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What Happens To Your Body During Intermittent Fasting

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May Be Beneficial For Heart Health

What Really Happens When We Fast?

Heart disease is currently the worlds biggest killer .

Its known that various health markers are associated with either an increased or decreased risk of heart disease.

Intermittent fasting has been shown to improve numerous different risk factors, including:

  • blood sugar levels

The effects of fasting on heart health need to be studied more in-depth in humans before recommendations can be made.


Studies show that intermittent fasting can improve numerous risk factors for heart disease, such as blood pressure, cholesterol levels, triglycerides, and inflammatory markers.

This Is Your Body On Intermittent Fasting

Its no surprise that intermittent fasting is one of the most popular types of eating plans. You dont need to measure out food or buy any prepackaged shakes. There are no required weigh-ins or calorie counting. All you really have to do is not eat during certain hours. Its pretty simple.

There are different ways to go about it, of course. Most people do the 16:8 diet, in which you fast for 16 hours and then eat within an eight-hour window. Theres also the 5:2 diet, where you drastically cut back on calories just two days a week, and there are 24-hour fasts, where you dont eat anything one day each month.

Regardless of the method, significantly restricting when you eat can throw your body for a loop and cause a handful of odd side effects. Intermittent fasting may not be suitable for everyone.

Its important to know what to expect before you jump into any new eating habit. Heres what happens to you mentally, physically and emotionally when youre fasting intermittently.

Intermittent Fasting Cycles Between Periods Of Reduced Or Zero Calorie Intake And Periods Of Unrestricted Eating

Intermittent fasting cycles between periods of reduced or zero calorie intake and periods of unrestricted eating.

But there are also other approaches to intermittent fasting, such as the 5:2 Diet, which involves eating normally for 5 days of the week while restricting calories to 500-600 on two days of the week, or the Eat-Stop-Eat method which involves doing a 24-hour fast once a week .

Despite many of us being familiar with intermittent fasting, most people are in the dark about what happens to the body when they do it.

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Fasting Stage #: Postabsorptive Phase

The second stage of fasting, according to Cahill, is the post-absorptive phase.

During this four to 16 hours after eating, the body digests the ingested food energy. However, during this process, insulin levels begin to fall again.

Although most cells still use glucose for fuel, it now comes from glycogen stores rather than directly from food .

Because the liver breaks glycogen back down into glucose, it can be transported throughout the body via the bloodstream.

The capacity of these carbohydrate stores depends on stature and body size. Therefore, they cover almost precisely the individual daily requirement of each person.

However, if you eat a low-carbohydrate diet, the glycogen stores will not be full. Consequently, the body can fall back on stored fat even earlier.

Like fasting, therefore, ketogenic diets aim to lower insulin levels.

Since high insulin levels are a significant risk factor for chronic diseases, the post-absorptive fasting stage is enormously essential.

  • Human growth hormone

Thus, these hormones signal the body to mobilize energy from glycogen and fat stores.

While growth hormone ensures that the body can build and repair cells, the other hormones ensure an increased basal metabolic rate .

Tips To Increase Success Of Intermittent Fasting Breaks

The Benefits Of Fasting

That said, there are a few things you can try to increase your success in quitting intermittent fasting well intermittently.

They are:

  • Consider fasting longer on days when youre on program to compensate for the breaks. So if every Friday you know youre going off-plan, shoot for a 20-hour fast before Friday, then after Friday skip breakfast and lunch Saturday. More fasting hours is better.
  • Postpone this until youre stable. If at all possible, give yourself about a month of tried-and-true fasting full-out. If you can break from intermittent fasting on schedule after youve already seen good results, itll be easier to stick with it.
  • Reduce your fasting window on those days dont eliminate it. Commit to still fasting 12 hours on your off days. Twelve hours is still enough to see results.
  • Eat as clean as possible. You should aim for that anyway, but its worth repeating here.

Recommended Reading: What Foods Should I Eat While Intermittent Fasting

Is Intermittent Fasting A Sustainable Way To Lose Weight

There are also downsides to intermittent fasting. Not all fasting regimes are beneficial and for some, it may lead to headaches, problems concentrating, irritability and feeling faint and tired. It can also be easy to overeat during non-fasting periods too. This is because the hormones linked to appetite and hunger can go into overdrive when you are deprived of food.

It may also be more beneficial to concentrate on eating a balanced diet with plenty of fibre, fruit and vegetables, rather than fasting. One diet is not right for everyone and the diet may not be sustainable, says Hall. There is a lack of long-term studies at present and smaller healthy changes may be more sustainable than a restricted diet.

Additionally, recent research has suggested that the time in which you eat may be more important than the time spent fasting. Earlier this year, researchers at Northwestern University discovered those who started eating before 8:30 am had lower blood sugar levels and less insulin resistance, which could reduce the risk of developing type 2 diabetes.

Its also important to note that intermittent fasting can lead to an unhealthy focus on diet and eating habits too. It can be easy for diet regimes to become all-encompassing, which can lead to disordered eating and anxiety. For those who have a history of eating disorders, any restrictive diet may be triggering for an eating disorder recurrence, says Hall.

