Fact checked by Aimee McNew for Accuracy
There are many tricks to promote weight loss, but intermittent fasting (IF) isn’t a joke.
It’s become increasingly popular in recent years and for good reason. Research shows it has plenty of benefits, but that still doesn’t mean it’s good for everyone.
How do you know if it’s right for you? Read on.
What is Intermittent Fasting?
Intermittent fasting is a specific pattern of eating designed to promote fasting benefits without denying yourself food for more than 24 hours.
It is different from strict fasting, which might eliminate all or most foods for a certain number of days. Fasting can be dangerous and should not be attempted without medical approval.
Intermittent fasting, however, implies daily food intake. Instead of eating throughout the day, however, your total food intake is contained to a specific window.
For example, many intermittent fasters skip a traditionally-timed breakfast and don’t eat first until noon and then end their last meal of the day by 7pm.
Intermittent fasting is a protocol that does not tell you what to eat, but rather when.
Types of Intermittent Fasting
Intermittent fasting can be done in many different ways. These are the most common methods for using IF.
The 5:2 Diet
This doesn’t involve long periods of no food but instead refers to extreme caloric restriction on two days of the week. For five days you eat normally, and for two non-consecutive days you eat fewer than 1,000 calories, which is typically two smaller meals.
You should get medical clearance before you fast this way.
Also known as eat-stop-eat fasting, this type involves not eating from dinner one day until dinnertime the next. So you don’t go an entire day with no food, but you do give your digestive system a 24-hour break.
This is typically done one or two times per week, with normal eating patterns the other days of the week. You should get medical clearance before you fast for 24-hours at a time.
The 16/8 Method
With this protocol, you skip breakfast and only consume food for about eight hours each day. Some people choose from 12 pm to 8 pm, or from 1 pm to 9 pm, but others will also restrict food consumption to six or seven hours.
This method reduces snacking in the evening and capitalizes on the already normal fasting time while you are asleep.
This method is also referred to as the lean-gains protocol, and even though it’s less extreme, you should still check with your doctor before trying it.
The 16/8 method or others close to it are the most popular ways to do intermittent fasting.
8 Benefits of Intermittent Fasting
Research has examined many angles of intermittent fasting and discovered several key benefits. Not only can it promote weight loss, but it can promote cognitive wellness, and it might even lengthen your lifespan. (1, 2)
These are the top proven reasons why IF might be beneficial for health.
1. Weight Loss
Eating less will naturally lead to weight loss in most cases.
Intermittent fasting works for weight loss in several ways, but one of them is by restricting the time of eating, it results in less mindless snacking and excessively large meals. (3)
During the time that you’re not eating, such as a 16 hour fast from dinner until lunchtime the next day, your body dips into stored glucose and fat for energy, resulting in more energy expended than being stored.
This translates to fat loss. However, if your meals when you do eat are not high enough in protein, you could end up burning muscle for energy during times of fasting, so it’s important to eat a well-balanced diet for the best long-term results.
Intermittent fasting can also be helpful for shrinking the waist as research has found that it can reduce belly fat.
Belly fat is dangerous because it surrounds the organs in your trunk and can lead to several types of disease including diabetes and heart disease. (4)
Part of the reason we lose weight is because of metabolism.
Regulated by the thyroid and other hormones, metabolism sets the baseline for how much energy your body needs just to be awake and functioning.
When your basal (or baseline) metabolic rate is higher, you naturally burn more fat and calories just by being up and around. Intermittent fasting can help to boost your basal metabolic rate. (5)
Intermittent fasting can boost your basal metabolic rate by as much as 14 percent. (6)
This can lead to a greater loss of weight than simply counting calories. Research shows that by using IF, you can lose up to eight percent more body weight over six months. (7)
3. Epigenetic Improvements
You are born with one set of genes that don’t change. But what can change is how your genes work or express themselves. Epigenetics is the process by which your genes are influenced by the environment around you.
This includes your living space and the air you breathe, but also diet, exercise, and overall lifestyle, like whether you get enough sleep or are too stressed on a regular basis.
Intermittent fasting helps to promote cell repair and also boosts the function of genes that promote longevity. It can help to turn off epigenetic expression that is associated with inflammation and disease, too. (8, 9, 10, 11)
4. Insulin Sensitivity
Insulin is a hormone that helps take glucose into your cells to be used as fuel. When the body becomes resistant to insulin’s activity, insulin resistance develops and blood sugar levels get too high.
