9 Types Of Intermittent Fasting + How To Know Which One Is Right For You

There are a number of fasting programs to choose from, which can make it difficult to know which one is right for you. In this article, we break down different types of IF and chat with experts about the benefits and possible risks of IF to help you decide whether IF could benefit your health.

There are a few different types of IF programs1 to choose from, but they all have one thing in common: abstaining from calories over a set period of time. There are some programs that involve eating a small number of calories rather than not eating at all, but those are considered "modified2" fasts and differ from traditional types of IF.

Autophagy is the process by which your cells break down and destroy damaged, old, or abnormal substances, like proteins. Autophagic activity decreases with age5, so IF may be an effective way to improve cellular health and improve longevity as well.

Here's a little more about the types of IF and modified fasts that are currently most popular, including pros and cons, and who they'd benefit most:

"I believe the best fasting method for weight loss is whichever one someone can stick to indefinitely," Tinsley tells mindbodygreen. "Since sustainable weight loss and long-term weight loss maintenance should be the goal of those seeking to lose weight, a conservative but feasible program is preferred over an extreme, short-term program. While more extreme fasting programs can lead to additional weight loss in the short term, they don't typically help in establishing long-term habits in the same way a more balanced, conservative program can." 

However, it's inappropriate for some people, including children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders, and people who are underweight.

One randomized controlled trial11 found that when participants with obesity went on a calorie-restricted diet, those who took in more calories at breakfast and lunch and fewer at dinner lost more weight and experienced higher reductions in blood pressure than those who ate more calories later in the day. Fasting in the hours leading up to bed can also help improve your sleep.

Circadian fasting is another eating strategy that is suitable for IF beginners. Those who are prone to unhealthy late-night snacking might find it especially beneficial. It's inappropriate for children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders, and people who are underweight.

This type of fasting is associated with all the benefits of TRF, and research finds that eating within an eight-hour window might lower blood pressure12 too.

It's inappropriate for some people, like children, pregnant and breastfeeding women, those taking certain medications, and people who are underweight.

When followed for eight to 12 weeks16, ADF has been shown to decrease LDL cholesterol by as much as 25% and triglycerides by as much as 30%.

Since ADF is a more restrictive type of fasting, you should consult with your doctor before giving it a try. It's inappropriate for some people, like children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders19, and people who are underweight.

It's been shown to be effective in promoting weight loss18 and reducing certain inflammatory markers, like high-sensitivity C-reactive protein (hs-CRP). 

While this type of fasting is slightly more approachable than strict ADF, you'll still want to talk to your doctor before trying it. It's inappropriate for some people, like children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders, and people who are underweight.

A 12-hour fast is a type of TRF in which you consume all of your calories within a 12-hour window and then fast for 12 hours. This is the least restrictive type of TRF because it allows for a fairly normal eating pattern. Still, it may help you reduce your overall calorie intake, which can help you lose weight and improve your metabolic health. 

This 12-hour fast is a safe way to dip your toes into fasting if you're a beginner. You'll want to stick with a circadian-friendly eating pattern (where you restrict calories in the evenings close to bedtime) for the best results. It's generally safe for most people since it mimics our natural eating patterns.

During the fasting days, energy intake is typically kept to around 600 calories. Studies show that the 5:2 diet may be helpful for weight loss21 and improving certain health conditions, like nonalcoholic fatty liver disease22 (NAFLD). Learn more about how to do it here.

Since 5:2 fasting is a more restrictive type of fasting, you should consult with your doctor before giving it a try. It's inappropriate for some people, like children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders, and people who are underweight.

Because modified fasts that allow for some calorie intake during fasting windows seem to offer some health benefits—like weight loss—it's likely that dirty fasting does, too—as long as you don't go overboard. Learn more about dirty fasting here.

Those who have trouble sticking with strict fasting plans may benefit from the less rigid approach of dirty fasting. Dirty fasting is inappropriate for children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders, and people who are underweight.

A 24-hour fast is a type of PF where you consume zero calories for 24 hours. Some people fast for 24 hours a few times a month, while others use this method once or twice per week. This method could help you lose weight23 and improve other aspects of health, but it can be difficult to stick to. Learn more about 24-hour fasting here.

Since 24-hour fasting is a more restrictive type of fasting, you should consult with your doctor before giving it a try. It's inappropriate for some people, like children, pregnant and breastfeeding women, those taking certain medications, people with eating disorders19, and people who are underweight. For those with Type 1 diabetes, this type of fasting may throw off blood sugar levels.

A 2021 study26 published in the Journal of Translational Medicine found that following a 16:8 fasting regimen for six weeks led to significant improvements in body weight, menstrual cycle irregularity, insulin resistance, and testosterone levels in women with PCOS. 

According to Jason Fung, M.D., a nephrologist and intermittent fasting expert, fasting may be beneficial for concentration and memory. "There is limited research on fasting and brain health, although theoretically, it may be beneficial," he tells mindbodygreen. "Insulin resistance, obesity, and metabolic syndrome are all associated with cognitive decline...and fasting reduces those conditions. In the short term, fasting may improve concentration, memory, and other cognitive functions because of the increase in sympathetic tone31."

If you have questions about IF, consider speaking with a trusted health care provider. They can help you decide if IF is right for you and can help you choose a safe IF program. If you're new to fasting, these tips can make it a bit easier.