Intermittent Fasting: The Latest Research

Jennifer Aniston says it changed her life. No, were not talking about a sitcom. Were talking about the current trending diet of intermittent fasting. But before you dismiss it as just a fad, Jeffrey Hooper, MD, says for some people intermittent fasting has real benefits that may go beyond weight loss.

Its not new, says Dr. Hooper, medical director for the MultiCare Center for Weight Loss & Wellness. Like so many things in weight loss, the pendulum swings, and intermittent fasting is getting popular again.

And because its been around for a while, intermittent fasting actually has science behind it, he adds.

In late December, the New England Journal of Medicine published an article reviewing previous intermittent fasting studies, giving the method another big publicity boost.

The review highlighted findings that, along with promoting weight loss, intermittent fasting decreases insulin resistance and the chances of developing diabetes, reduces risk for some cancers and forms of dementia and increases cardiovascular health and stress resistance. Studies in rats showed that intermittent fasting greatly increased their lifespans and slowed the aging process.

A lot of these things are connected to weight loss, but others are less related, Dr. Hooper says. Theres benefit from doing this that goes beyond just the weight loss effect.

For some people, thats a really attractive extra, Dr. Hooper says.

Some adults also seem to do better when they eat soon after waking.

Also Check: How To Start Fasting For Health

Ways To Use This Information For Better Health

  • Avoid sugars and refined grains. Instead, eat fruits, vegetables, beans, lentils, whole grains, lean proteins, and healthy fats .
  • Let your body burn fat between meals. Dont snack. Be active throughout your day. Build muscle tone.
  • Consider a simple form of intermittent fasting. Limit the hours of the day when you eat, and for best effect, make it earlier in the day .
  • Avoid snacking or eating at nighttime, all the time.
  • What Does It Mean When You Say Intermittent Fasting


    Feel free to jump straight to the one youre really after. So scroll down and lets get it started! Intermittent fasting is an action of fasting intermittently. It is an eating pattern where you cycle between periods of eating and periods of voluntary fasting over the course of the single day, week or other defined period. Huh?

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    Sleep More Eat Healthier

    Adults need at least 7 hours of sleep a night for optimal health, according to the American Academy of Sleep Medicine and the Sleep Research Society. But most fall short, and that can influence eating habits and metabolism.

    In one study, 16 people slept for 9 hours a night for five days , then switched to 5 hours a night for five days.

    Sleeping just 5 hours disrupted their circadian rhythm, which led them to take in excess calories, gain weight, and experience an almost 20 percent drop in insulin sensitivity.

    Insufficient sleep seems to prompt evening eating, McHill says. And its those calories that seem to account for the weight gain and metabolic issues.

    What you eat can also disrupt sleep. Consuming spicy foods close to bedtime may upset your digestive system, and caffeine may delay the onset of melatonin. Research also suggests that eating lots of added sugars and processed grains may trigger insomnia, while eating more vegetables and fruit may help prevent it.

    Editors Note: A version of this article also appeared in the April 2021 issue of Consumer Reports On Health.

    Jennifer Cook

    Jennifer Cook is an award-winning freelance writer who contributes to Consumer Reports on health, wellness, mind-body, and environmental topics. She lives in New York’s Hudson Valley in a farmhouse built in the 1840s. An avid walker and dancer, she feels fortunate to live near wetlands and wild things, and to have easy access to culture and good food.

    The Hour By Hour Benefits Of Intermittent Fasting

    We all naturally fast or take a break from eating for at least 8 hours a day. Its when were asleep!

    The prevailing view has always been to start your day with a hearty breakfast but recent research suggests that taking a longer break can help you lose weight and improve overall health. Its a movement that has gained popularity but it is also evidence based with research continuing to show its benefits.

    Whether you call it intermittent fasting or time-restricted eating, it involves intentionally taking a break from eating for anywhere from 12 to 16 hours a day.

    Intermittent Fasting has been shown to:

    Lower Insulin Levels

    Increase Fat Burning,

    Help with Cellular Regeneration

    Also, it stands to reason that if youre eating for fewer hours a day, theres a good chance youre eating less overall, helping to lose weight if thats a goal.

    Pretty impressive huh?

    And its not nearly as hard as you think.

    There are numerous health benefits related to intermittent fasting including:

    • Weight and body fat loss. …

    • Increased fat burning. …

    • Lowered blood insulin and sugar levels. …

    • Possible improved mental clarity and concentration. …

    • Possible increased energy. …

    • Possible increased growth hormone, at least in the short term

    Heres a breakdown of what you body does each hour of fasting :

    4-8 hours

    • All food has left the stomach

    • Insulin is no longer produced

    12 hours

    14 hours

    16 hours

    • Body starts to ramp up the fat burning

    18 hours

    24 hours

    36 hours

    72 hours

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    Path To Improved Health

    Intermittent fasting is not a diet plan. While it may have some of the same health benefits as a diet, its really an eating pattern. It means you fast during a certain period of time each day . You then eat during another period of time each day . While youre fasting, you can drink beverages that dont contain calories, including water, black coffee, and unsweetened tea.

