Intermittent fasting has soared in popularity lately, securing it a slot as one of the hottest health trends within the last few years.
While it may sound like little more than a fad diet, intermittent fasting has actually been practiced for thousands of years and is considered a key component of many major cultures and religions. Plus, recent research has found some pretty impressive benefits about this distinct eating pattern, ranging from reduced inflammation to better brain health and beyond.
In addition to being incredibly flexible, it’s also effective and easy-to-follow, making it easy to see why it’s gained such widespread attention from dieters and health experts alike. And with popular variations such as The Warrior Diet and keto fasting gaining rapid momentum, it seems that intermittent fasting is here to stay for quite some time.
In this comprehensive intermittent fasting guide, we’ll cover everything you need to know about this popular eating plan, including how to determine whether or not it’s right for you.
What is Intermittent Fasting?
Intermittent fasting is an eating pattern that involves cycling between periods of eating and fasting for specific blocks of time. This can vary quite a bit based on the style of intermittent fasting; in some cases, you may abstain from food altogether for a certain period, while in others, you may cut back on calories or limit your intake to a few specific food groups.
Although it’s unclear exactly why intermittent fasting is so beneficial for the body, research suggests that it may work at a cellular level. In particular, it’s believed that intermittent fasting helps reduce oxidative damage to the tissues while also protecting the cells against the harmful effects of stress (1).
Despite only recently emerging into the limelight, intermittent fasting has actually been around for quite a while. In ancient times, humans practiced fasting when food sources were scarce. Fasting is also central to many religious practices such as Ramadan, a month during which Muslims fast from dawn until sunset in order to strengthen self-discipline and practice spiritual reflection.
Today, some combine different diets with fasting in an effort to amplify results. On the ketogenic diet, for example, fasting is thought to speed up the transition to ketosis, which is a metabolic state that helps your body burn fat for fuel instead of glucose. Although intermittent fasting on keto is not necessary, it may help reduce symptoms during this transition, which can include headaches, fatigue, and irritability.
Many also enjoy intermittent fasting for the flexibility it offers those looking to improve their health without the rules and regulations that accompany many other popular diets.
Types of Intermittent Fasting
There are plenty of different styles of fasting out there, each of which can vary based on the required intermittent fasting times and days throughout the week. These can range from fasting every other day to completing a 16 hour fast just a few times per week.
Here are a few of the most common types of intermittent fasting:
- Alternate-Day Fasting: As its name implies, this eating pattern involves fasting every other day. On fast days, you’ll eat either a very small amount or abstain from food altogether. On the other days during the week, you can enjoy a normal diet rich in healthy, nutrient-rich ingredients.
- 16/8 Diet: This type of fasting entails limiting your food intake to an eight-hour block of time each day. Although you can customize your intermittent fasting hours based on your own schedule, most people find it easiest to simply stop eating after dinner and skip breakfast the next morning.
- 5:2 Diet: This diet allows you to follow a normal, healthy diet for five days out of the week. On the remaining two days, you should cut your intake to around 500-600 calories per day.
- Eat-Stop-Eat: With this method, you pick one or two non-consecutive days during the week and abstain from eating for 24 hours straight. During the other days, you can eat normally as you would throughout the week.
- The Warrior Diet: On this plan, you should only eat fruits and vegetables during the day, followed by one large meal each evening.
Benefits of Intermittent Fasting
1. Promotes Blood Sugar Control
Several studies have found that intermittent fasting can be an effective strategy to help support healthy blood sugar levels. In fact, one study evaluated the effects of fasting during Ramadan in 20 healthy men and showed that blood sugar levels declined by 12% over the course of the entire month. Not only that, but they also experienced an increase in insulin sensitivity, as insulin levels decreased by a whopping 53% (2).
Insulin is the hormone responsible for shuttling sugar from the bloodstream into the cells, and decreasing circulating levels of insulin can be incredibly beneficial when it comes to blood sugar control. This is because having high levels of insulin–often due to factors like an unhealthy diet or physical inactivity–can cause your body to become less sensitive to its effects, translating to higher blood sugar over time (3).
2. Supports Healthy Weight Maintenance
Many people have started using intermittent fasting for weight loss, and for good reason. Multiple studies have found that fasting can reduce body fat and rev up weight loss to support weight management. According to one study, 3-12 weeks of alternate-day fasting was effective at reducing body weight by up 7% and increasing fat loss while also improving cholesterol and triglyceride levels (4).
