Intermittent Fasting for 15 Hours: What Are the Benefits of a 15-Hour Fast?

Although health-focused methods like the keto diet or calorie restriction are effective, they are often time-consuming and overly aggressive. Intermittent fasting, however, provides a more flexible and sustainable approach, effectively guiding you toward a healthier lifestyle. The 15-hour fast might just be what you are looking for.

In this article, we will cover everything you need to know about the 15:9 fast, from its benefits to practical tips for seamlessly integrating it into your daily routine.  

What Is a 15-Hour Fast?

A 15-hour fast consists of alternating between a 15-hour fasting period and a 9-hour eating window. During fasting hours you are only to drink zero-calorie beverages, while the eating window allows you to eat as much as you want and whatever foods you prefer. 

Similar to the 16:8 fast, the 15:9 fast has a manageable fasting period that allows flexibility as to when to schedule it, most of it is during sleeping hours. In addition, the long eating window can fit your usual amount of meals and snacks, which we’ll explore in more detail later. Find the perfect fasting schedule for you with Fastic’s personalized quiz. 

Benefits of a 15-Hour Fast?

The benefits of a 15-hour fast are numerous. No matter your goal, fasting can positively impact your health in the following ways: 

Weight loss

Intermittent fasting can naturally lead to weight loss and management by reducing calorie intake and inducing ketosis. 

Promote good gut health

Fasting can alter the composition of the human gut microbiome by increasing taxonomic diversity and promoting microbial remodeling.

Improve health markers

Studies have shown fasting can help improve HDL cholesterol and insulin sensitivity, and regulate blood sugar levels.

Enhance cognitive function

The metabolic, cellular, and circadian mechanisms of fasting influence the brain. This means that fasting can improve cognitive functioning and the prevention or progression of brain-related disorders. 

Cellular repair and longevity

Fasting can lead to the induction of autophagy and increase the longevity of eukaryotic cells. Autophagy can help reduce inflammation and offer anti-aging effects. 

What You Must Know Before Starting a 15-Hour Fast

Before starting any fast, it is vital to ensure you know how to go about it safely and what to expect from it. Let’s review the basics of starting a fast and how to make the best out of your fasting experience. 

• Set realistic goals

Establish concrete objectives. If weight loss is your main goal, set a clear goal weight, but make sure it is realistic and attainable. The Fastic app guides you towards your specific goal by monitoring your progress, giving you helpful tips, and an estimate of when you will achieve it.

• Prepare to commit and discover your capabilities

Starting and maintaining a fast requires self-discipline and loads of commitment. Besides gaining physical advantages, fasting can also be seen as a journey of self-discovery. Be ready to challenge yourself mentally and physically, but be safe about it — which brings us to the next topic.

• Understand the risks and benefits

Just as there are benefits, there are potential risks. Subjecting your body to fasting can be harmful if it isn’t done appropriately. Fasting can lead to side effects, such as nutrient deficiencies or digestive issues. Individuals with chronic health conditions must seek professional guidance, as the impact fasting may have on the body can be detrimental. 

Learn more about the 10 things you must know before starting intermittent fasting to help you decide if it aligns with your expectations. 

How to Do a 15-Hour Fast?

The 15-hour fast is ideal for those seeking a fast that interferes the least with their everyday routine. On average, humans tend to sleep for 7 hours, this means that half of the time you are fasting, you are sleeping! A study on time-restricted eating, a form of intermittent fasting, in adults with overweight or obesity shows that an 8 to 9-hour eating window correlates with an increase in sleep quality.

How do you incorporate a 15-hour fast into your routine? Incorporating a 15-hour fast into your day can be as simple as adjusting your eating schedule.

Determine when the best time to eat is according to your daily responsibilities. If you prefer starting your day with a full stomach, break your fast in the morning. The exact time is up to you. You could start your eating window at 8 am as you get ready for work or start it later, around 10 am. On the other hand, if you are not into eating first thing in the morning, schedule your eating window around noon, which usually tends to be lunchtime at work.

15-Hour Fasting Schedule

The following is an example of what a 15-hour fasting schedule can look like.

10:00 AM: Break fast with a nutrient-dense meal.

12:00 PM: Enjoy a snack.

2:00 PM: Have a light meal.

6:00 PM: Enjoy an abundant meal to prepare for the fasting period.

7:00 PM: Start fast.

The number of snacks and meals is completely up to you. If your day allows you to have various snacks, do so. Eating nutrient-dense snacks throughout the day provides sustained energy levels. However, if your day does not allow this, prioritize your eating window adds up to the recommended calorie intake.

Easing into the Fast

Subjecting your body to long hours of no food intake can be overwhelming, particularly if not done correctly. Don’t just start fasting for 15 hours without giving your mind and body a heads-up. Gradually introduce the fast. Start by fasting for shorter periods and slowly increase the length as your body starts to understand what is happening. The duration of this easing process can vary, from a couple of days to a few weeks. Always listen to your body and how it reacts to these changes. Your body will be the one to dictate whether the fasting plan is working or not. Don’t worry if it doesn’t, there are other fasting methods you can try until you find the one that works best with your body and goals.

What to Eat During the Eating Window

For a fast to be successful, it requires lifestyle modifications. If your diet is not as healthy as it can be, the time has come for you to change your eating habits for the better. 

Enhance your Fasting Efforts with a Nutrient-Rich Diet

Guarantee your fasting efforts bear fruit and follow a nutrient-dense diet in every meal. Aim for low-calorie, high-protein foods while fasting. Incorporate health-promoting foods rich in proteins, healthy fats, and complex carbohydrates.

Prioritize incorporating the following foods during your fast:

• vegetables

• fruits

• whole grains

• dairy

• healthy oils and fats

• lean proteins

Foods to Avoid to Prevent Hindering Your Progress

Remember, eating healthy also means avoiding harmful foods. Not only can they hinder your fasting results but they can also negatively impact your overall health. 

It is crucial to stay away from:

• processed foods

• foods high in sugar

• fried food

• high in salt foods

Stay Hydrated: What You Can Drink While Fasting

Maintaining proper hydration while fasting is paramount for a safe and effective fast. Adequate water levels allow the body to perform essential bodily processes. Fasting often leads to decreased water intake. Adequate hydration is necessary to counterbalance this and ensure optimal body function.

During fasting periods, it is essential to consume only zero-calorie beverages to maintain your body’s fasting state, such as:

• water 

• fruit-infused water (low-calorie fruits like lemon or cucumber)

• herbal teas (no added sugars)

• black coffee (no milk or sweeteners)

• electrolyte-rich drinks (zero-calorie)

Make the Most Out of Your 15-Hour Fast

Uncover how Fastic can simplify your 15:9 fasting journey and master fasting with personalized guidance, progress tracking, and expert advice, all while staying motivated toward your goals.

Disclaimer: It is advised to speak with a health professional before beginning intermittent fasting or a diet program. There may be side effects for people with certain medical conditions.