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Intermittent fasting 101: a science-backed guide to timing meals for better health

This guide provides insights into the numerous health benefits of intermittent, the various ways to do it, and practical tips for getting started.

Health and wellness trends come and go, but intermittent fasting or time-restricted eating—while seemingly a newer trend—has been around for centuries—and for good reason. It’s a powerful approach to improving overall health in many top-of-mind ways—and plenty of science supports it. 

Whether you’re new to intermittent fasting (or IF) or simply want a deeper understanding of what a meal timing adjustment can do for your health, this guide demystifies IF, providing insights into its numerous health benefits, the various ways to do it, and practical tips for getting started.

Understanding Intermittent Fasting

At its core, intermittent fasting involves cycling between periods of eating and fasting. The concept is to extend the time between your last meal of the day and the first meal of the next day, creating distinct fasting and feeding windows. You can tap into various health benefits by staying consistent with only eating for certain hours within your 24-hour clock. 

Yes, IF is probably most talked about for its ability to support weight loss, but the benefits go far beyond body recomposition. It’s also well studied for its anti-inflammatory, gut health, brain-boosting and disease prevention benefits.   

Health Benefits of Intermittent Fasting

Weight Loss: Beyond the scale, intermittent fasting triggers metabolic changes that promote fat loss while preserving lean muscle mass. Research suggests this approach may be more effective than traditional calorie-restricted diets for shedding those stubborn pounds.

Improved Mental Focus: Fasting periods can enhance cognitive function by promoting the production of brain-derived neurotrophic factor (BDNF), a protein associated with cognitive health. Many practitioners report heightened mental clarity and focus during fasting windows.

Gut Health and Digestion: Intermittent fasting allows the digestive system to rest and repair, promoting a healthier gut environment. Fasting can lead to improved digestion, less inflammation in the gut and better nutrient absorption.

Enhanced Sleep Quality: Regular fasting is known to improve sleep patterns. Intermittent fasting positively influences the body's natural circadian rhythm and helps you spend more time in rapid eye movement sleep, contributing to more restful and rejuvenating sleep.

Hormonal Balance: Intermittent fasting can influence hormones like insulin, growth hormone, and norepinephrine, which play crucial roles in metabolism and fat burning. This hormonal balance contributes to overall well-being.

Cellular Repair and Longevity: Fasting initiates autophagy, a cellular recycling process that removes damaged cells and components. This cellular repair mechanism increases longevity and lowers your risk of chronic diseases such as diabetes and heart disease.

Reduced Inflammation: Chronic inflammation is linked to various health issues, including heart disease and diabetes. Intermittent fasting has been shown to reduce inflammation markers in the body, contributing to overall health.


Types of Fasting Methods

16:8 Method: This method is the most common and science-backed and involves a daily fasting window of 16 hours, followed by an eight-hour eating window. It's a beginner-friendly approach that aligns well with most daily schedules and still provides many of the same benefits as more intense fasts.

18:6 Method: Similar to the 16:8 method, this approach extends the fasting window to 18 hours, providing additional benefits for those seeking a more prolonged fasting period, specifically around expediting weight loss.

One Meal a Day (OMAD): OMAD involves consuming all daily calories within a single one-hour meal window. Because it’s pretty hard to overeat in a single hour each day, this method is used for expedited weight loss, but it’s definitely not for everyone—especially those with a history of disordered eating. You can read more about it here.

5:2 Method: This method alternates between regular eating and two non-consecutive days of consuming very few calories (usually around 500-600 calories).

Alternate-Day Fasting: This approach alternates between days of regular eating and days of fasting or consuming minimal calories.

Warrior Diet: This method, which originated from ancient warrior practices, involves consuming small amounts of raw fruits and vegetables during the day and one large meal at night.

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How to Ease Into Intermittent Fasting

Experts recommend starting an intermittent fasting regimen gradually to allow your body to adjust. Start with a shorter fasting window, such as 12 hours, and incrementally extend it as your body adapts. Listen to your body's signals, stay hydrated, and focus on nutrient-dense meals during your eating windows. 

What Breaks a Fast?

There’s some debate around this, but most intermittent fasting experts will say any caloric intake breaks a fast. Yes, even a 15-calorie splash of milk in your coffee. Fast breakers include foods and beverages with calories. The exception is water, black coffee, or plain tea. 

The primary goal of intermittent fasting is to extend the fasting period, allowing the body to enter a state of ketosis and promoting the health benefits mentioned above. Consuming even small amounts of calories during the fasting window can interrupt this process and negate some of the intended effects. 

Fasting Safely 

Before diving into IF, it's a good idea to consult with a healthcare professional, especially if you have pre-existing medical conditions. Pregnant or breastfeeding women, individuals with a history of eating disorders, and those with certain medical conditions may need to approach intermittent fasting with caution or avoid it altogether.

Common Challenges & Solutions

While IF offers numerous benefits, challenges may arise, including hunger, social situations, and fatigue. To combat hunger, stay hydrated and include fibre-rich foods in your meals. Manage social situations by planning or being transparent about your fasting schedule, combat fatigue with adequate sleep, eat nutrient-dense meals, and adjust your fasting window if necessary.

Tips for Success

Successful intermittent fasting requires careful planning and attention to your body's signals. For instance, if you’re ravenous but still in your fasting window, no hard rule says you must complete the whole 16- or 18-hour fast no matter what. 

Some days, you must listen to your body and break your fast early. For women, hormonal fluctuations throughout the month may play a role, as one example. Not every day will be a perfect fasting day, but what amounts to a whole over time is what matters. 

Plan meals in advance, ensure a balanced intake of nutrients, incorporate regular exercise, and track your progress. Remember, intermittent fasting is a personal journey, so adjust your approach based on what works best for you.

About the Author


Alicia is a journalist and editor in digital and print media specializing in health, nutrition, fitness, and wellness. She was previously the Editorial Director of Clean Eating and Vegetarian Times. Her work has also appeared in Hone Health The Edge, Yoga Journal, Women’s Running, and Oxygen, among others. In addition to being a content creator, she's an ISSA-certified nutritionist, certified personal trainer, and fitness studio owner in Toronto. Alicia loves spreading the word about helpful, science-backed health information, and she can be contacted via her website at