Intermittent Fasting — The Complete Beginner’s Guide
Intermittent fasting is a pattern of eating that involves not always having to eat food, but abstaining from it. It means periods of time when you do eat food, and other times when you don’t eat any food, and you give your gut a break.
Intermittent fasting (IF) is more than just a popular trend in the health and fitness world—it’s an eating pattern that dates back to the origins of human evolution. Unlike traditional diets that focus on what you eat, intermittent fasting centres around when you eat.
By cycling between periods of fasting and eating, IF allows your body to tap into its natural ability to function optimally without constant food intake. Common methods include the 16-8 method, fasting for 16 hours and eating during an 8-hour window, or even engaging in 24-hour fasts twice a week. Many people adopt IF for weight loss, and it can be highly effective when correctly performed.
If you want to know the 6 best ways to perform intermittent fasting, you may be interested in the following article: 6 Best Ways of Intermittent Fasting
There are various ways to incorporate intermittent fasting into your routine, and many approaches are gaining popularity. This blog post will break down everything you need to know, including the basics, and how fasting benefits your gut and metabolism, and the potential risks.
Intermittent Fasting And Periodic Fasting
The two main ways many people fast are called intermittent fasting, and periodic fasting. I’ll be focusing on intermittent fasting, because it is such a widely used and effective tool when it comes to improving your digestive health, recovering after an illness, losing weight, reducing blood pressure, reversing diabetes, and much more.
Both intermittent fasting and periodic fasting involve going without food for short amounts of time and then eating again, but they are not the same in terms of when to stop eating and how long for. Intermittent fasting means you fast on a recurring basis, whereas periodic fasting tends be more sporadic, but often includes longer periods of time fasting. Periodic fasting refers to with periods of fasting lasting from 2 to as many as 21 days.
Fasting Is An Ancient Concept
Fasting, practiced for thousands of years, has been recognised for its healing properties by ancient cultures, including Greek and Indian physicians.
Hippocrates (400 BC) recommended fasting to treat various ailments, and found it could help those with epilepsy (by inducing a state of ketosis). (Dingledine 2016).
Fasting has long been a practice not only for health reasons but also for religious and spiritual purposes. Religious fasting is practiced by people of all faiths, including Christianity, Islam, Buddhism, Jainism, as well as Hinduism, Judaism, and Taoism. Studies have found fasting can offer benefits at many levels, from individuals to entire communities (Trabelsi et al., 2022).
Historically, humans didn’t have the luxury of three meals a day and evolved in environments where food scarcity was common. This led to adaptations allowing us to thrive both physically and cognitively during times of food deprivation (Mattson 2017)
Today, fasting makes a lot of sense. All too many of us overeat, often resulting in metabolic issues like insulin resistance, excess body fat, and high blood pressure, especially when combined with a sedentary lifestyle.
Embracing intermittent fasting is a way to break these patterns, giving your gut the much-needed break it deserves and reconnecting with the natural rhythms of your body. The latest research shows that brief periods of fasting can help reduce weight and improve metabolic health, but it goes beyond that—it can also have a positive effect on our gut health as we shall learn later on this page.
Imagine writing a book about fasting over a hundred years ago in an age when such thoughts were considered “bad health advice” bordering on quackery. Sinclair is remembered for the quote: “It is difficult to get a man to understand something, when his salary depends upon his not understanding it.”
We Function At A Higher Level in a Food Deprived State
Fasting periodically allows us to truly experience what it feels like to have an empty stomach, along with the subtle sensations that come as our gut empties. Once you get used to it, this can be a surprisingly refreshing and rewarding experience. You’ll feel lighter, more energetic, and, as research shows, better in many ways. I highly recommend it for anyone looking to reset their body and mind.
Historically, humans evolved in environments where food was scarce, so our bodies developed adaptations that allowed us to function optimally, both physically and mentally, even in the absence of food. Fasting taps into this natural ability, helping to support better health and cognitive performance (Mattson 2017).
Upton Sinclair
“I have found good health, indeed perfect health; a new state of being, a potentiality of life; a sense of lightness and cleanness and joyfulness, such as I did not know could exist in the human body.” Upton Sinclair, The Fasting Cure – 1911
Recognise The Difference Between Hunger and Food Cravings
It’s easy to agree that eating everything on the table every day would lead to serious health issues long before we even reach adulthood. Learning to control our appetite is essential if we want to maintain a healthy weight and avoid obesity over the course of our lives. The key question we often ask ourselves, consciously or not, is, “Should I eat now, or should I wait until later?”
Weight gain is a result of consistently consuming more energy than we burn, leading to excess body fat. In my years as a naturopath, I never considered reducing food intake at certain times as “fasting”—it simply seemed like common sense. Maintaining both health and weight means keeping a close eye on your food choices, especially as you age. One of the most important lessons is recognising the difference between true hunger and cravings.
This understanding forms the foundation of intermittent fasting. When you think of fasting as a mindful practice—listening to your body and exercising patience with food choices—it becomes much easier to grasp.
Fasting works best when it’s part of a balanced lifestyle, where you eat consciously and stay attuned to your body’s needs. One researcher found emotional eating is a behavioural mechanism that drives development of abdominal obesity. (Konttinen 2019)
Sleep also plays a crucial role in controlling appetite, cravings, and eating behaviours. Poor sleep patterns can trigger unhealthy snacking and lead to weight gain.
