight, since this type of restriction may be triggering
- Have kids at home, since there’s some concern that normalizing this type of eating pattern for the sake of weight loss can normalize weight anxiety and may influence your child’s relationship to food and his or her weight
Research on Time-Restricted Feeding
Time-restricted feeding (TRF) regimens have grown in popularity; however, very few studies have examined their weight loss efficacy. We conducted the first human trial (Clinicaltrials.gov - NCT03867773) to compare the effects of two popular forms of TRF (4-h and 6-h) on body weight and cardiometabolic risk factors. Cienfuegos et al. compared the effect of two popular forms of time-restricted feeding (4-h and 6-h) on body weight and cardiometabolic risk factors in adults with obesity. Adults with obesity were randomized to 4-h TRF (eating only between 3 to 7 pm), 6-h TRF (eating only between 1 to 7 pm) or a control group (no meal timing restrictions). After 8 weeks, 4-h and 6-h TRF produced comparable reductions in body weight (∼3%), insulin resistance and oxidative stress, versus controls. Energy intake was reduced by ∼550 kcal/d in both TRF groups, without calorie counting. These findings suggest that 4-h and 6-h TRF induce mild reductions in body weight over 8 weeks, and show promise as interventions for weight loss.
Initially, a single-arm 16-week study of 10-h TRF demonstrated that adults who were overweight lost 3.6% of body weight and reduced energy intake by ∼20%, without calorie counting (Gill and Panda, 2015). The next study examined the weight-loss efficacy of 8-h TRF (Gabel et al., 2018). After 12 weeks, adults with obesity lost 2.6% of body weight and reduced energy intake by ∼20% from baseline. Most recently, another single-arm trial of 10-h TRF demonstrated 3.0% weight loss and an 8% reduction in caloric intake after 12 weeks in participants with metabolic syndrome (Wilkinson et al., 2020).
After 8-weeks of 8-h TRF, pronounced reductions in fasting glucose, insulin and insulin resistance were observed (Moro et al., 2016). Improvements in insulin sensitivity and beta-cell function were also demonstrated when food intake was limited to a 6-h window in men with pre-diabetes (Sutton et al., 2018). Blood pressure is regularly decreased with this diet, (Gabel et al., 2018; Wilkinson et al., 2020), even in the absence weight loss (Sutton et al., 2018).
18/6 Fasting Weight Loss Results: A Month-by-Month Overview
Now that you know about the core principles of fasting 18/6, you might also be wondering about the results that you can get from this IF approach. Here’s a quick overview of intermittent fasting results 1 month 18:6 to help you understand what to expect:
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Week 1: When you get started with IF, you will likely experience greater hunger and cravings during the first few days. This is a natural response of your body as it adapts its metabolic processes. It's also common to experience energy crashes.
Don’t expect to see very notable 18 hour fast weight loss results during the first week. You may lose some water as your body depletes its glycogen stores but the real progress is still ahead.
Weeks 2-3: After the first week, your body will adapt to fasting and calorie restriction, leading to decreased appetite and higher energy levels. During weeks 2-3, you will gradually start noticing positive improvements, such as optimized blood sugar, better exercise performance and endurance, and reduced inflammation, which can improve the symptoms of some chronic conditions, such as PCOS.
Week 4: If you stick to an 18 6 fasting schedule for 4 weeks, you can finally notice the desired results, such as noticeable weight loss and improved body composition. The biggest 18 6 intermittent fasting results not visible to the eye will include enhanced mental clarity, more energy, faster metabolism, and overall better well-being. Also, by week 4, you will likely find it easier to stick to your schedule.
Real-Life Success with Intermittent Fasting
In January 2019, Martine Etienne-Mesubi had had enough. She was 42 years old, and she weighed 225 pounds. By the end of 2018 Ava stopped nursing, so the “eating for two” excuse wasn’t cutting it anymore. Plus, Etienne-Mesubi was concerned about developing diabetes and hypertension, which run in her family.
She knew she had to take control of her weight and her health. “Being 225 pounds and carrying on the way I was with no-holds-barred eating all the time, I realized can’t keep eating like this.”
There are a lot of different options for intermittent fasting, and Etienne-Mesubi started with 18 hours of fasting and a six-hour eating window. “In the beginning it was challenging but within two weeks it became very normal,” she says.
By April 2019 she had lost 30 pounds and her eating window had shrunk to two or three hours a day. She decided to challenge herself with one meal a day (OMAD). She figured if it didn’t work for her, she could revert to her regular intermittent fasting schedule.
Over the holidays, Etienne-Mesubi continued with intermittent fasting but gave herself an expanded eating window of six or eight hours.
Etienne-Mesubi shares her journey on her blog, podcast and Instagram. “Anybody can do this. This is something you have control over,” she says.
“I feel amazing. I feel fantastic. I have newfound confidence,” she says. “I’m saying ‘yes’ to so many things. I’m excited about life and my future with my family. I’m a better mom and a better wife.”