What is intermittent fasting?
Have you heard of IF? If weight loss programs based on intermittent fasting are crowding your news feed as they are mine, maybe you’ve scrolled past thinking: that sounds awful…. Or maybe you were intrigued.
When most people hear the phrase “intermittent fasting” they recognize it as a diet. Or maybe something that sounds a little bit like starvation. It is actually not a diet at all, but more of an intentional eating pattern and ideally, it’s not to be accompanied by excessive hunger. The stereotypical word “diet” indicates a set of rules and guidance for foods you should and should not eat whereas intermittent fasting is a method to dictate when you eat. Intermittent fasting simply means eating intentionally within a certain window of time and fasting when that window is closed. In fact, it’s something we do each night while we sleep, but there are several more methods gaining traction for their health benefits.
Types of Fasting
- Water fasting: The only thing you consume during the fast is water.
- Water + non-caloric beverages: The only things you consume are water and non-caloric beverages like plain tea and black coffee. Adding milk, sugar, sweeteners, or artificial sweeteners could impact your blood sugar levels or insulin.
- Fat fasting: Fat fasting allows for water, non-caloric beverages, and healthy fats. For most people. the body’s insulin response to dietary fat is very small and insignificant. Because of this, adding dietary fat into the fast still provides many benefits of a fast and can make the fasting experience less stressful, especially at first. (We are all different. Some people have a more significant insulin response to some types of fat, so you might want to check your own insulin response to specific foods!)
Popular Intermittent Fasting Protocols
Below are some of the most common intermittent fasting protocols.
Circadian Rhythm Fasting
Based on Dr. Satchin Panda’s research, you would start fasting as close to sunset as possible for at least 13 hours.
The 16/8 Method
Restrict your daily eating period to 8 hours and fast for the 16 hours in between. For example, begin eating window at 9:00AM and stop eating or end window at 4:00PM. Another example would be to begin eating at 12:00PM and stop eating at 8:00PM, but it can flex to whenever is most convenient.
24 Hour Method
Fast for 24 hours, once or twice each week. For example, stop eating at 6:00PM and don’t eat again until 6:00PM the next day.
The 5:2 Method
For two days of the week, eat 500-600 calories. Eat normally the other 5 days. Be sure that the two low calorie days are non-consecutive days.
The Fast 5
Eating within 5 consecutive hours, and fasting for the other 19 hours. Popularized by Dr. Bert Herring.
Fast every other day by consuming no calories during your fasting days and eating normally the other days. If this feels extreme at first, try eating only 100-500 calories on fasting days and work up to 0 calorie fasting days. For example, you could choose to eat part of an avocado or add coconut or MCT oil to your tea, as the overall goal is to keep insulin levels untouched by the food intake.
Popularized by Dr. Jason Fung, the author of The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting.
Fast during the day, and have one large meal every night. Alternatively, you can have small amounts of vegetables and fruits during the day and have a large meal at night.
Skip 1-2 meals when you aren’t hungry or don’t have time to eat. This method is less structured but will likely feel the most natural. Not for someone who wants to start intermittent fasting and likes structure.
Why would you do it? Benefits of Intermittent Fasting
It is effective for weight loss.
At this point, we all know that calories aren’t everything. Caloric quality is just as (or more) important as caloric quantity. That doesn’t mean that calories don’t count – a caloric deficit can still work for weight loss in many people. Intermittent fasting gives structure to your eating pattern and allows you to consume your food in a shorter time period. This might make it easier for you to consume less calories than you would have in a longer time period.
When trying to lose weight and burn fat, lowering your blood sugar is important to avoid pre-diabetes, diabetes, insulin resistance and most importantly becoming overweight. If your goal is weight loss or fat burning, you should consider lowering your blood sugar to avoid conditions like pre-diabetes, diabetes, and insulin resistance. These conditions are obviously poor for your health, but can also lead to weight gain! Intermittent fasting causes lower insulin levels, higher growth hormone levels (which are associated with weight loss) and higher amounts of norepinephrine (a neurotransmitter that is released from the sympathetic nervous system in response to stress) in the body. Intermittent fasting can even improve your insulin sensitivity.
