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Intermittent fasting or IF has taken the health and dieting world by storm over the past few years, with more and more followers sharing their remarkable journeys to improved weight loss. 

While many people try intermittent fasting to help shed excess pounds, others use it because of its health benefits or because of how it helps to simplify their lifestyle. 

But what is intermittent fasting, and what exactly does it do to your body and mind? Those and many more questions are answered in this beginner’s guide to fast and healthy weight loss with intermittent fasting. We explore the ins and outs of this way of eating, including what science tells us about how ‘IF’ can help you achieve speedy weight loss, live longer and think more clearly. 

Understanding Intermittent Fasting

Intermittent fasting is basically a way of eating that requires you to go for more extended periods between eating and to consume food only within a prescribed, shorter window of time. There is no specific eating plan with IF, and you can use it with any type of meal plan, including keto, whole-foods, clean eating, or whatever floats your boat. Because it is not about WHAT foods you eat, it is not a traditional diet but could be looked at to improve your eating habits, no matter what you consume.

There are many variations to intermittent fasting, which we explore more in-depth below, but the most common window is referred to as 16:8, which means 16 hours of fasting while eating all your food for one day in an eight-hour window.

Fasting has been used across cultures for various purposes for thousands of years. While some types of fasting are forced, because of a lack of food, others are performed as a part of religious or ceremonial rituals. Our ancient predecessors were often without food during the hunter-gatherer phase of our evolution, so our bodies are conditioned to go without food for extended periods. It is only within the more abundant 20th century that people on our planet began to expect and assume food to be available to them several times per day (especial in the western world).

Our bodies would argue that fasting is more natural and optimal for its function than eating three or four times per day, and those who practice IF would agree. Many who choose this way of eating report improvements in their health beyond weight loss, and they continue to adhere to a fasting schedule long after they have reached their goal weight.

Weight Loss with Intermittent Fasting

Most people try intermittent fasting because they want to lose weight. Because you are eating fewer meals per day, you are almost surely eating less when you fast for longer periods. This reduction in caloric intake leads facilitates weight loss.

In 2013, researchers at Harvard Medical School showed that caloric restriction, such as with fasting, can increase the lifespan and improve metabolic functions in mammals, including people. This and other animal research provide a wealth of convincing evidence, but more research was needed to examine the effects of fasting on humans.

Two separate reviews in 2015, researchers from Utah and Texas examined the effects of IF (intermittent fasting) on humans and independently concluded that this way of eating has positive effects. These include reductions in LDL cholesterol, triglycerides, blood pressure, weight, fat, and glucose levels, all of which are associated with improved health.

Some would argue that intermittent fasting could lead to increased calorie consumption during the times when dieters are allowed to eat, but these same researchers did not find that to be true. In a systematic review of clinical trials using IF, researchers learned that IF resulted in a typical weight loss between seven and eleven pounds over ten weeks. This review showed that:

  • Dropout rates for IF were similar to those on a traditional diet of calorie restriction as was the final weight loss result. That means fasting may not be any easier than regular dieting, but it is as effective. 
  • Those who engaged in intermittent fasting did not have any overall increase in their appetite, as some might expect with more extended periods of not eating. 
  • When compared with other types of diets, intermittent fasting is just as effective at reducing weight and has comparable results for long-term maintenance.

Other studies have shown more dramatic results, though. For example, a 2014 study examining the effects of IF on patients with Type 2 diabetes showed that participants lost significantly more weight with intermittent fasting than with other types of dieting. They were more likely to lose belly fat, which is an indicator of improved health and lower risk for chronic disease, as well.

A 2018 study, published in Nutrition and Healthy Aging, found that obese people who adhered to the 16:8 protocol at about 350 fewer calories per day and lost three percent of their body weight in 12 weeks. Other researchers have examined alternative fasting schedules, as well.

In a recent study in The American Journal of Clinical Nutrition, researchers found that obese patients who had unrestricted eating for five days followed by two days of significant caloric restriction lost more weight than those who had calorie restrictions every day. After one year, though, the results for the two groups were the same.

