Typically, intermittent fasting permits nothing but water, tea, or coffee for the entire hour fasting period. But hey, it's not as if Aniston's having soda for breakfast. And she's not the only one to extol the virtues of celery juice—it seems like every other social media influencer celebrates the green stuff as well.

Any magical health benefits of celery juice are exaggerated "beyond the fact [that] it's a vegetable," said Harris-Pincus. Yet if it works for you, go for it. The diet isn't suitable for everyone. Freirich doesn't advise it for people with diabetes or problems with low blood pressure or low blood sugar, athletes, or pregnant individuals.

Intermittent fasting shouldn't come with any nasty side effects, but—like all restrictive eating plans—it's important to not let it take over your life. It's also important to pay attention to exercise in relation to fasting. Harris-Pincus warned against exercising while fasting or waiting several hours after exercising to eat your first meal.

There are some benefits from intermittent fasting, but ultimately, how and when you eat is up to you. If you are trying to lose weight, you have to remain in a calorie deficit regardless of when you consume those calories.

If you are debating intermittent fasting, but aren't sure if it's right for you, reach out to a registered dietitian or healthcare provider. Use limited data to select advertising. Create profiles for personalised advertising. Use profiles to select personalised advertising.

Create profiles to personalise content. Use profiles to select personalised content. Measure advertising performance. Measure content performance. Understand audiences through statistics or combinations of data from different sources.

Develop and improve services. Some studies have shown beneficial effects of IF on physical activity performance, including studies done on elite cyclists, generally healthy active women and men. However, one small study showed a negative impact on sprinting performance in males.

Some studies concluded that IF may improve memory and brain health. Other research has shown that IF may result in improved metabolism. Additional, larger clinical trials and research is needed to determine whether IF is beneficial in other ways and in the long term.

Metabolism is a term that refers to all of the chemical processes or changes that occur in the body at the cellular level. These changes make energy and the materials organisms and cells need in order to grow, reproduce, and maintain life.

In relation to diet, metabolism is the process of digesting or breaking down the food you eat into a simpler form the body is able to use. Metabolism is also involved when your body breaks down muscle or stored fat to be used as energy during periods of strenuous exercise or fasting.

Always talk with a healthcare provider before starting a new diet or eating pattern, especially if you have a known medical condition. IF may be unsafe for people with diabetes who take insulin or other glucose-lowering medications and people who are on medication that needs to be taken with food.

Individuals with a history of disordered eating, children under 18, and people who are pregnant or breastfeeding should not follow IF diets. A review of human trials found that fasting may reduce levels of androgens reproductive and growth hormones , which can negatively impact metabolic health and libido sexual desire in males.

Some studies suggest that women may be more sensitive to fasting, most likely relating to fluctuating hormones. One small study concluded that IF may increase stress in women,.

Intermittent fasting IF involves periods of fasting alternating with periods of eating. There are several methods of IF with variations in the amount of time spent fasting versus eating. Fasting for health is done for different reasons, including weight loss, disease prevention or management, and to help improve other aspects of health, such as physical performance, metabolism, and brain health.

People with diabetes who take insulin or other glucose-lowering medications and those who are on medication that needs to be taken with food should not follow IF eating patterns.

Others who should also avoid IF include individuals with a history of disordered eating, children under 18, and pregnant or breastfeeding people. Talk with a healthcare provider if you are considering trying IF. Chair SY, Cai H, Cao X, Qin Y, Cheng HY, Ng MT.

Intermittent fasting in weight loss and cardiometabolic risk reduction: a randomized controlled trial. J Nurs Res. Seimon RV, Roekenes JA, Zibellini J, et al.

Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Mol Cell Endocrinol. Guo Y, Luo S, Ye Y, Yin S, Fan J, Xia M.

Intermittent fasting improves cardiometabolic risk factors and alters gut microbiota in metabolic syndrome patients. J Clin Endocrinol Metab. Moro T, Tinsley G, Longo G, et al. Time-restricted eating effects on performance, immune function, and body composition in elite cyclists: a randomized controlled trial.

J Int Soc Sports Nutr. Martínez-Rodríguez A, Rubio-Arias JA, García-De Frutos JM, Vicente-Martínez M, Gunnarsson TP. Effect of high-Intensity Interval training and Intermittent fasting on body composition and physical performance in active women.

Int J Environ Res Public Health. Moro T, Tinsley G, Bianco A, et al. J Transl Med. Cherif A, Meeusen R, Farooq A, et al. Three days of intermittent fasting: repeated-sprint performance decreased by vertical-stiffness impairment.

Int J Sports Physiol Perform. Seidler K, Barrow M. Intermittent fasting and cognitive performance - Targeting BDNF as potential strategy to optimise brain health.

