Intermittent Fasting: Types and Benefits

Intermittent fasting can be a great way to lose body weight and improve your health, but it needs to be individualized to your body.

This article will discuss intermittent fasting basics, the benefits, how to do it safely, and how to make adjustments to fit your lifestyle.

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What Is Intermittent Fasting?

Intermittent fasting (IF) is an eating pattern with set periods of eating and fasting. Fasting means you completely abstain from food or drinks with calories. In the absence of nutrients, physiological adaptations kick in that can benefit your health (more on this below).¹

Intermittent fasting can include a calorie deficit, but it doesn't have to, which is why many people like it. It's more about when you eat than how much (although food quality matters too), making it less restrictive than a typical diet.

What Are the Effects of Intermittent Fasting?

Weight loss is the most popular reason for experimenting with IF. A set cutoff to stop eating helps some people reduce calorie intake from late-night, mindless snacking, and it could also naturally reduce how much you eat since the window is shorter.

But IF could support weight loss and other health benefits because of how your body responds to going longer without food. As mentioned briefly above, IF works with your body's natural physiological adaptations that happen when you aren't eating to support your metabolic health.

When your body isn't digesting and absorbing nutrients, it switches to reparative and clean-up processes. Glucose and insulin levels drop, and fatty acids become an energy source promoting weight loss and other health benefits.

We will dive into the specific health benefits linked to IF later in the article, but here are some of the foundational effects of intermittent fasting that happen in your body.²

Fasting Promotes Autophagy

Autophagy is a process where the body cleans out old, damaged cells.¹ It's a self-protective tool that reduces inflammation and oxidative stress to support cellular health.³

The metabolic pathway that turns on autophagy can only happen in the absence of nutrients (especially glucose from carbohydrates) and when insulin levels are low, so fasting is a way to turn it on.

Fasting Reduces Inflammation and Supports Healthy Immune Cells

Inflammation is a known contributor to chronic disease risk. In combination with autophagy, IF appears to reduce inflammatory markers like homocysteine, interleukin 6, and C-reactive protein (CRP), all associated with cardiovascular disease.⁴ These markers are all signals that turn on inflammation in your body, so IF could interrupt the process to lower the inflammatory burden.

Intermittent Fasting Types

IF can be adapted to fit your lifestyle. Here are the different intermittent fasting plans (note: some of these aren’t technically considered IF, but because of their popularity, we included them for reference):

The 16:8, 18:6, or 12:12 Methods

All of these types of intermittent fasting are known as time-restricted eating (TRE). They include daily periods of fasting (16 hours, 18 hours, or 12 hours) alternated with set eating windows (6 hours, 8 hours, or 12 hours).

• 16:8 method: 16:8 is the most popular type of IF because it only means pushing breakfast a few hours later than usual for many people. For example, if you follow 16:8, you'd stop eating dinner by 8 p.m. and have your first meal of the day at 12 p.m.
• 18:6 method: The 18:6 method means you'd extend your fast even more, so it's not a beginner method and is overly restrictive for many people.
• 12:12 method: Alternatively, 12:12 is a gentle, natural way of following IF for people who want the benefits but can't or don't want to follow a longer fast. It still provides a solid fasting window for reparative processes but is easier to implement. Here, you'd stop eating at 8 p.m. and have breakfast the next day at 8 a.m., which is a normal eating pattern for many.

Alternate Day Fasting and Eat-Stop-Eat

These two patterns are some of the more restrictive forms of IF and are not appropriate for everyone.

• Alternate-Day Fasting typically means fasting for 24 hours and then eating normally the following day, repeating the pattern consistently.
• Eat-Stop-Eat is similar in that it includes a full 24-hour fast, but you'd only do it once or twice a week and not on consecutive days. The other five non-fasting days, you'd eat without any restriction.

For example, someone following eat-stop-eat would fast on Monday and Thursday for the entire day but eat as usual on other days of the week.

Water Fasting

Water fasting is one of the oldest types of fasting in religious and health circles. It refers to abstaining from food or drinks except water for a set period. Intermittent fasting may be water fasting if you only drink water without tea or coffee, but when someone talks about water fasting, they are usually referring to more extended periods (and it is usually not recommended by healthcare professionals).