“Insulin sensitivity is the relationship between how much insulin needs to be produced in order to deposit a certain amount of glucose. You are insulin sensitive if a small amount of insulin needs to be secreted to deposit a certain amount of glucose, and insulin resistant if a lot of insulin needs to be secreted to deposit the same amount of glucose.“
It allows you to burn fat as fuel.
What is fat oxidation? It is your body’s ability to use stored fat for energy or fuel. Intermittent fasting enhances hormone function to facilitate fat loss and allows that fat to be used for energy. In other words, your body is more likely to use stored fat for fuel closer to the end of your fasting hours.
It is effective for weight maintenance.
Using similar logic that applies to weight loss, it is easier to maintain your weight once you have the structure of a shorter eating window and a longer fasting window. The structure of intermittent fasting allows for more predictable digestion, which is great for weight maintenance!
Reduce inflammation in the body.
Oxidative stress and inflammation are two of the top drivers of aging–like wrinkles and chronic illness, like cancer. Intermittent fasting can both reduce inflammation and enhance your body’s resistance oxidative stress in the body.
It facilitates cellular repair in the body.
Intermittent fasting turns on a process in the body called autophagy. Autophagy is the body’s way of “taking out the trash” the cells in the body initiate a cellular “waste removal.” Autophagy maintains the body’s homeostasis by protein degradation and turnover of the destroyed cell organelles for the formation of new cells.
It is simple & time efficient.
Less meal prep. Less packing. Less eating. For example, if you chose to follow the 16/8 method, you would likely be eating two large meals instead of three. Not only is that one less meal to prep, but it’s one less meal you have to sit down and eat! Imagine what you could accomplish with that time! If you’re doing a 24 hour fast, that’s even more time you get to reclaim for your day!
It is cost effective.
Imagine going to the food store and not having to buy food for breakfast! Following the 16/8 method? If you’re eating between the hours of 12:00PM – 8:00PM, then you only need to purchase food for two meals instead of three.
Busting Common Myths
- Fasting is NOT starvation!
It is common for people to believe that if you refrain from eating for an extended period of time, your body will hold onto body fat instead of using it for energy. Shifting away from thinking about calories and leaning into more whole foods and relying on healthy fats like avocado, coconut oil, and olive oil can promote fullness and improve the benefits of fasting.
“Starvation mode actually is guaranteed if you just try and cut your calories. But what’s interesting is that fasting doesn’t do that. What happens during fasting is that … after four days of fasting, the basal metabolic rate is actually 10 percent higher than when you started. The body has not shut down at all. In fact, what it’s done is it switched fuel sources. It switched from burning food to burning [body] fat. Once it’s burning [body] fat, it’s like, ‘Hey, there’s plenty of this stuff. Let’s burn our 2,000 calories’…”
- Fasting will NOT lead to a decrease in muscle mass.
Contrary to popular belief, the human body responds to fasting by downregulating protein catabolism and upregulating growth hormones.
“If you follow the biochemistry, your body stores energy as glycogen in the liver, which is links or chains of sugar, and then it stores [it as] body fat. During fasting, you start by burning off all the glycogen in the liver, which is all the sugar. There’s a point there where some of the excess amino acids in your body need to get burnt as well. That’s where people say, ‘That’s where you’re burning muscle.’ That’s not actually what happens. The body never upregulates its protein catabolism. Never is it burning muscle; there’s a normal turnover that goes on. There is a certain amount of protein that you need for a regular turnover. When you start fasting, that starts to go down and then fat oxidation goes way up. In essence, what you’ve done is you switched over from burning sugar to burning fat. Once you start burning fat, there’s almost an unlimited amount of calories there. You could go for days and days.”
Some research shows that intermittent fasting alone may not decrease your body fat percentage, but when the fasting is paired with resistance training, lean mass can be retained and/or enhanced.
Frequently Asked Questions
- Is there anyone that shouldn’t intermittent fast?