So, how does IF help you lose weight? And are there other health benefits or drawbacks to this way of eating? Let’s take a closer look at how fasting affects the body and the mind.

Health Benefits of Intermittent Fasting

There are numerous studies indicating that fasting can improve metabolism and delay the effects of aging on the human body. Fasting does not just change how much you eat; it changes how your body processes food for energy, and it can even influence how your brain functions over time.

Effects of Fasting on Hormones and Cells

Fasting results in several effects on the body at the cellular level. For example, fasting leads to improved insulin sensitivity, which can help you keep your levels of insulin lower. This drop can promote better burning of stored body fat, according to a 2005 study.

In addition to helping your body use glucose and insulin more effectively, fasting boosts your production of human growth hormone (HGH). Higher levels of this hormone, according to The New England Journal of Medicine, is associated with an increase in lean body mass and a reduction in adipose tissue, also known as belly fat.

These two hormonal influences can help increase your ability to burn fat, which can lead to improved weight loss. But that is not where the benefits of fasting end. When you fast, your cells move into a state of repair and rejuvenation, including recycling damaged cells and forcing the death of old and dysfunctional ones. The phenomenon of cellular repair, as noted by researchers from California in 2010, results in healthier, more energetic cells being left behind, which can help you live longer.

Related to aging, fasting also can lead to changes in how specific genes related to longevity function. Researchers at the University of Chicago discovered in 2013 that fasting helps to prevent cancer as well as slow the growth of tumors. A 2006 study from Aging Research Reviews noted that fasting led to improved brain function and less neuro-degeneration associated with aging.

Effects of Fasting on Heart Health

According to a 2007 study, alternate-day fasting, a form of intermittent fasting, was shown to reduce markers of inflammation in the body. Inflammation is a driving factor behind many chronic diseases, including heart disease. Researchers in Turkey noted similar effects, including a reduction in many biochemical risk factors associated with cardiovascular disease. Additional research in 2009 and 2013 further illustrated that fasting improves your heart by lowered LDL cholesterol, triglycerides, blood glucose, and inflammatory markers that are known to contribute to poor heart health.

Effects of Fasting on the Brain

Not only can fasting help your body, but it also can help improve your brain health. Intermittent fasting, for example, is associated with a reduced risk for developing neurodegenerative diseases such as dementia, according to a 2007 study. Part of these effects are due to the reduction in weight and protection against diabetes, both of which increase your chances for developing these diseases.

But intermittent fasting also helps to protect against degeneration at the neuron level. One 2003 study showed that IF helps protect brain cells from neuronal death. Researchers from The Scripps Research Institute also discovered that short-term fasting boosts autophagy in the brain, which is the process of accelerated death and recycling of damaged cells, which facilitates new cell growth.

Intermittent fasting can help boost your memory, too. A 2009 study showed that older participants were able to improve their recall of words after just three months of IF eating. And, intermittent fasting can help with mood disorders, such as depression, according to a study published in Psychiatry Research.

Effects of Fasting on Stress

Maintaining healthy habits can be difficult, and healthy eating takes time to plan and prepare meals. When you use intermittent fasting, it simplifies your life and allows you to focus on other aspects of your lifestyle for more significant portions of your day.

When you do not have to prepare and clean up after so many meals, you have more time to devote to other aspects of your life, which can reduce your stress level and help you enjoy life more. Many people find that fasting leads to them thinking or worrying about food less, which can help them focus on other parts of their health.

Getting Started with Intermittent Fasting

There are many ways to use intermittent fasting, and you may have to try a few before you discover which works best for you and your body. The basics of IF involve splitting each day or week into periods of eating and fasting.

During fasting times, you consume only beverages that do not contain any calories or through your body out of the autophagy (cell recycling) phase. For most people, this includes water, black coffee or tea, and small amounts of bone broth. There are many arguments about how much you can eat or drink and still remain in this phase of cellular repair, but for beginners, your best bet is just not to eat anything.