The 5:2 Fast

The 5:2 fast is similar to eat-stop-eat, but it allows small amounts of food (500 to 600 calories) during the two days of fasting. This method is often used in research studies, but again, it is very restrictive and not for fasting beginners.

Juice Fasts

Like water fasts, juice fasts suggest refraining from drinking or eating anything besides fruit or vegetable juice. Again, this is not the same as intermittent fasting because juices contain calories and are often high in sugar from fruit, so you wouldn’t see the benefits of autophagy, and in some cases, blood sugar could remain high (depending on the juice).

One Meal A Day (OMAD)

Just as it sounds, with OMAD, you eat one meal a day (or within a short window). While some may lose weight using this pattern, in most cases, it's just too stressful on the body and is a setup for disordered eating.

Is It a Good Idea to Intermittent Fast Every Day?

As with anything in the world of nutrition, what works for one person may not work for you. Bio-individuality means that we will all respond differently, so it's essential to understand how your body responds to fasting as you decide how to proceed.

Some people do fine with daily longer fasts, while others see better results with a gentler fast only a few days a week. Overly stressing the body can negatively impact your health, so if you notice your energy levels drop or some of the benefits you saw at the beginning start to plateau, it's time to take another look.

Key takeaway: Fasting can be modified to fit your lifestyle and should not add excess stress. If you feel starving or low energy or aren't seeing the health benefits you were looking for, it may not be the best fit for you.

What Can I Eat or Drink While Intermittent Fasting?

While fasting, you can have:

• Plain water
• Sparkling flavored water
• Unsweetened tea
• Black coffee

Since metabolic adaptations happen when your body goes without nutrients, fasting means avoiding eating or drinking anything with calories. These beverages also help you stay hydrated even when you aren't eating.

What Are Intermittent Fasting Health Benefits?

There is a lot of research on the benefits of intermittent fasting, so much so that there seems to be a new headline every day. Here are some of the top benefits of IF.

1. Fasting May Help Weight Loss Without Calorie Restriction

Some people lose weight because they eat fewer calories by limiting their eating window, but IF may support weight loss for other reasons.⁵ A study comparing weight loss interventions found that women following IF lost as much weight as those following a calorie-restricted diet.⁶

Many studies echo these results and conclude that IF is as effective if not more, than calorie restriction for weight loss.⁷ Since the body utilizes fat for fuel during fasting, IF may also be a way to target and turn on fat-burning to promote weight loss.¹

These studies are examples of why IF is so popular for weight loss, as it may feel less restrictive and easier to follow longer-term.

2. Intermittent Fasting Could Lower Diabetes Risk

IF is also used to support blood sugar and insulin levels. Research suggests that IF helps people with diabetes improve blood sugar levels without following the typical low-calorie weight loss advice.⁸

In human and animal studies, IF appears as effective (if not more effective) than caloric restriction in improving insulin sensitivity or how efficiently cells can move sugar out of the blood.^{8, 9} Further, IF can improve blood sugar and glycemic response without any other changes or dietary restrictions.¹⁰

The timing of the fast may also come into play, as one study found that an IF pattern where the first meal was earlier in the day improved beta-cell responsiveness (the cells in the pancreas that make insulin), insulin sensitivity, and markers of oxidative stress compared to a group eating later during a 12-hour window.¹¹

3. Intermittent Fasting May Support Healthy Aging

Fasting could support longevity and healthy aging. More research is needed, but animal studies show that fasting can increase life expectancy.² The effect on longevity is likely related to autophagy, which cleans out damaged cells to reduce oxidative damage, a potential root cause of the aging process and age-related health conditions.¹²

4. Intermittent Fasting Could Protect Your Brain

Once again, the power of autophagy extends to brain cells by removing aging and damaged cells, which could decrease the risk of neurological diseases.¹³ Inflammation (aka inflammaging) is also closely associated with the aging process. Fasting is also linked to improved cognitive function, including memory and neurodegeneration.¹⁴

5. Intermittent Fasting Is Heart-Healthy

IF may also offer cardiovascular protection with or without weight loss by lowering cholesterol, blood pressure, and triglycerides.¹⁵ As mentioned earlier, the inflammatory markers associated with increased risk of cardiovascular diseases are positively affected by intermittent fasting.¹

<p class="pro-tip"><strong>Also Read: </strong><a href=”is-fasting-good-for-diabetes">Is Intermittent Fasting Good For Diabetes? Unveiling Answers</a>.</p>

Is Intermittent Fasting Safe for Everyone?

