Eating Windows Vs Fasting Windows
Intermittent fasting is an eating pattern that breaks your day into two parts:
There are actually a variety of intermittent fasting schedules you can follow to determine what hours of the day these windows actually include. We have a handy guide to fasting schedules for you to check out here.
The most common schedule is the 16/8 plan, which means you eat for an 8-hour window and fast for 16 hours. You can also choose to do shorter or longer eating windows, or even opt for alternate-day fasting.
If youre new to this way of eating and need help getting started, definitely check out our Beginners Guide to Intermittent Fasting.
During your fasting period, you want to refrain from consuming any food or beverages that contain calories. So.. no food. But you have several beverage options, and these are important because it is critical to keep yourself hydrated while fasting.
Ways To Use This Information For Better Health
What Is Intermittent Fasting
Intermittent fasting is an eating pattern that alternates periods of eating with periods of either not eating or taking in minimal calories. It emphasizes when you eat rather than what you eat.
Even though it has recently gained mainstream attention, intermittent fasting isnt new. People have practiced periods of fasting throughout history, such as for spiritual, health, or survival reasons .
The intent of intermittent fasting isnt necessarily only to restrict calories, but also to allow your body to focus on maintenance and recovery, rather than digesting.
Many fasting patterns incorporate regular 12- to 16-hour periods of fasting into each day, while others include fasting for 24 or 48 hours once or twice per week.
When you fast, your body undergoes a number of metabolic changes. After some time, fasting causes your body to enter ketosis, a state in which fat is used for energy when carbohydrates are unavailable (
Intermittent fasting rotates periods of fasting and periods of eating. Its often used for health purposes like weight loss and chronic disease prevention, though its been used historically for other reasons.
Will I Lose Weight
Most likely.64 If you have weight to lose, it is extremely likely that you will lose weight if you do not eat.
In theory, its possible to eat more after fasting, of course, cancelling out the weight lost. But studies generally show that most people tend to eat significantly less overall.65
I call intermittent fasting the ancient secret of weight loss because it might be one of the most powerful dietary interventions for weight loss, yet it has been mostly ignored by doctors and dietitians for a long time.66
Can I Exercise During Fasting
However, for long-duration aerobic exercise, eating before exercise may increase performance.39 Its also important to drink fluids and replenish sodium around exercise when fasting. This is good to know if youre competing. Learn more
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Why Should You Fast
First, lets talk about the benefits of fasting. Fasting is a great way to give your system a reset and help your bodys natural processes work more efficientlysuch as energy production, metabolism, and digestive function .
For most people, during the day, youre in the fed state. This means your body is working hard to digest, absorb, and assimilate all the nutrients from the foods you eat. But when you enter a fasted statewhich simply means youre not taking in any caloriesyour body can shift gears and use your energy to focus on the functions that are prioritized after digestion, such as burning fat and boosting metabolism .
This is why the fasted state is often referred to as the fat-burning state. And although you might expect to feel tired or weak without eating, many people experience more energy, less brain fog, and improved focus and concentration when they enter the fasted state.
Intermittent Fasting And Cancer
Although there is little to no literature on the effects of 2 or 3 day fasts on muscle loss in humans, many clinical trials are currently being conducted on the effects of 2 or 3 day fasts on cancer patients.
In initial case studies, people who were undergoing chemotherapy voluntarily fasted for anywhere between 48 to 140 hours. Each person reported fewer side effects and improved quality of life regardless of how long they fasted.
This may suggest that fasting for 2 days to a week can have a protective effect on the cells in the body while they are undergoing intense bouts of toxicity.
Other studies in animals have found that fasting was possibly as effective as chemotherapeutic agents in delaying the progression of different tumors and increased the effectiveness of chemotherapeutic drugs against melanoma, glioma, and breast cancer cells. Although this research may not apply to your life, it does suggest that intermittent fasting can help support your body in times of toxic stress.
Read Also: Is Fasting Good For Your Heart
How Long Can We Last Without Food
Once you start fasting, you may feel ravenously hungry as your mind is flooded with images of your muscles disintegrating into thin air. This is simply how your mind reacts to the threat of starvation just because it feels like you will lose all your muscle and starve doesnt mean you will.
In fact, Mahatma Gandhi survived for 21 days without food while only taking in sips of water. During times when people had no food or water at all, they were able to survive for 10 to 14 days. However, these are just anecdotes what does the science say?
Many studies have been done during hunger strikes and religious fasts confirming that humans have the capacity to survive even longer than Gandhi did during his fast.