However, it is best to use caution when beginning or following the eating routine. Before embarking on intermittent fasting or making any other drastic changes to your diet, consult a trusted healthcare professional to help you get started safely.

Intermittent fasting is an eating pattern during which you refrain from consuming any calories for an extended period of time. Usually, this period lasts between 12 and 40 hours 1.

Water, coffee, and other calorie-free beverages are allowed during the fast, but no solid foods or calorie-containing drinks are permitted. For example, if you finish dinner at 7 p. Some people choose to fast from breakfast to breakfast or lunch to lunch.

But which time frame works best depends on the individual. Intermittent fasting is a dietary routine that regularly alternates between periods of eating and fasting.

There are many different methods of doing so, with many requiring you to fast for 12—40 hours at a time. Researchers have already linked numerous health benefits with intermittent fasting and continue to examine them. Plus, for some people, intermittent fasting fits well into their model of a healthy and sustainable long-term diet.

Two main reasons why people try intermittent fasting are to manage their weight and metabolic health. Metabolic health is a marker of how well the body processes, or metabolizes, energy. Fasting or abstaining from food can create a calorie deficit, meaning that your body has fewer calories than it needs to maintain its current weight.

Research shows that some types of intermittent fasting can be as effective for weight loss — though not necessarily more effective — as other diets that also rely on limiting your daily calorie intake 6 , 7 , 8 , 9. Alternate-day fasting and the diet may also be effective 10 , 11 , 12 , Besides naturally eliminating your calorie intake during the fasting period, intermittent fasting may support weight loss by regulating your appetite to increase feelings of fullness while suppressing feelings of hunger 14 , 15 , Intermittent fasting might sound complicated and intimidating, but it can be simple at times.

In fact, you might even find that fasting helps simplify your day since you need to plan fewer meals. For example, having an early dinner followed by a late breakfast the next day is one way to fast intermittently. If you finish your last meal at 8 p. However, other people instinctively eat this way already.

They may be more prone to trying out an intermittent fasting eating pattern. For example, intermittent fasting might work particularly well for someone who wants to pair it with a resistance training program and a high protein diet Intermittent fasting is often used to manage weight and metabolic health.

The eating routine might help lower blood pressure, blood sugar, and blood fat levels. For some people, it also works as part of a healthy long-term diet pattern.

Intermittent fasting is one way to regulate your calorie intake and work toward improving your metabolic health. Though the eating pattern can certainly be part of a healthy diet, it will likely take some adjusting to in the beginning. Plus, simply put, intermittent fasting is not right for everyone.

For some people, using those tactics to keep your calorie intake within a designated time frame is no problem, but for others, it might feel unnatural at first. Further, if you prefer not to follow a strict schedule, you might find intermittent fasting frustrating. You may go to bed hungry several times per week.

That may naturally feel unpleasant and unsustainable in the long term Plus, at times, it might be necessary to override your natural hunger and fullness cues in order to not break your fast earlier than planned.

Freirich, MS, RD, CDN , New York-based nutritionist and registered dietitian, told Health. Other types of intermittent fasting diets include the diet, which involves fasting for two nonconsecutive days each week and eating without restrictions on the other five days.

There's also the OMAD—or one meal a day—diet. Intermittent fasting is rather popular, and it's easy to see why. For starters, there's no prescribed calorie limit, which means no crunching numbers and relying on calorie counting guides before eating.

But what else is involved in the eating plan and similar fasts, and are they actually safe? Here's what nutrition experts have to say. As far as the benefits of intermittent fasting go, one study published in Nutrition and Healthy Aging in June found that this fast helped people lose a "modest" amount of weight and also lowered their blood pressure.

Some advocates of the diet assert it helps control blood sugar levels and boost brain function, but there's little scientific evidence to back these claims up. And if you don't stick to nutritious food during the eight-hour window, any positive effects are quickly negated.

In other words, 16 hours of fasting doesn't compensate for eight hours of eating junk food. For the best results, you should be careful about your choice of eating window.

According to Freirich, it should start early in the day, preferably no later than about 10 a. If you choose a much later eating window, say 4 p.

to 12 a. Aniston also told Radio Times that she likes to start her day with celery juice around 9 a. Typically, intermittent fasting permits nothing but water, tea, or coffee for the entire hour fasting period.

But hey, it's not as if Aniston's having soda for breakfast. And she's not the only one to extol the virtues of celery juice—it seems like every other social media influencer celebrates the green stuff as well. Any magical health benefits of celery juice are exaggerated "beyond the fact [that] it's a vegetable," said Harris-Pincus.