Plus, other research shows that fasting can reduce levels of leptin, the hormone responsible for promoting feelings of fullness and satiety (5). While this may sound counterintuitive for weight loss, it can actually be effective at combatting leptin resistance, ensuring that your body is able to use this hormone more efficiently to keep your appetite in check.
3. Boosts Brain Health
In recent years, researchers have continued to solidify the close link between food and mental health, demonstrating that what you put on your plate could play a key role in regulating focus, attention span, memory, and more. Interestingly enough, a 2015 animal study actually showed that chronic interval fasting actually improved several markers of cognitive function, including learning and memory (6). Similarly, another study found that intermittent fasting preserved brain function by reducing inflammation (7).
As of now, however, most research on the potential impact of interval fasting for brain health is limited to animal studies and test-tube trials. More studies are needed to determine whether intermittent fasting can actually improve brain function in humans.
4. Relieves Chronic Inflammation
Inflammation is a normal response by the immune system and an important one at that. It protects the body against foreign invaders and helps prevent illness, infection, and injury to the cells.
Chronic inflammation, on the other hand, can actually be harmful, with some research indicating that it could even contribute to the development of serious conditions like heart disease and cancer. It can also cause the immune system to attack healthy cells in the body, triggering symptoms of autoimmune conditions like rheumatoid arthritis and inflammatory bowel disease (8).
Some studies show that intermittent fasting could be beneficial for easing inflammation to support better health. For example, one trial conducted in Saudi Arabia showed that fasting during the day was linked to lower levels of several proteins used to measure inflammation, including IL-1β, IL-6, and tumor necrosis factor α (9).
5. Enhances Heart Health
Responsible for pumping out about 75 gallons of blood every single hour, there’s no question that the heart is one of the most important organs in the body (10). When paired with a nutritious diet and active lifestyle, intermittent fasting can be an effective tool to defend against heart disease and help keep your heart healthy and strong.
One study actually found that fasting for four weeks led to improvements in cholesterol and triglyceride levels as well as reductions in systolic blood pressure and belly fat, all of which are major risk factors for heart disease (11). As if that wasn’t enough, another study also showed that intermittent fasting significantly increased survival rates by nearly four-fold in rats who suffered a heart attack (12).
So is intermittent fasting right for you? Despite the impressive set of benefits associated with this popular eating plan, it’s definitely not a good fit for everyone.
For example, if you have diabetes, you should talk to your doctor before starting intermittent fasting, as going long periods without eating can cause dangerous dips and spikes in blood sugar levels.
Furthermore, intermittent fasting for women who are pregnant or breastfeeding is also not recommended, as it could potentially increase the risk of nutritional deficiencies or problems with fetal growth and development. Instead, it’s best to work with a registered dietitian to help achieve your health goals while providing your body with the nutrients it needs throughout the day.
Fasting for long periods is also not recommended for women, as it may disrupt the secretion of certain hormones, which can lead to irregular periods, infertility, and a slew of other negative effects on health (13, 14). Therefore, it’s best to practice intermittent fasting in moderation and stick to shorter periods of fasting with fewer fasting days to maximize results.
Intermittent fasting is also not recommended for children and teenagers, those with a history of eating disorders, or those with health issues such as thyroid problems or gallstone disease, as it could worsen these conditions.
Whether you’re a competitive athlete or casual gym-goer, it’s also important to listen to your body and avoid pushing yourself too hard; while moderate activity is typically fine during intermittent fasting, try to build your workout routine around the days that you’re eating regularly. If you start feeling sluggish or shaky when you start intermittent fasting, try having a small snack and a glass of water to see if symptoms subside.
Finally, keep in mind that intermittent fasting isn’t a substitute for a healthy diet. Even with fasting, it’s still important to be sure that you’re getting lots of nutrient-dense foods in your diet to optimize health.
Whether you’re looking to improve blood sugar control or fasting for weight loss, intermittent fasting is a popular practice that can be beneficial to several aspects of health. There are also several unique variations of the plan, which make it easy to find a type tailored to your specific needs.
If intermittent fasting works for you, that’s great. However, it definitely isn’t for everyone, and it’s not always necessary to achieve better health. In fact, most can improve overall health by simply following a nutritious, well-rounded diet and engaging in regular physical activity.