One monk, for example, set out to do a 40 day fast with medical supervision while maintaining his daily activities in the monastery. After 36 days, the medical professionals had to step in due to profound weakness and low blood pressure when standing. Although the monk fasted for 15 days longer than Ghandi, the medical professionals were able to stop the fast in time so that he could recover.
Another study tracked 33 political prisoners who were on hunger strike. The prisoners fasted for 6-24 days before being hospitalized for dehydration due an inadequate intake of fluids and electrolytes . Breaking their fast was described as being uncomplicated.
What Else You Should Know
Cost: None beyond your shopping. In fact, because you will eat much less 2 to 4 days per week, your grocery costs should go down.
Support: There are several books and websites detailing variations on the basic idea of fasting a few days a week. So though there’s no single destination for support, there are plenty of resources once you’ve decided which version of the plan appeals most to you.
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What Types Of Blood Tests Require Fasting
The most common types of tests that require fasting include:
- Glucose tests, which measure blood sugar. One type of glucose test is called a glucose tolerance test. For this test you will need to fast for 8 hours before test. When you arrive at the lab or health care facility, you will:
- Have your blood tested
- Drink a special liquid containing glucose
- Have your blood re-tested one hour later, two hours later and possibly three hours later
Glucose tests are used to diagnose diabetes.
- Lipid tests, which measure triglycerides, a type of fat found in the bloodstream, and cholesterol, waxy, fat-like substance found in your blood and every cell of your body. High levels of triglycerides and/or a type of cholesterol, called LDL can put you at risk for heart disease.
Lunch Water Tea & Black Coffee
It doesnt really matter what you drink as long as it doesnt have fats/protein/carbs in it. Caffeinated is fine, but keep in mind that too much caffeine later in the day will interfere with your sleep quality in such a way that your health and dieting progress will suffer.
While I am intermittent fasting, I aim to drink just over a gallon of water a day and drink most of it in between my breakfast and my eating window.
As your kidneys get used to processing the water, and your bladder gets used to the increase in the amount of water youre intaking you wont have to go to the bathroom as much. I know it can be troublesome for the first two weeks to drink that much water, but its extremely good for you to do so, especially while you are adapting to keto.
Also Check: Does Intermittent Fasting Work For Weight Loss
Autophagy: A Nobel Prize Winning Lifestyle Hack
In 2016, the Nobel Prize in Physiology or Medicine was awarded to Yoshinori Ohsumi for discovering some of the mechanisms of autophagy the process by which the cell devours itself. Superficially, this sounds like a terrible thing for our cells to do until you consider what is really taking place.
When our cells undergo the process of autophagy, non-essential parts like damaged proteins are recycled and invading microorganisms and toxic compounds are removed. This means that autophagy plays an important role in stopping the aging process, reversing disease, and preventing cancer, but it doesnt happen all the time.
Fasting, protein restriction, and carbohydrate restriction are the three main ways that can initiate different autophagic processes all of which are not the same. This is part of the reason why a ketogenic diet has so many positive effects, and it also shows you why intermittent fasting is a way to improve your diet even more.
Though this is reason enough to fast more, autophagy isnt the only upside of intermittent fasting. In fact, the combination of keto and fasting can provide us with a wider array of benefits.
‘can I Drink Coffee While Fasting’
I heard the same question almost every time I gave pre-op instructions to a patient: Once I got to the part about nothing to eat or drink after , nearly every one of them would look at me in anguish and ask, Does that mean no coffee??
I feel you.
As a connoisseur of caffeine, myself, I understand that fasting can be difficult enough without giving up coffee to do it. And the good news is: sometimes you dont have to!
The answer to this question depends on the type of fasting youre doing. Can you drink coffee while doing
Pre-surgical fasting? No, you absolutely may not drink coffee after the cut-off time youre given. Thats because the medications used in general anesthesia make it easy for stomach contents to regurgitate into the esophagus, where they can be inhaled. Not good. So, you should never eat or drink anything for several hours prior to a surgery with general anesthesia.
Intermittent fasting? Yes, you can drink black coffee if youre doing intermittent fasting . IF is based on a concept called time-restricted feeding in which you take in calories only during a small window of time each day. But black coffee does not contain calories, so drinking it wont break your fast. Now, if you add cream or sugar, then youve blown your fast because those things contain calories.
Recommended Reading: When Fasting How Many Calories
Best Teas For Intermittent Fasting
The word tea often gets thrown around in a general sense when talking about healthy drinks. But have you ever found yourself staring down the tea selection at your local coffee shop or grocery store aisle and feeling overwhelmed? Us too!
