Intermittent fasting is a dietary trend that includes blocks of time when you eat normally and blocks of time when you don’t eat anything.
Types of intermittent fasting include when you only eat for a certain number of hours each day or when you eat small amounts of food for a few days a week and eat normally on other days.
Most people can try intermittent fasting, but it is not recommended for children, adolescents, people with an eating disorder, if you are pregnant or breastfeeding or if you have certain medical conditions.
While intermittent fasting can lead to weight loss, more research about other health benefits is needed.
It’s important to speak to your doctor before you start intermittent fasting, as your doctor will assess your general health and advise if it is a good option for you.
What is intermittent fasting?
Intermittent fasting is a dietary trend which involves you eating normally at specific times, while at other times you have low or no food intake. With intermittent fasting, there are no foods you should or shouldn’t eat, just rules around the timing or amount of eating. Intermittent fasting is also known as intermittent energy restriction.
How does intermittent fasting work?
When you are intermittent fasting, you have times where you don’t eat anything, which means that you are eating less food in a day or a week overall. During the times that you are eating, you should eat normally, with a focus on nutritious foods. You can drink water at any time, including when you are fasting.
Research into the other ways that intermittent fasting works, such as if it affects how your body processes energy while you are fasting, is being done. There are no conclusive results released on this yet.
What are examples of intermittent fasting?
There are many different ways you can do intermittent fasting. Different types include:
time restricted eating, such as the 16:8 plan when you eat for an 8-hour window in a day and then fast for the remaining 16 hours of the day
5:2 diet, when you choose 2 days each week to have only a small amount of food, usually between 2000 and 3000 kilojoules, but eat normally the other 5 days
eat-stop-eat when you fast for 24 hours 1 or 2 days a week
Is intermittent fasting safe?
Intermittent fasting can be safe for some people, but it is not suitable for everyone.
Usually, you will feel hungry when you first start intermittent fasting and you may also experience headaches. Your body should become used to the intermittent fasting.
If you are feeling weak, anxious, irritable, unable to concentrate or unable to do you usual activities, stop intermittent fasting and speak to your doctor.
You may need to increase how much water you drink to make sure you don’t become dehydrated, as your body relies not only on water but also fluid from the food that you normally eat to keep hydrated.
If you fall into any of these groups you should not do intermittent fasting:
If you are having treatment for cancer or taking diabetes medicines, you should speak to your doctor to see if intermittent fasting is safe for you.
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Are there any health benefits of intermittent fasting?
Most of the original research on intermittent fasting was done on animals, and many of the benefits that people claim have not been confirmed in humans. While more research is needed on the benefits of intermittent fasting, it seems that having regular meals and avoiding late night food or lots of snacks is good for your health.
Some research has shown that the benefits of intermittent fasting on your health and weight are due to eating fewer calories and that the timing of when you eat doesn’t make a difference.
Recent research in humans has found that while you may lose weight with intermittent fasting, you don’t get the same health benefits as other diets that reduce calories while still making sure that you get the nutrients you need. This may be because you are not getting enough of the right nutrients in your diet with intermittent fasting.
Other research has shown that only eating at certain times of the day can help with how your body processes sugar and your blood pressure, even if you are not eating less calories.
When should I see a doctor?
If you are considering intermittent fasting, you should see your doctor before you start, to make sure it’s right for you. They also may need to adjust your medicine doses if you have any.
If you are intermittent fasting, a dietitian can advise you about what foods you should eat to make sure that you are still getting all the nutrients you need.
To find a dietitian near you, use the healthdirect Service Finder tool.
FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.
The Research So Far. A systematic review of 40 studies found that intermittent fasting was effective for weight loss, with a typical loss of 7-11 pounds over 10 weeks. [2] There was much variability in the studies, ranging in size from 4 to 334 subjects, and followed from 2 to 104 weeks.
