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How Is Intermittent Fasting Healthy

Intermittent Fasting Side Effects To Watch Out For

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Over the last several years, intermittent fasting has become increasingly popular for its promises of improved health and weight control. The idea is that it’s easier to sharply restrict calories a few days a week or to limit eating to a shortened “eating window” each day than it is to moderately cut calories at every meal, every day.

Proponents claim that extended fasting periods promote cellular repair, improve insulin sensitivity, increase levels of human growth hormone, and alter gene expression in a way that promotes longevity and disease protection. But are there any risks?

Before weighing intermittent fasting side effects, it’s important to know that there are several forms of intermittent fasting, and the evidence of their long-term effectiveness and safety is not yet known. The most common forms include:

  • Alternate day fasting , which requires fasting every other day
  • Modified alternate-day fasting, which requires you to only eat 25 percent of your usual intake every other day
  • Periodic fasting, which requires you to limit food to about 500 to 600 calories a day on only two days per week
  • Time-restricted eating, which limits your daily “eating window”

Some plans may cause more side effects than others, but overall, it’s important to discuss the following intermittent fasting side effects with a medical professional before choosing a plan that works with your lifestyle.

Safety And Side Effects

Hunger is the main side effect of intermittent fasting.

You may also feel weak and your brain may not perform as well as youre used to.

This may only be temporary, as it can take some time for your body to adapt to the new meal schedule.

If you have a medical condition, you should consult with your doctor before trying intermittent fasting.

This is particularly important if you:

  • Have diabetes.
  • Have a history of eating disorders.
  • Are a woman who is trying to conceive.
  • Are a woman with a history of amenorrhea.
  • Are pregnant or breastfeeding.

All that being said, intermittent fasting has an outstanding safety profile. There is nothing dangerous about not eating for a while if youre healthy and well-nourished overall.


The most common side effect of intermittent fasting is hunger. People with certain medical conditions should not fast without consulting with a doctor first.

Here are answers to the most common questions about intermittent fasting.

Side Effects And Risks

In general, intermittent fasting is safe to try if you are relatively healthy, says Contreras. That’s because you’re still getting all the nutrients and calories that your body needs, just compressing your consumption into fewer hours of the day.;

However, intermittent fasting has been linked to muscle loss. In addition, certain people should proceed with caution when it comes to intermittent fasting since they have more nuanced nutritional needs. Contreras says you should speak with your doctor before starting if you are:;

  • Under age 18
  • Have struggled with eating disorders in the past
  • Are over 65
  • Have type 2 diabetes

In fact, that’s a good idea for anyone who has never done intermittent fasting, since a doctor who is familiar with this approach can help you make sure you’re still getting all the nutrients needed to stay healthy.;

That doesn’t mean starting intermittent fasting will be easy, especially at the beginning. Contreras says you may experience the following symptoms when you start fasting:;

  • Hunger;
  • Irritability;
  • Headaches;

While these typically aren’t risks to your health, you should contact a doctor or call 911 immediately if you experience lightheadedness, dizziness, or changes to your alertness.;

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Benefits Of Intermittent Fasting For Women Over 50

  • Benefits of Intermittent Fasting for Women Over 50

Intermittent fasting for women over 50 could help with weight loss and minimizing the chance of developing typically age-related illnesses. In fact, intermittent fasting can lower blood pressure, according to a new study done by Baylor College of Medicine. The study showed that fasting lowers blood pressure by reshaping the gut microbiota.

Of course, in addition to wanting to improve their health, losing weight is a major concern for many women over 50. A few things that make it tougher to lose weight after age 50 include lower metabolism, achy joints, reduced muscle mass, and even sleep issues. At the same time, losing fat, especially dangerous belly fat, can dramatically reduce your risk for such serious health issues as diabetes, heart attacks, and cancer.

Of course, as you age, the risk of developing many diseases increases. In some cases, intermittent fasting for women over 50 could serve as a virtual fountain of youth when it comes to weight loss and minimizing the chance of developing typically age-related illnesses.

Intermittent Fasting May Make You Feel Sick

A Rookie

Depending on the length of the fasting period, people may experience headaches, lethargy, crankiness, and constipation. To decrease some of these unwanted side effects, you may want to switch from adf fasting to periodic fasting or a time restricted eating plan that allows you to eat everyday within a certain time period.

Also Check: Does Fasting Help With Belly Fat

Intermittent Fasting Can Be Hard But Maybe It Doesnt Have To Be

Initial human studies that compared fasting every other day to eating less every day showed that both worked about equally for weight loss, though people struggled with the fasting days. So, I had written off IF as no better or worse than simply eating less, only far more uncomfortable. My advice was to just stick with the sensible,;,;;diet.

New research is suggesting that not all IF approaches are the same, and some are actually very reasonable, effective, and sustainable, especially when combined with a nutritious plant-based diet. So Im prepared to take my lumps on this one .

We have evolved to be in sync with the day/night cycle, i.e., a circadian rhythm. Our metabolism has adapted to daytime food, nighttime sleep. Nighttime eating is well associated with a higher risk of obesity, as well as;.