    How fasting and eating is divided each day is called an eating schedule. One of the most common, easy-to-follow schedules is 16:8. This means you fast for a 16-hour period of time and eat your daily meals during an 8-hour period of time. For example, you may want to fast from 7 p.m. until 11 a.m. the next day. You would then eat a healthy lunch and dinner between 11 a.m. and 7 p.m. You wouldnt eat anything after 7 p.m. until 11 a.m. the next day. This is just an example of times. You can select any 16-hour and 8-hour block of time that works best for your schedule. But its important to keep your eating window at the same every day.

    Intermittent Fasting Can Help Weight Loss

    What happens to your body during Intermittent Fasting ...

    IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains , are quickly broken down into sugar, which our cells use for energy. If our cells dont use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.

    Between meals, as long as we dont snack, our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. We lose weight if we let our insulin levels go down. The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.

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    Autophagy Begins & Inflammation Decreases

    With the chore of digestion behind us, resources are diverted toward clean-up processes like autophagy, which removes damaged cells and debris.

    There is also a reduction in inflammation that occurs throughout the body as well as an increase in the secretion of metabolic hormones, including growth hormone and norepinephrine, which helps to support your metabolism as your day of fasting comes to a close.

    Intermittent Fasting Schedules To Follow

    There are many ways to practice intermittent fasting for weight loss. The following are some of the most popular schedules:

    Time-restricted eating: This involves consuming all of your meals within a period of 4-12 hours in a day. For example, you could choose to have your meals and calories between 8 am and 6 pm. Limiting your calorie intake to daylight hours is called eating with the sun. Time-restricted eating is particularly beneficial if you eat your meals before sunset. Not only does this help you eliminate bad habits like late-night snacking, but it improves your sleep and blood sugar control. Over time, time-restricted eating can lower your blood sugar levels, make you more sensitive to insulin, and reduce your blood pressure.

    One-meal-a-day : This involves packing all of your days calories in a single meal that you consume within 1-2 hours. A small study conducted by Dr. Jason Fungs research group showed that fasting for 24 hours 3 times a week and eating only dinner on fasting days, eliminated the need for insulin in type-2 diabetic patients. This fasting approach also resulted in improved HbA1C, lower body mass index, and reduced waist circumference.

    What intermittent fasting schedule is right for you? Find out here.

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    So Is Intermittent Fasting As Good As It Sounds

    I was very curious about this, so I asked the opinion of metabolic expert Dr. Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School. Here is what she told me. There is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10-hour period of the daytime, is effective, she confirmed, though generally she recommends that people use an eating approach that works for them and is sustainable to them.

    So, heres the deal. There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially for people at risk for diabetes.

    Read Also: Is Intermittent Fasting Good To Lose Weight

    Making The Most Out Of Your Fast

    Intermittent Fasting | What Happens Inside Your Body Over Time

    Fasting isn’t always easy to get used to. That’s why when you fast, you should do these five things to get the most benefit out of every minute that has passed without food!

  • Stay hydrated: This is the golden rule of fasting. Not only is going without water harmful to your health, but it will make your energy levels plummet and the minutes will drag by. Try these drinks to stay hydrated and shake up your “drink menu” on fasting days.
  • Rest and relax: Plan your workout schedule around fasting, don’t try to do too much at once. You can easily become dehydrated, lightheaded, and exhausted after a fasted workout if you’re not used to it. Don’t ask too much of your body during fasting days, keep it light. Try yoga and walking to stay active so you wonât crash or need to break your fast.
  • Eat high-volume food: If you’re following an intermittent fasting plan that allows food consumption on fasting days aim to eat high-volume, low-calorie, nutrient-dense foods, or foods that “take up a lot of space” and help you to feel full. High-volume, low-cal foods include leafy greens, broccoli, melon, apples, oatmeal, air-popped popcorn, brown rice, beans, eggs, and fish.
  • Increase the taste: Every calorie counts when you’re fasting, so enjoy them! Eating healthy yet flavorful foods you love during the eating periods of your fast can help give you the mental push you need to go on. Try eating the foods mentioned above and go heavy on the spices! Healthy, filling food doesn’t have to be bland.
  • Read Also: How To Succeed At Intermittent Fasting

    Accelerate The Stages Of Intermittent Fasting With Keto

    Based on these five stages of fasting, you can decide for yourself how long the intermittent should last for your health goals.

    However, if you want faster and more efficient results, you can combine intermittent fasting with the keto diet.

    Like fasting, the keto diet aims to deplete glycogen stores and tap into body fat for energy.

    If youre already in ketosis at the beginning of the fast, youll have a clear starting advantage. This way, you dont have to consume glycogen for 1-2 days before burning fat efficiently.

    Furthermore, a keto diet helps suppress hunger and protects against side effects such as headaches .

    Finally, the body is not deprived of sugar for the first time during this process, making the stages of fasting much more convenient.

    Additionally, the combination of keto and intermittent fasting offers even more health benefits.

    Suppose youre fasting for an extended period. In that case, its crucial to break the fast with a meal that returns the proper nutrients to the body while not overwhelming the gastrointestinal tract:

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