This is often the case with type 2 diabetes and metabolic syndrome. The more optimized your insulin levels, the better your body can use fat for energy, and the closer your weight will be to optimal. (12)
Intermittent fasting has been shown to reduce blood sugar by as much as six percent and fasting insulin levels by as much as 31 percent. (13)
5. Human Growth Hormone
Inflammation is typically a healing response in the body, but when it becomes chronic, it can lead to negative consequences. IF can help to regulate inflammation levels in the body and reduce problems related to systemic inflammation. (16)
7. Cardiovascular Health
Heart health is benefitted by intermittent fasting. While all cholesterol isn’t bad, when LDL cholesterol becomes oxidized it can sit in the arteries and lead to inflammation, plaque build-up, and eventual blockage.
8. Cognitive and Neurological Health
Intermittent fasting can support a healthy brain and cognitive function. It can even promote the growth of new nerve cells as well as increasing brain-derived neurotrophic factor (BDNF), which is a protein that promotes healthy brain cells.
Who Should Not Practice Intermittent Fasting?
As with most things, not everyone gets the same benefits from certain diets or dietary protocols. Intermittent fasting can have dramatic improvements in health in some people but would not be a good idea for others.
Certain people should not try intermittent fasting because they need a more steady nutritional intake for proper growth or development or this pattern of eating would be detrimental in some other way. These include:
- Anyone under age 18
- Anyone who is underweight
- Anyone who has ever experienced an eating disorder
- Anyone who has a diagnosed medical condition of any kind
- Anyone who has type 1 or type 2 diabetes
- Pregnant women or women trying to get pregnant
- Anyone with low blood pressure
- Women with a history of menstrual problems
- Women who are breastfeeding
- Women with thyroid disorders
Even if you don’t fall under any of those categories it is a good idea to check with your doctor before starting a new dietary protocol. Nothing replaces the benefit of personalized medical care.
There is also some research that shows that IF may not be the best idea for women overall as directly compared to men. Most studies look at how IF affects men, and that cannot be universally applied to women.
In some other studies, intermittent fasting was shown to actually cause more problems for women, like worsening blood sugar levels or insulin sensitivity or leading to menstrual disorders or even problems getting pregnant. (23)
This doesn’t necessarily mean that women cannot practice IF, but they may need to ease into it more slowly or fast for shorter periods of time. Some tips for women to start intermittent fasting include:
- Fasting for 10-12 hours, at most 14, instead of 16 to 24
- Monitoring thyroid and reproductive hormones throughout the cycle to ensure they are not being suppressed in response to fasting
- Working with a nutritionist to ensure that when they’re eating, they are meeting all nutritional requirements and not contributing to deficiencies or unhealthy relationships with food
What Counts As Breaking the Fast?
If you’re practicing intermittent fasting, you might want to know what you can do during fasting periods versus eating times.
You can (and should) drink plenty of fluids during non-eating times. These include water, black coffee, tea, and sparkling water. Basically liquid without calories. Caffeine does not count.
If you are looking to do a less intense version of IF, you can also include bone broth and soup stock during periods of fasting so that you’re getting a few calories, but your digestive system still isn’t having to work too hard.
You can also add collagen peptides to coffee or beverages during fasting time without breaking the fast.
Is Intermittent Fasting Right For You?
If you are interested in the idea of intermittent fasting and have no underlying medical conditions or reasons why it is not a good idea, it may be an interesting experience. You may feel better and be able to lose some weight.
However, intermittent fasting is not a magic bullet and should not be attempted to lose extreme amounts of weight quickly or to otherwise engage in unhealthy eating behaviors.
It’s most important that you eat a balanced diet and meet all of your body’s nutritional needs. This can be done with or without intermittent fasting and needs to be the primary focus.
If the idea of fasting in any form seems stressful or undesirable, then don’t do it. Unless your doctor has specifically recommended intermittent fasting, you don’t need to do something that will make you feel miserable about how or when you eat.
There are many ways to approach healthy eating.
Intermittent fasting is one approach for eating in a way that may have some health benefits, like insulin sensitivity, weight loss, and cardiovascular health.
However, there are many ways to achieve these health benefits and intermittent fasting is not the only answer.
IF can be a great way to optimize a relationship with food and eating, but for others, it may have negative consequences.
Ultimately, a person’s relationship with food is highly individualized and should be considered. Nothing is one size fits all.
This article was fact checked for accuracy by Aimee McNew, MNT, a certified nutritionist. As always, this is not personal medical advice and we recommend that you talk with your doctor.
Aimee McNew, MNT, CNTP, is a certified nutritionist who specializes in women’s health, thyroid problems, infertility, and digestive wellness. She ate her way back to health using a Paleo diet, lost 80 pounds, and had a healthy baby after numerous miscarriages. She focuses on simple nutrition practices that promote long-lasting results.