Yet if it works for you, go for it. The diet isn't suitable for everyone. Intermittent fasting is not a diet plan. You then eat during another period of time each day usually a smaller period of time. How fasting and eating is divided each day is called an eating schedule. One of the most common, easy-to-follow schedules is This means you fast for a 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. until 11 a. the next day. You would then eat a healthy lunch and dinner between 11 a.

and 7 p. This is just an example of times. You can select any hour and 8-hour block of time that works best for your schedule. Other intermittent fasting schedules include when you fast for 18 hours and eat for 6 hours or alternating days. With alternating days, you fast for 24 hours, then eat a healthy diet for the next 24 hours, then fast again for the following 24 hours.

This schedule continues using the every-other-day format. Another schedule option is This is when you fast for two days a week, and eat a normal, healthy diet the other five days. This is a little different, though, as this schedule allows you eat one small meal of to calories on your fasting days.

During your eating window, focus on eating a healthy diet and maintaining portion control. Some people choose to use the Mediterranean diet as a guideline for what to eat.

This plan focuses on fruits, vegetables, beans, whole grains, and fish. You can also choose lean proteins and healthy fats. Fasting for at least 12 hours changes how your metabolic system works. Your metabolic system is how your body changes the foods and beverages you consume into energy.

Most of the time, your body gets its energy from a sugar called glucose. Glucose is found in the foods you eat and beverages you drink. When this happens, the fatty acids in your body are absorbed into your blood. They produce a chemical called ketones.

Your body then uses the ketones as its energy source. This is called a metabolic switch. Your body is switching from glucose to ketones.

When your body uses ketones instead of fat, you may lose weight. They should also include some carbohydrates. Although it is possible to eat some foods during the fasting period, it can be challenging to stick to strict guidelines on when and what to eat in the long term.

Also, some people have trouble eating such a large meal so close to bedtime. There is also a risk that people on this diet will not eat enough nutrients, such as fiber.

This can increase the risk of cancer and have an adverse effect on digestive and immune health. The following tips may help people stay on track and maximize the benefits of intermittent fasting:.

People who are starting intermittent fasting for the first time may find the 12 hour fasting method the easiest. This involves fasting for 12 hours every hours period. People can include time when they are asleep in this fasting window, for example, fasting from 7 p.

The amount of weight someone can lose with intermittent fasting depends on various factors, including the type and duration of fasting, their current weight, and how many calories they consume when they are not fasting. The effectiveness of different fasting methods may vary between people.

Fasting for 16 hours may be effective for people who did not see results when fasting for 12 hours. Some fasting practices may involve fasting for one day a week, every other day, or two days a week. People should speak with a healthcare professional to ensure they are staying safe when fasting.

There are many ways to do intermittent fasting, and there is no single plan that will work for everyone. Individuals will experience the best results if they try out the various styles to see what suits their lifestyles and preferences.

Regardless of the type of intermittent fasting, fasting for extended periods when the body is unprepared can be problematic. These forms of dieting may not be suitable for everyone. If a person is prone to disordered eating, these approaches may exacerbate their unhealthy relationship with food.

People with health conditions, including diabetes, should speak with a doctor before attempting any form of fasting. For the best results, it is essential to eat a healthful and balanced diet on non-fasting days. If necessary, a person can seek professional help to personalize an intermittent fasting plan and avoid pitfalls.

People should reach out to a registered dietitian to help them choose the best intermediate fasting that fits their lifestyle. Read the article in Spanish. Intermittent fasting is a diet plan that means consuming few to no calories on fasting day and eating normally on nonfasting days.

We look at the…. Intermittent fasting has many potential benefits. Tips to start include having a goal and choosing a suitable method. A new clinical trial shows that time-restricted eating, also known as intermittent fasting, helps relieve symptoms of metabolic syndrome. Take a break from COVID news and explore these fascinating stories on other topics.

My podcast changed me Can 'biological race' explain disparities in health? Why Parkinson's research is zooming in on the gut Tools General Health Drugs A-Z Health Hubs Health Tools Find a Doctor BMI Calculators and Charts Blood Pressure Chart: Ranges and Guide Breast Cancer: Self-Examination Guide Sleep Calculator Quizzes RA Myths vs Facts Type 2 Diabetes: Managing Blood Sugar Ankylosing Spondylitis Pain: Fact or Fiction Connect About Medical News Today Who We Are Our Editorial Process Content Integrity Conscious Language Newsletters Sign Up Follow Us.

Medical News Today. Health Conditions Health Products Discover Tools Connect. Six ways to do intermittent fasting. Medically reviewed by Marie Lorraine Johnson MS, RD, CPT — By Jayne Leonard — Updated on November 13, Intermittent fasting methods Tips for fasting FAQ Outlook.

A note about sex and gender Sex and gender exist on spectrums.