Common Intermittent Fasting Methods

  1. 16:8 Method- Restrict your eating to an 8-hour period each day, such as from noon- 8 pm. You can adjust your window to your lifestyle. For example, those who rise at 6 am may want to break their fast earlier in the day and quit eating before evening. You may eat two or three meals within your window as you wish. You can adjust the window slightly, with some preferring to fast for 14 hours and others for 20.
  2. 5/2 Method- Restrict your eating two days a week to between 500-600 calories and eat normally the remaining five days. Some find this harder than others or experience slower weight loss. There are no research studies on this specific type of IF schedule, but it does fall in line with other types of fasting in terms of caloric restriction.
  3. Eat-Stop-Eat Method- This approach requires you to fast for 24 hours one to two days per week. You can choose to fast from dinner one day to dinner the next or from breakfast to breakfast; which is best for you is fine. You may drink non-caloric beverages, but you cannot consume solid food. Eat normally the other days of the week. Some people find a 24-hour fast to be difficult. You can ease into it by starting with a 14- or 16- hour fast and working your way up to a full day.
  4. Alternate-Day Method- This method has a few variations. It is basically fasting every other day, which can mean eating nothing at all to consuming 500 calories on fast days. Some even do 16:8 on fast days and normally eat the others. There are many studies on this type of alternating fast, which is quite effective.
  5. The Warrior Method- This diet is a variation on the 20:4 fast. Instead of eating nothing during the day, though, you consume small amounts of raw produce. During your eating window, you have one large meal. Food choices in this method are usually restricted to whole foods and unprocessed options.

Many people naturally like to skip meals or do not eat breakfast, which is a type of intermittent fasting, as well. Those with diminished appetites due to a low-carb diet, certain medications, or metabolic disorders may regularly practice IF without even realizing it. Most people have few issues adopting the 16:8 window because it fits nicely into the daily routine and you can still get plenty to eat during the eating window.

Tips for Getting The Most from Your Intermittent Fast

So, have decided to try intermittent fasting! Great!! If you want to get the most from your fasting experience, including successful weight loss, then there are a few things you can do to stay on track and make your experience more enjoyable. Here are the top tips for maximizing your benefits from intermittent fasting.

  • Stay hydrated. You should still be drinking plenty of fluids, especially water. Other good options include herbal tea, sparkling water, or black coffee in moderation. Be sure you are drinking throughout the day.
  • Make your calories count. Fasting is not permission to go nuts during your eating window. You should be eating healthy, nutrient-dense foods. You need plenty of fiber as well as healthy fats and protein. Since you are eating less, everything you put in your mouth should be good for you and full of nutrients.
  • Eat for volume. Foods that are low in calories but high in volume will fill you up without adding to your waistline. Vegetables, fruits with lots of water, and popcorn are examples of these types of foods.
  • Avoid processed foods and added sugars. When you break a fast with high-calorie foods with lots of sugar or carbs, you will immediately raise your blood sugar and probably feel bad.
  • Take it slow. Start small and work your wat up to more extended periods of fasting. You may need to move your eating window in small increments until you get it where you want it. Give your body time to adjust, and you will be more likely to stick with it.
  • Pay attention. Become more observant of your body, how hunger makes you feel, the effects of longer periods of fasting, and how certain foods influence you. The more you pay attention, the more informed choices you can make. Because you are eating for less of the day, you can afford to devote more time to how eating makes you feel.
  • It takes time. Not everyone adjusts easily to fasting. Give it time. If this is something you want to use to lose substantial amounts of weight, then it will take a while, so do not let the first few weeks of adjustment scare you off.
  • Expect setbacks. We all have ups and downs. It is part of the process. What you can learn from your setbacks is more important than having them.
  • Distract your mind. When you find yourself thinking about food a lot, find ways to occupy your mind until your next eating window. Engage in a hobby, go for a walk, or talk to a friend.
  • Take a rest day. When you find that life is getting in the way, take a break from fasting for a day and eat as you usually would. Then, get back on track the next day.
  • Find a plan that works for you. There are so many ways to fast intermittently that your experience may be completely different from someone else’s. That’s okay. You do not need to have the same schedule as anyone else. Figure out what is best for you. Adjust as you need. What is important is that you are comfortable, and you are getting the results you want.
  • Learn the difference between boredom and hunger. Often, we eat because we have nothing else to do or because we are avoiding things we do not want to do. Learn to identify genuine hunger during your fasting periods. How does it feel in your stomach? How does it feel in your brain? Eat when you are actually hungry, and you will enjoy better health overall.
  • Find support. If others in your life do not understand or agree with your decision to use intermittent fasting, just do not talk with them about it. Find support in other ways. There are many online communities devoted to this way of eating, and there are local groups in most communities that can offer you support, too.
  • Try it for a month. If you are not sure if IF is right for you, try it for at least 30 days. When you are not fasting, adopt a low-carb diet, which can help reduce your cravings. If you are not seeing the results you want or are still struggling with it after a month, decide if you are going to adjust or try something different.
  • Eating windows are not for binging. Fasting works because it restricts calories. If you eat 3,000 calories during your eating window, you will not lose weight. You need to eat a healthy diet, no matter when or how often you eat.
  • Focus on the quality of your experience. It is not about the destination; it is about the journey.
  • Exercise in moderation. Some people, especially when they are transitioning to IF, struggle with exercise. Be sure you are eating at times that are conducive to your exercise periods, to ensure you have enough energy for your workouts.