Some women have experienced hormonal changes that lead to amenorrhea. Amenorrhea is the loss of a woman’s menstrual cycle for 3 consecutive cycles. Women can intermittent fast but should be on the lookout for abnormalities with their menstrual cycle. Start small and listen to your body. If it doesn’t feel right, assess your IF strategies and adjust accordingly. If it does feel right, continue with a watchful eye! Individuals with a history of eating disorders or disordered eating should probably steer clear from intermittent fasting as well. Women trying to conceive may not benefit from intermittent fasting and should discuss this with their provider.
- What can I drink during my fasting period?
Non-caloric beverages like water, coffee, and tea are fine during the fasting period. If you can’t go without adding a small amount of cream to your coffee, that is fine, but be sure to not add any sugar to your coffee unless you want to spike your insulin and negate the positive effects of lower blood glucose.
- Can I take supplements during the fasting period?
Yes, non-caloric supplements are fine during the fasting period. It is important to note that fat soluble vitamins are better absorbed when consumed with fat. If you are taking a fat soluble vitamin supplement, you might want to consider taking it with fat-containing foods.
- Is exercise okay?
YES, absolutely! Exercising in a fasted state might even encourage your body to burn fat for fuel. That being said, listen to your body. If exercising during a fast doesn’t feel right, don’t do it!
Tips & Tricks
- No need to start with a 24 or 48 hour fast! There’s nothing wrong with starting out doing a daily 12-14 hour fast and working your way up to a longer fast once you determine if it is right for you. Starting small allows you to determine what works for you without feeling overwhelmed or stressed out.
Stay busy during your fasting hours – or sleep!
- Don’t give yourself time to think about the hunger. My favorite time to fast is during work because I am so busy that I don’t have much time to eat anyway.
- Sleep during the hardest hours of the fast. After some trial and error, you might find that fasting during certain times of the day doesn’t work well for you. Readjust your hours so that during the times that fasting is the hardest, you are asleep! The best part about intermittent fasting is that it is truly customizable to everyone.
Remember to track your results.
- Tracking nutrients, results, and reflections look different for everyone. While tracking is not necessary to see the benefits of intermittent fasting, it is useful to see what works and what doesn’t work for you – because you are an individual! What works for someone else might not work for you. Tracking your self-experimentations will allow you to make adjustments until you find what works for you.
- If you need help tracking your fasting, you can check out the app Zero. This app allows you to choose your type of intermittent fasting, keep track of your progress, and export your data.
You might get some strange looks or a lot of questions.
- I was listening to the Rich Roll Podcast, an episode with Ray Cronise, and he was discussing the difference between biological and social extremes. While fasting is not biologically extreme (our bodies are smart and know what to do in times of feast and famine) it is considered socially extreme. When you first tell people that you are intermittent fasting, you might get some strange looks and questions. After about a hundred of those, you will start to anticipate them. Being different is awesome! Embrace it and know that you are doing something great to benefit your health. Share the knowledge, maybe they will want to try it or will at the very least learn something!
Give it time.
- Intermittent fasting is not the way you’ll lose 1lb/day or 3lb/week! You might have some ebb and flow and the initial weight you’re dropping might be retained water from certain foods you were eating in the first place. Expect some ups and downs and focus on feeling your best. Proper intermittent fasting can help you lose body fat, maintain your weight, and increase your health-span, but not in the blink of an eye! Be patient, listen to your body, and make intentional choices. You’ll get there, I promise!
Last but not least, don’t over complicate it!
- If you’re searching the web and reading about other people’s intermittent fasting experiences, you might be overwhelmed by how technical it can get and how complicated it seems. It doesn’t have to be that way! Simply put – sometimes you eat, and sometimes you don’t. Don’t stress about the numbers if you eat an hour sooner or later than you planned. 15 and 17 hours is not that much different than 16 hours. Intermittent fasting is not just about the numbers! That being said, if you like geeking out over the numbers, there is tons of opportunity for that too.
This article does not take the place of tailored advice from your healthcare professional.
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