Based on this, researchers from the University of Alabama conducted;a study;with a small group of obese men with prediabetes. They compared a form of intermittent fasting called “early time-restricted feeding,” where all meals were fit into an early eight-hour period of the day ,or spread out over 12 hours . Both groups maintained their weight but after five weeks, the eight-hours group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure. The best part? The eight-hours group also had significantly decreased appetite. They werent starving.

Isnt It Important To Have Breakfast Every Morning

Not necessarily. This appears to be an old misconception, based on speculation and statistics, and it does not hold up when its tested.57 Skipping your morning meal gives your body more time to burn fat for energy. Since hunger is lowest in the morning, it may be easiest to skip it and break your fast later in the day.58

Learn more:

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Fasting For Everyone Not So Much

There are caveats to fasting.

First and most importantly, not everyone should do it.

People prone to dysglycemia or irregular blood sugar levels will struggle with fasting. Similarly, Type 1 and 2 diabetics absolutely need to be closely monitored by a professional to avoid life-threatening complications like hypoglycemia.

For those with moderate to severe inflammatory bowel disease, this isnt for you either. Not now anyway.

People with a history of an eating disorder should not attempt intermittent fasting.

What About my Adrenals?!

Other exceptions include those with hypothalamic-pituitary-adrenal-thyroid problems. Whats this you ask??

This can manifest as the following symptoms:

  • Low energy/burnout
  • Frequent infections and immune challenges
  • Significant hair thinning, falling out or very dry skin
  • Cold intolerance
  • Insomnia
  • Weight gain

Why? because intermittent fasting works because it stresses your body into adaptation. If youre already under a tremendous amount of stress then theres no more room for adaptation! This can cause the symptoms mentioned above. It can generally cause people to feel lousy and defeated because they didnt respond like everyone else. If this applies to you then it may be necessary to support those systems first before considering intermittent fasting or it might make them worse.

If you do decide to give fasting a try you need to watch out for these potential side effects.

Drawbacks Of 16/8 Intermittent Fasting

Dr.Berg’s Webinar on Healthy Ketosis & Intermittent Fasting Plan

16/8 intermittent fasting may be associated with many health benefits, but it does come with some drawbacks and may not be right for everyone.

Restricting your intake to just eight hours per day can cause some people to eat more than usual during eating periods in an attempt to make up for hours spent fasting.

This may lead to weight gain, digestive problems and the development of unhealthy eating habits.

16/8 intermittent fasting may also cause short-term negative side effects when youre first getting started, such as hunger, weakness and fatigue though these often subside once you get into a routine.

Additionally, some research suggests that intermittent fasting may affect men and women differently, with animal studies reporting that it could interfere with fertility and reproduction in females .

However, more human studies are needed to evaluate the effects that intermittent fasting may have on reproductive health.

In any case, be sure to start gradually and consider stopping or consulting your doctor if you have any concerns or experience negative symptoms.


Restricting daily food intake may cause weakness, hunger, increased food consumption and weight gain. Animal studies show that intermittent fasting may impact men and women differently and may even interfere with fertility.

Also Check: What Can You Eat Or Drink During Intermittent Fasting

Example Daily Food Plan: 16/8 Method

7:00AM: Wake up and have coffee without creamer or sugar.; Better yet drink a tall glass of water.; Even black coffee does have the ability to spike insulin in some people.;;

11:00AM: Begin 8 hours of eating. Have some paleo pancakes ; and grass grazed butter; .

3:00PM: Snack of carrots and hummus or a cup of nuts

6:00PM: Low carb pasta and sugar-free Paleo pasta sauce of your choosing ;

7:00PM: Make sure that you are done eating by this time. Your 8 hours are over; try drinking some sleepy time tea or more water to wind down for the night.;

May Play A Role In Cancer Treatment And Prevention

This potential benefit is still a bit up in the air. Animal models have shown that periodic fasting may help protect normal cells from the toxic effects of chemotherapy drugs while sensitizing cancer cells to the treatment .;

When it comes to human trials, the data is still inconclusive. Weight control and reduced inflammation in the body could reduce the development of cancer, but further research is needed to understand the role fasting may play in cancer treatment .;;

Recommended Reading: Do’s And Don Ts Of Intermittent Fasting

Can I Exercise During Fasting

Yes. You can continue all your usual activities, including exercise, while fasting.37 You do not need to eat before exercising to provide energy.38 Instead, your body can burn stored energy for fuel.

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

What Happens To Your Body When You Fast

Incredible Benefits Of Intermittent Fasting You Should Know

Fasting is a way to give your body a break. Heres how intermittent fasting works for weight loss.

Stage 1: In between 0 to 4 hours, your blood sugar remains high. Your body is using up the energy in this phase.

Stage 2:; 4 to 16 hours, your body now starts releasing fats and uses them to release ketone bodies and chemicals.;

Stage 3: 16 to 24 hours, after an overnight fast, you are almost low on glycogen level. Your energy demands at this stage havent changed much but now the chemicals start to break into AMP-activated protein. They help in cell growth and regulating energy response to your starvation period.