Intermittent fasting works well when it is intermittent. You cannot fast all the time. You must be flexible with your eating and make it a part of your routine. It should not become a source of stress in your life. If it is, then it is time to move on.

Precautions and Side Effects

IF is not for everyone. Those with a history of disordered eating or who are underweight should not be using intermittent fasting. If you think this may be right for you, you should discuss it with your doctor or eating counselor first. Fasting is a form of controlled eating, which can lead to or worsen eating disorders in some people.

Women may not enjoy all the same benefits from IF as men. Some women may struggle more to lose weight or improve insulin sensitivity than men. For some, menstrual irregularity is a side effect of fasting. If you have concerns about your fasting results or side effects, you should discuss them with your doctor.

Intermittent fasting is meant to be practiced part of the time. That means you should still be eating throughout the day or week. You will not enjoy the best results if your fast is too often or too long.

If you are not getting enough sleep due to a physiological problem, you may have trouble with fasting. Those who over-exercise will also likely struggle with this way of eating.

Do not take supplements or medications that dull the appetite to sustain fasting windows. If you cannot make it through a fast without support, then the fast is too long for your body.

If you notice that you become obsessed with or consumed by eating during your eating periods, you should stop using IF. Intermittent fasting is also not a way to help compensate for making poor food choices the rest of the time.

Pay attention to how your body responds to fasting. You should stop fasting if you notice dramatic changes in your sleep quality, your energy levels, your emotional health, your hormonal levels, or your appearance. All of these are signs that IF may not be the right choice for you.

Side Effects

Most people experience hunger while fasting, which is normal. In the beginning, you may also feel weak and experience brain fog. These symptoms should lessen as you adjust to fasting.

If you have a medical condition of any kind, you should talk with your doctor before trying IF. This is especially important if you have diabetes, struggle with blood sugar regulation, or have low blood pressure. Certain medications may not respond well to fasting.

If you are trying to conceive, are pregnant, or are breastfeeding, you should avoid fasting.

Final Thoughts

Intermittent fasting is not a diet but instead is a schedule of when to eat. The benefits of fasting have been recognized for thousands of years, as it was often practiced in conjunction with religious rites because it provides clarity to the mind.

Many people today enjoy fasting as a way to enhance weight loss. In addition to helping burn fat and decrease your weight, intermittent fasting can also provide you with other health benefits. These include better heart health, improved hormonal regulation, enhanced brain function, and less stress.

There is no one “right” way to fast. Each person must find the fasting window that works best for their needs. The most popular method is the 16:8 ratio, which allows you to eat for up to eight hours each day. Others find that a longer window of fasting works best for them, while still others choose to fast on some days but eat normally on others.

What is most important about IF is that you find a method that works for you and you pay attention to your body’s needs, whether you are fasting or eating. Eating more nutrient-dense foods that are lower in calories will provide your body with the nutrition it needs while still helping you lose weight.