Fasting can be safe for nearly everyone because it can be adapted to your lifestyle. However, it's possible to take any diet alteration too far. Extended fasts are a slippery slope to disordered eating habits, especially if followed very rigidly.

The good news is that you don't have to be overly restrictive, as simply fasting for 12 hours overnight still provides benefits. Most people do well within the 12- and 16-hour fasting window, but it's important to listen to your body.

Signs you've gone a bit too long include fatigue or hunger to the point of dizziness or nausea or simply not feeling well. The goal of IF is to help you feel good, so if it's not working for you, don't force it.

There are several contraindications to fasting, including:

• Pregnancy or breastfeeding
• History of eating disorder
• Underweight
• Reactive hypoglycemia

If you are taking any medications, especially those for diabetes that affect your blood sugar, it's essential to check with your doctor before fasting. Children or older adults should not participate in extended fasts as well.

Intermittent Fasting and Women’s Hormones

It's always crucial to note that women may respond differently to fasting than men because of hormones. Women's bodies and hormones are susceptible to perceived stress from nutrient scarcity, so a side effect of restriction of any kind, from calories to prolonged fasting, is hormone imbalance that can adversely impact a woman's menstrual cycle.^{16, 17}

Does this mean all women shouldn't fast? No, many women fast and see a lot of benefits. But depending on how your body responds, you may need to adjust the length of your fast or how many days you do it. Always pay attention to the signs your body gives you, and if you notice any changes to your cycle, it's time to make adjustments or stop fasting altogether.

Getting Started With Intermittent Fasting

If you're brand new to IF, here are some helpful tips to get you started:

• Plan ahead and think about what you'll eat to break your fast, as well as the rest of the day. If you're hungry, you are more likely to make an impulsive choice, even if it's not the healthiest option. Make sure that the first meal has fiber, fat, and protein to balance your blood sugar and energy response.
• Don't restrict yourself during your eating window. Make sure you eat enough food during your eating window. Overrestricting means you'll be more hungry while fasting, and it adds unnecessary stress to your body.
• Choose nutrient-dense foods. Food quality still matters because it provides essential vitamins, minerals, and phytochemicals. Avoid processed and packaged foods and reach for whole foods like vegetables, fruits, legumes, nuts, and seeds instead.

Above all, start slow and listen to your body. Diving into an extended fast is not a great idea if you're new to fasting, but an overnight fast is a great place to start. You may find that it fits perfectly with your lifestyle, or you can try to extend it a bit if it works for you.

Frequently Asked Questions

Which Version of Intermittent Fasting Is the Most Effective?

There is no one most effective version of IF because everyone’s body responds differently. The most effective pattern is the one that fits best with your lifestyle, helps you reach your health goals, and doesn’t overstress your body.

What Is the Difference Between 16-8 and 14-10 Intermittent Fasting?

16-8 and 14-10 refer to the time spent fasting and eating. For 16-8, you fast for 16 hours and have an 8-hour eating window, while 14-10 requires fasting for 14 hours with a 10-hour eating window. The main difference is the length of the fasting period.

What Is the Best Intermittent Fasting Schedule to Lose Belly Fat?

You can't spot reduce fat from areas of the body, so there is no specific IF schedule that targets belly fat. However, overall weight loss can reduce inches around the abdomen, and incorporating exercise with your IF schedule could help build muscle and tone the area.

Does Coffee Break a Fast?

Black coffee without any cream or sweeteners won’t break your fast. IF purists may argue that anything other than water breaks a fast, but small amounts of black coffee are generally accepted in most IF protocols.

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<p class="pro-tip"><strong>Learn More: </strong><a href="impaired-fasting-glucose">How to Improve Impaired Fasting Glucose</a>.</p>