Intermittent fasting involves periods of entirely or partially abstaining from eating. There are many methods of intermittent fasting that vary in the number of fast days and the calorie allowances.

Some studies suggest that this way of eating may offer benefits such as fat loss, better health, and increased longevity. Proponents claim that an intermittent fasting program is easier to maintain than traditional, calorie-controlled diets.

An intermittent fasting pattern is based on a set schedule and does not follow random times. That said, each person’s experience of intermittent fasting is individual, and different styles will suit different people.

In this article, we discuss the research behind the most popular types of intermittent fasting and provide tips on maintaining this type of diet.

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There are various methods of intermittent fasting, and people will prefer different styles. Read on to find out about six different ways to do intermittent fasting.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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1. Fast for 12 hours a day

The rules for this diet are simple. A person needs to decide on and adhere to a 12-hour fasting window every day.

According to some researchers, fasting for 10–16 hours can cause the body to turn its fat stores into energy, which releases ketones into the bloodstream. This should encourage weight loss.

This type of intermittent fasting plan may be a good option for beginners. This is because the fasting window is relatively small, much of the fasting occurs during sleep, and the person can consume the same number of calories each day.

The easiest way to do the 12-hour fast is to include the period of sleep in the fasting window.

For example, a person could choose to fast between 7 p.m. and 7 a.m. They would need to finish their dinner before 7 p.m. and wait until 7 a.m. to eat breakfast but would be asleep for much of the time in between.

2. Fasting for 16 hours

Fasting for 16 hours a day, leaving an eating window of 8 hours, is called the 16:8 method or the Leangains diet.

During the 16:8 diet, males fast for 16 hours each day, and females fast for 14 hours. This type of intermittent fast may be helpful for someone who has already tried the 12-hour fast but did not see any benefits.

On this fast, people usually finish their evening meal by 8 p.m. and then skip breakfast the next day, not eating again until noon.

A study on mice on a high fat diet found that limiting the feeding window to 8 hours protected them from obesity, inflammation, diabetes, and liver disease, even when they ate the same total number of calories as mice that ate whenever they wished.

3. Fasting for 2 days a week

People following the 5:2 diet eat standard amounts of healthful food for 5 days and reduce calorie intake on the other 2 days.

During the 2 fasting days, males generally consume 600 calories and females 500 calories.

Typically, people separate their fasting days in the week. For example, they may fast on a Monday and Thursday and eat regularly on the other days. There should be at least 1 non-fasting day between fasting days.

There is limited research on the 5:2 diet, which is also known as the Fast diet. A study involving 107 overweight or obese women found that restricting calories twice weekly and continuous calorie restriction both led to similar weight loss.

The study also found that this diet reduced insulin levels and improved insulin sensitivity among participants.

A small-scale study looked at the effects of this fasting style in 23 overweight women. Over the course of one menstrual cycle, the women lost 4.8% of their body weight and 8.0% of their total body fat. However, these measurements returned to usual for most of the women after 5 days of typical eating.

4. Alternate day fasting

There are several variations of the alternate day fasting plan, which involves fasting every other day.

For some people, alternate day fasting means a complete avoidance of solid foods on fasting days, while other people allow up to 500 calories. On feeding days, people often choose to eat as much as they want.

One study reports that alternate day fasting is effective for weight loss and heart health in healthy and overweight adults. The researchers found that the 32 participants lost an average of 5.2 kilograms (kg), or just over 11 pounds (lb), over a 12-week period.

Alternate day fasting is an extreme form of intermittent fasting, and it may not be suitable for beginners or those with certain medical conditions. It may also be difficult to maintain this type of fasting in the long term.

5. A weekly 24-hour fast

Fasting completely for 1 or 2 days a week, known as the Eat-Stop-Eat diet, involves eating no food for 24 hours at a time. Many people fast from breakfast to breakfast or lunch to lunch.

People on this diet plan can have water, tea, and other calorie-free drinks during the fasting period.

People should return to regular eating patterns on non-fasting days. Eating in this manner reduces a person’s total calorie intake but does not limit the specific foods the individual consumes.

A 24-hour fast can be challenging, and it may cause fatigue, headaches, or irritability. Many people find these effects become less extreme over time as the body adjusts to this new eating pattern.

People may benefit from trying a 12-hour or 16-hour fast before transitioning to the 24-hour fast.

6. The Warrior Diet

The Warrior Diet is a relatively extreme form of intermittent fasting.

The Warrior Diet involves eating very little, usually just a few servings of raw fruit and vegetables, during a 20-hour fasting window, then eating one large meal at night. The eating window is usually only around 4 hours.

This form of fasting may be best for people who have tried other forms of intermittent fasting already.

Supporters of the Warrior Diet claim that humans are natural nocturnal eaters and that eating at night allows the body to gain nutrients in line with its circadian rhythms.

During the 4-hour eating phase, people should make sure that they consume plenty of vegetables, proteins, and healthy fats. 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.

It can be challenging to stick to an intermittent fasting program.

The following tips may help people stay on track and maximize the benefits of intermittent fasting:

  • Staying hydrated. Drink lots of water and calorie-free drinks, such as herbal teas, throughout the day. This can help ensure you get enough electrolytes, sodium, and potassium chloride.
  • Avoiding thinking about food. Plan plenty of distractions on fasting days to avoid thinking about food, such as catching up on paperwork or going to see a movie.
  • Resting and relaxing. Avoid strenuous activities on fasting days, although light exercise such as yoga may be beneficial.
  • Making every calorie count. If the chosen plan allows some calories during fasting periods, select nutrient-dense foods that are rich in protein, fiber, and healthful fats. Examples include beans, lentils, eggs, fish, nuts, avocado, and unprocessed meats.
  • Eating high-volume foods. Select filling yet low calorie foods, which include popcorn, raw vegetables, and fruits with high water content, such as grapes and melon.
  • Increasing the taste without the calories. Season meals generously with garlic, herbs, spices, or vinegar. These foods are extremely low in calories yet are full of flavor, which may help to reduce feelings of hunger.
  • Choosing nutrient-dense foods after the fasting period. Eating foods that are high in fiber, vitamins, minerals, and other nutrients helps to keep blood sugar levels steady and prevent nutrient deficiencies. A balanced diet will also contribute to weight loss and overall health.

Below are some frequently asked questions about intermittent fasting.

How does intermittent fasting work for beginners?

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 24-hours period.

People can include time when they are asleep in this fasting window, for example, fasting from 7 p.m. to 7 a.m.

How much weight can someone lose in a month with intermittent fasting?

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.

A 2023 meta-analysis states that alternate day fasting, 5:2 fasting, and time-restricted eating can cause weight loss reductions of 1–13% over 2–52 weeks.

Is it better to fast for 12 or 16 hours?

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.

How many days can someone do intermittent fasting?

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.

For more information, see MNT‘蝉 ultimate beginner’s guide to intermittent fasting.

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