Fung says the most common fasting strategy is 16 hours of fasting and eating within an eight-hour time period. "So you might eat for example from 11 a.m. to 7 p.m. or you might do it early, say 9 a.m. until 4 p.m. There's various ways to do it, but that's one of the more popular schedules," he said.
If you consistently stay active while following intermittent fasting, you can lose as much as 6-8 pounds per month. This estimation is shockingly high when you consider that all you have to do is not eat for select hours throughout the day.
Intermittent fasting has been shown to improve insulin sensitivity, reduce blood sugar levels, and lower the risk of developing type 2 diabetes. In addition, after one month of intermittent fasting, you may notice improved metabolic health and reduced risk of chronic diseases.
While both 12-hour and 16-hour fasting can promote fat burning, it's possible that a 16-hour fast may be more effective. This is because the longer fasting period may lead to a greater depletion of glycogen stores, which can trigger higher levels of fat burning.
For example, studies have found that people who regularly fast more than 16 or 18 hours a day have a higher risk of gallstones. They're also more likely to need surgery to remove the gallbladder. Eating for 12 hours and then fasting for 12 hours is likely safe for most people, Longo explains.
Intermittent fasting is safe for many people, but it's not for everyone. Skipping meals may not be the best way to manage your weight if you're pregnant or breast-feeding. If you have kidney stones, gastroesophageal reflux, diabetes or other medical problems, talk with your doctor before starting intermittent fasting.
Restricting calories can cause intense hunger. You may become preoccupied with food, leading to overeating and weight gain. For example, when you don't eat for a long time, your body releases large amounts of the hormone ghrelin, which influences hunger.
A 2023 review of research found that the 16/8 method and 16/8 combined with restricting calories were effective strategies for weight control in adults with overweight or obesity. An eating window starting before noon led to greater weight loss than one that began after noon.
How much, though, depends on what kind of intermittent fasting schedule you're following (more on those schedules, below). People who do some form of full-day fasts usually lose about 10 to 30 pounds over a three-to-six-month period, says Varady.
Going too long without eating might actually encourage your body to start storing more fat in response to starvation. Mattson's research shows that it can take two to four weeks before the body becomes accustomed to intermittent fasting. You might feel hungry or cranky while you're getting used to the new routine.
It's not a diet, so unless you have individual dietary restrictions, you can eat whatever you want within the eight-hour time frame. But the plan will work best for weight loss if you are already making smart, nutrient-rich choices, said NBC News health and nutrition editor Madelyn Fernstrom, Ph. D.
Many people begin to see some results within the first few weeks of starting intermittent fasting. This can include weight loss, increased energy, and improved mental clarity. However, it's important to note that sustainable, long-term health and body composition changes can take several months or even longer.
That's how long it takes your body to switch from using glucose for energy to using fat for energy. Additionally, it will take your body a while to get used to this new eating schedule. So don't expect results right away. You may need to wait between 2 and 4 weeks to see or feel any results.
Fasting on either a daily or weekly basis helps your body burn fat. There are different approaches to intermittent fasting but the most popular include: Alternate day fasting includes normal eating every other day, with days of restricted eating (500 calories) in between.
For weight loss and improved metabolic health, it could take a month. If your goal is to increase longevity and overall health, you'll likely need to incorporate intermittent fasting consistently for the long term. It's important to note that intermittent fasting results also depend on your overall diet.
To get the benefits of intermittent fasting, you need to fast for at least 12 hours. That's how long it takes your body to switch from using glucose for energy to using fat for energy.
Many people begin to see some results within the first few weeks of starting intermittent fasting. This can include weight loss, increased energy, and improved mental clarity. However, it's important to note that sustainable, long-term health and body composition changes can take several months or even longer.
If you've tried intermittent fasting but aren't losing weight, possible reasons why include overeating during your eating window and poor food choices. To help, you can try eating fewer calories, work on balancing your meals, or create a smaller or larger eating window.
Introduction: My name is Terence Hammes MD, I am a inexpensive, energetic, jolly, faithful, cheerful, proud, rich person who loves writing and wants to share my knowledge and understanding with you.
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