Stage 4: 24 to 72 hours, now your body will start breaking down your muscles to utilize protein for energy. This means it enters the state of ketosis which acts as fuel for your brain and body.

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May Help Prevent Alzheimers Disease

Alzheimers disease is the worlds most common neurodegenerative disease.

Theres no cure currently available for Alzheimers, so preventing it from showing up in the first place is critical.

Studies in rats and mice show that intermittent fasting may delay the onset of Alzheimers or reduce its severity 00503-2″ rel=”nofollow”>29, 36, 37 ).

In a series of case reports, a lifestyle intervention that included daily short-term fasts was able to significantly improve Alzheimers symptoms in 9 out of 10 people .

Animal studies also suggest that fasting may protect against other neurodegenerative diseases, including Parkinsons disease and Huntingtons disease 00503-2″ rel=”nofollow”>29, 39, 40).

However, more research in humans is needed.


Studies in animals suggest that intermittent fasting may be protective against neurodegenerative diseases such as Alzheimers disease.

The Dangers Of Intermittent Fasting

Intermittent fasting is a predetermined period where an individual purposely doesnt eat food. From a 12-hour fast to alternate day fasting, many kinds of intermittent fasting diets are becoming increasingly popular. Health professionals;argue that intermittent fasting is not necessarily dangerous, but many also agree that intermittent fasting is not safe for everyone.

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What Is Intermittent Fasting

Many diets focus on what to eat, but intermittent fasting is all about when you eat.

With intermittent fasting, you only eat during a specific time. Fasting for a certain number of hours each day or eating just one meal a couple days a week, can help your body burn fat. And scientific evidence points to some health benefits, as well.

Johns Hopkins neuroscientist , has studied intermittent fasting for 25 years. He says that our bodies have evolved to be able to go without food for many hours, or even several days or longer. In prehistoric times, before humans learned to farm, they were hunters and gatherers who evolved to survive and thrive for long periods without eating. They had to: It took a lot of time and energy to hunt game and gather nuts and berries.

Even 50 years ago, it was easier to maintain a healthy weight. Johns Hopkins dietitian Christie Williams, M.S., R.D.N., explains: There were no computers, and TV shows turned off at 11 p.m.; people stopped eating because they went to bed. Portions were much smaller. More people worked and played outside and, in general, got more exercise.

Nowadays, TV, the internet and other entertainment are available 24/7. We stay awake for longer hours to catch our favorite shows, play games and chat online. Were sitting and snacking all day and most of the night.

Examples Of Different Intermittent Fasting Schedules

Is Intermittent Fasting Healthy?

If youre considering giving fasting a shot, there are a few different options for working it into your lifestyle.

Daily Intermittent Fasting

Most of the time, I follow the Leangains model of intermittent fasting, which uses a 16hour fast followed by an 8hour eating period. This model of daily intermittent fasting was popularized by Martin Berkhan of, which is where the name originated.

It doesn’t matter when you start your 8hour eating period. You can start at 8am and stop at 4pm. Or you start at 2pm and stop at 10pm. Do whatever works for you. I tend to find that eating around 1pm and 8pm works well because those times allow me to eat lunch and dinner with friends and family. Breakfast is typically a meal that I eat on my own, so skipping it isn’t a big deal.

Because daily intermittent fasting is done every day it becomes very easy to get into the habit of eating on this schedule. Right now, you’re probably eating around the same time every day without thinking about it. Well, with daily intermittent fasting it’s the same thing, you just learn to not eat at certain times, which is remarkably easy.

Weekly Intermittent Fasting

One of the best ways to get started with intermittent fasting is to do it once per week or once per month. The occasional fast has been shown to lead to many of the benefits of fasting we’ve already talked about, so even if you don’t use it to cut down on calories consistently there are still many other health benefits of fasting.

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The Physiology Of Intermittent Fasting

If all the perks of time-restricted eating sound almost too good to be true, a further exploration of the physiological mechanisms behind IF, namely ketosis and autophagy, will help illustrate how this dietary approach can yield such a plethora of covetable wellness benefits.

KetosisKetosis is a natural metabolic state in which the body produces ketone bodies out of fat that are used as the bodyâs energy source, instead of carbohydrates. Glucose from carbohydrates is the preferred fuel source for most cells in the body; however, by following a high-fat, very low carbohydrate âketogenic dietâ or through fasting, you can force your body to switch over into ketosis. Experts generally suggest you need to fast for a minimum of 12 hours in order to transition into this ketogenic metabolic state where you begin calling on ketone bodies in conjunction with free fatty acids as the bodyâs primary fuel.

The presence of ketones may help to prevent the development of many chronic diseases through reducing oxidative stress and inflammation. In addition, research has shown that being in ketosis can regulate appetite, normalise blood sugar and insulin response and support weight loss.

Practising IF as an eating pattern that includes regular, short-term fasts has become a popular lifestyle choice, propelled by the potential benefits such as weight loss, improved body composition, disease prevention, longevity and overall wellbeing.


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