Intermittent fasting is rapidly becoming one of the world’s most popular health and wellness trends. Many celebrities sing its praises, citing its health benefits and ease of use. But they aren’t the only ones. In fact, millions of people around the world now use this ancient way of eating to lose weight, improve health, and even live longer. In this guide, we’ll explore all facets of intermittent fasting, including its history, advantages, options, rules, and the stages of the fasting process. Read on to learn more.
What is Intermittent Fasting?
Simply put, fasting means you stop eating or stop eating almost completely for a certain amount of time. Furthermore, intermittent fasting (IF) is an eating schedule, which alternates between periods of little to no food and times in which you’re allowed to eat. Typically, when on an IF diet for weight loss, all calories consumed must be made up of ‘good’ foods, like vegetables or whole grains during designated hours of the day. This type of fasting can help regulate blood sugar levels and boost metabolism by burning more fat than usual. Additionally, fasting can help promote better brain function and protein-sparing weight loss, which could even help prevent cancer.
It’s Nothing New
Though fasting has seen a recent surge in popularity, it’s been around since at least the 5th century BCE when Greek physician, Hippocrates, recommended it to patients with certain illnesses. Additionally, humans have used fasting as a form of therapy to treat diseases like obesity and diabetes as early as the 1900s. But humans aren’t the only ones who benefit from this way of eating. In fact, fasting is part of the life cycle for many living organisms. Often, animals undergo periods of food deprivation to survive, including hibernation and migration.
Advantages of Intermittent Fasting
IF is an ancient practice with roots in many cultures and religions across the world. However, it continues to gain more attention as research uncovers more of its health and wellness benefits. Here are just a few of the possible advantages of IF:
- Weight loss and increased metabolism
- Improved blood sugar control
- Decreased inflammation
- Improved attention
- Enhanced heart health
- Improved mood
- Reduced risk for chronic diseases
- Neurodegenerative disorder prevention
- Improved mental clarity
- Increased focus/concentration
- Improved memory
- Cancer prevention and increased chemotherapy effectiveness
- Improved reasoning
- Extended lifespan
So, what happens inside your body as it goes through as it transitions from ‘feeding to fasting’? Here are the five stages of metabolism and fasting:
- Feeding (Eating) Phase: During this time, blood sugar and insulin rise. When we eat, glucose is created in our digestive system and the body converts it to glycogen. Our liver has enough storage for around 100 grams of this carbohydrate. But, if there’s more than that available, the body will convert the excess into fat cells.
- Postabsorptive Phase (6 to 24 hours after beginning a fast): During this phase, blood sugar and insulin decrease. Also, glycogen breaks down, releasing glucose (glycogen storage lasts for 24 to 36 hours). As a result, the released glucose provides instant fuel for muscles, working at high-intensity levels like when sprinting up a hill.
- Gluconeogenesis Phase (24 hours to 2 days after beginning a fast): In this stage, the body’s glycogen stores have run out. So, the body manufactures new glucose from recycled essential fats and amino acids. Glucose levels fall but stay within a normal range.
- Ketosis (2 to 3 days after starting a fast): During this stage, lowered insulin levels stimulate lipolysis (breakdown of fat for energy). Then, fat cells release fat in response to low insulin levels. As a result, the body uses more energy.
- Protein Conservation Phase (5 days after beginning a fast): In this phase, high levels of growth hormone maintain muscle mass and lean tissue. Therefore, fatty acids and ketones supply nearly all the energy needed for basic metabolism.
Basically, these stages cumulatively trigger the body to start using stored fat for energy instead of its preferred energy source, glucose. Additionally, the increased growth hormone levels help to ensure muscle tissue is preserved during fasting.
There is No ‘Right’ Way to Fast
There isn’t just one way to fast or even a preferred IF regiment. In fact, there are many types of IF, all with a unique style. Additionally, each style carries its own benefits – from boosting metabolism, promoting disease prevention or cellular repair, to improving psychological wellbeing. Some evidence shows eating earlier (noon to 4p) may be better for weight loss than later in the day. Typically, the longer the fast, the greater the benefit. However, fasting for prolonged periods of more than 24 hours with no food is not recommended, as it may lead to cognitive side effects like depression or anxiety due to decreased levels of serotonin production (which regulates sleep cycles).
Types of Intermittent Fasting
Below is a brief description of multiple IF options:
- The 5:2 Fast: Many use this method to kick-start a fasting regiment. It includes eating normally 5 days per week and decreasing to 500-600 calories per day for the remaining two.
- Alternate Day Fast: Basically, this method includes fasting every other day.
- 12-Hour Fast: A beginner favorite, this method still allows for 3 meals per day and isn’t as restrictive as other methods. For example, you may choose to fast between 7 p.m. and 7 a.m., which means you would finish dinner by 7 p.m. and start breakfast after 7 a.m.
- The 16/8 Fast: The method involves fasting every day for 16 hours. So, your daily eating window will be around 8 hours, typically 2 meals per day. Usually, the 16-hour fasting time includes hours you are asleep.
- Eat-Stop-Eat (20-24 Hour) Fast: A 20 to 24 hour period, typically lasting from dinner to dinner or breakfast to breakfast. Often, this also allows for 1 small meal a day, especially for those with medications requiring food.
- 36-Hour Fast: Simply put, this involves fasting for a 36-hour period. For example, Day 1: Dinner at 7 p.m., Day 2: No meals, Day 3: Breakfast at 7 a.m. This method is typically recommended for those who have experience with fasting and have built up to 36-hours.
- Extended Fasting: Extended fasting refers to fasting for more than 36 hours and up to 14 days. This method leaves intermittent fasting behind, entering its own category. For that reason, we again recommend starting slow with overnight fasts and gradually working your way up. This type of fast requires homemade bone broth and/or multivitamins for the balance of vitamins and minerals.
Permitted Food & Beverages
Though most foods and beverages are restricted during fasting, there are a few items that are permitted. Only the following are allowed for consumption during the ‘fasting window’:
- Water (plain or sparkling)
- Tea (ideally green tea)
- Black coffee (no more than six cups/day)
- 1-2 teaspoons of coconut oil or cinnamon are typically allowed, yet technically not part of a true fast
- Medium-chain triglyceride oil
- Homemade bone broth
- Sea salt
The Bottom Line
In closing, IF’s popularity is on the rise for a reason. Fasting is not only a simple and effective method of losing weight. It can also provide a wealth of other health benefits for the mind and body. However, it is not for everyone. Always check with your doctor first to make sure IF is right for you. Also, consider starting slowly with a 12-hour overnight fast to ease into your journey to improving your overall health and wellbeing.
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