Especially if youre new to tea-drinking, it can be daunting to figure out which type of tea you should choose! We want to help you break it down by highlighting the four types of tea which can be most beneficial to intermittent fasting. Yes, theyre all calorie-free. And weve got both caffeinated teas and herbal teas for you to choose from.
Questions About Exercise And Intermittent Fasting
A lot of people have questions about how to exercise and train while fasting. Here are some good questions that should push you in the right direction with your training.
I wanted to thank you both for writing such a fantastic, motivating blog and for introducing me to intermittent fasting. I am enjoying watching my weight go down by basically doing something that involves no effort skipping breakfast! I was hoping you could elaborate more on your exercise routine. I have waded through the Leangains site and the other links you mentioned in the beginner’s guide, and while very interesting, they are WAY too complex for me at this stage.Paul S.
Readers like Paul are what make our community great. He read about an idea that interested him and even though some of the details were overwhelming, he didn’t let that prevent him from taking action. In other words, he started before he felt ready.
I try to make my writing as easy as possible to use, but it’s always up to you to experiment and see if it makes sense for your circumstances. Keep up the good work, Paul!
Back to the question
Intermittent fasting works great with most strength training programs.
I believe in strength training and compound movements. I think 99% of the population could get in the best shape of their life with only eight exercises: snatch, clean and jerk, squat, bench press, deadlift, pushups, pullups, and sprints. If you did those exercises and did them well, then that’s all you would ever need.
Recommended Reading: Does Fasting Cause Weight Loss
Why Do I Need To Fast Before My Blood Test
If your health care provider has told you to fast before a blood test, it means you should not eat or drink anything, except water, for several hours before your test. When you eat and drink normally, those foods and beverages are absorbed into your bloodstream. That could affect the results of certain types of blood tests.
Dietary Advice Between Fasting Periods
Dear Dr. Fung, I have been following your blog and protocols since last July with much success, and have the Insulin Index paper from Marty Kendall. I look forward to your every post.
What do you suggest about using Whey Protein Powders and what is their impact on insulin? Mark Sisson wrote whey can lower insulin yet often heard is that as a concentrated Dairy, whey protein raises insulin.
I advise against using whey powder for the main reason that it is a highly processed chemical, not a real food. Whey can stimulate insulin, but also is very satiating, so the effect on weight is likely closer to neutral.
Is it necessary to take a multi vitamin on the HFLC or Ketogenic diet?
If you eat a diet predominantly of whole, unprocessed, real foods, then no, it is not necessary.
Seems the rage today is taking care of the gut flora from both probiotics and prebiotics. Are there foods you recommend that help the gut flora. Some diets like Perfect Health Diet recommend safe starches such as potatoes and rice to feed the good bacteria in the gut. Do you personally eat rice or potatoes? Can we get sick from not getting adequate amounts of these safe starches and can you comment on proper care of the gut?
I know that I will ruffle some feathers, but I am quite skeptical about the gut micro biome theory with regards to obesity. So, there are no foods I recommend for that reason alone.
None that I am aware of.
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Whats Next Intermittent Fasting & Keto After The Meal Plan
After youve tried our meal plan, take a moment to assess how it went.
- How did you feel while you were fasting? Were you struggling to make it to your next meal while fantasizing about food or were you able to stay focused throughout the day?
- Does intermittent fasting fit with your schedule and lifestyle better than eating meals throughout the day?
- Is an intermittent fasting schedule a better strategy for you to sustain weight loss than what you were doing before?
Your answers to these questions will provide you with enough info to determine whether or not intermittent fasting is a good dietary strategy for you.
Some people just cant put up with fasting and need to have evenly spaced meals throughout the day, while others experience more energy and focus when they dont have breakfast.
Some keto dieters are able to get incredible results when they use intermittent fasting while others feel worse and dont experience much of a benefit at all.
If you think that intermittent fasting isnt right for you, then theres no need to force it. Just by maintaining a calorie deficit and following the keto diet, you can experience most of the benefits that you would get from intermittent fasting anyway. Follow whatever meal schedule works best for you, and use the principles in our How to Lose Weight on the Keto Diet article to guide you in the right direction.
Isnt Fasting The Same As Reducing Calories
No, not necessarily. Fasting can reduce the time you spend eating and primarily addresses the question of when to eat.62 Calorie reduction addresses the question of what and how much to eat. They are separate issues and should not be confused with each other.
Read Also: What Does Fasting Do To The Body