Research shows that even modest sleep reduction—about one-third less than normal—can increase hunger, food cravings, and portion sizes, which can eventually lead to overeating and weight gain (Yang 2019). Maintaining good sleep hygiene is essential to avoid these pitfalls and support a healthier approach to eating.
Paul Bragg
“Fasting clears away the thousand little things which quickly accumulate and clutter the body, mind and heart. It cuts through corrosion and renews our contract with God and Mother Earth.” Paul Bragg, The Miracle of Fasting – 1972
Fasting Controls Appetite and Weight
While fasting is far from a new concept, it became popular again in the 20th century for treating conditions like obesity, diabetes, and epilepsy. Long before it became trendy, fasting was known for its benefits, and today we see even more evidence supporting it.
The ketogenic diet, developed as an alternative to fasting, eventually became widely used, particularly for weight loss. However, its original purpose was to manage epilepsy, until anti-convulsant medications reduced the need for it (Wheless 2008).
Despite its long history, fasting still remains a debated topic. Supporters argue it helps with weight loss, insulin regulation, lower triglycerides, and slowing down the aging process.
Others, including some dieticians and nutritionists, claim it can lead to nutrient deficiencies, cravings, and even binge eating, leading to weight gain.
Understanding the balance between the science and philosophy of eating can help navigate these differing viewpoints. Most patients I’ve worked with in the clinic over the years who discovered fasting found it incredibly beneficial, both mentally as well as physically.
Intermittent Fasting Is An Effective Way to Manage Body Weight
Intermittent fasting (IF) has gained traction as a popular method for weight loss and overall body weight management. Once you experience its benefits, not just in terms of shedding pounds but also in maintaining a healthy weight, you’ll likely be hesitant to return to old eating habits.
Over the years, I’ve had countless discussions with patients who struggled to lose weight, only to find that it creeps back up. Fasting has proven to be a powerful, often overlooked tool for keeping weight off long-term. It works by helping you reduce snack cravings, control portion sizes, and reshape your eating habits. Moreover, fasting can positively impact your gut bacteria and even extend lifespan. Studies consistently show that eating less, particularly as we age, is a key to living a longer, healthier life.
Research supports the idea that long-term and periodic calorie reduction can boost overall health. Calorie restriction doesn’t mean starving yourself; it means eating fewer calories while ensuring you get all necessary nutrients. Fasting for specific periods gives your body time to repair and regenerate.(Mitchell et al., 2019)
Types of Intermittent Fasting
Two of the most researched methods include:
Studies have shown that time-restricted eating can lead to mild weight loss (1-4%) (Chow 2020), while alternate-day fasting can result in slightly more (3-6%) weight loss over several months (De Cabo 2019).
Article Of Interest: 6 Best Ways of Intermittent Fasting
Caution With Fasting If You Have A Medical Condition
If you have a medical condition like diabetes, heart disease, or cancer, it’s important to consult your doctor before starting any fasting regimen. While fasting can offer many benefits, certain health issues require extra caution. However, if you have conditions like Candida yeast infections, SIBO, IBS, or IBD, fasting is often still beneficial and can help improve your symptoms.
In my experience, most patients who’ve tried fasting have reported positive outcomes. Many lost weight, felt more energetic, and experienced an overall boost in well-being. It’s a simple, cost-free way to improve your health.
By combining fasting with healthy eating and regular physical activity, you can steadily lose weight while building great gut health. Losing 1-2 pounds (0.5–1 kg) per week is a safe, proven method for long-term success. This balanced approach is, in my opinion, the most effective for both gut health and weight management.
Intermittent Fasting Isn’t Just About Weight Loss
Fasting isn’t just about losing weight—it can improve your gut health by fostering a more balanced microbiome. Some of my patients find fasting much easier than strict calorie counting. In fact, IF can improve your health even without significant weight loss (Sutton 2018). It’s more about eating healthier, not necessarily eating less.
However, if your diet is filled with ultra-processed foods (UPFs) like sugary drinks, chips, and other high-calorie snacks, fasting will be more challenging. Removing these foods from your diet first will make fasting easier and more effective in the long run.
Intermittent Fasting Is Best Done On A Schedule
For intermittent fasting to be truly effective, it can’t be done at random—it needs to follow a consistent schedule, much like a well-structured exercise program. Regularity is key for success, as most healthy individuals already tend to eat at fairly predictable times. By maintaining this consistency, you give your body time to adjust to periods of fasting and feeding, maximizing the benefits.
Everyone’s experience with intermittent fasting will vary, which is why different fasting methods may work better for some than for others. I’ll guide you through several approaches, so you can find the one that suits you best. Studies consistently support the effectiveness of intermittent fasting for weight loss and overall well-being.
For example, in a 6-month study involving 107 overweight or obese men and women, 32% of participants reported reduced depression, improved mood, and increased self-confidence through intermittent fasting (Harvie 2011).
Moreover, an analysis of 27 clinical trials found that intermittent fasting led to weight loss ranging from 0.8% to 13% of baseline body weight, regardless of changes in calorie intake. Participants’ BMI dropped by an average of 4.3% in studies lasting between 2 weeks and 3 months. Notably, no adverse effects were reported (Welton 2020).
Benefits of Intermittent Fasting Supported by Research
Autophagy
Autophagy, which translates to “self-eating,” is a natural process in which the body cleans out damaged or dysfunctional cells, essentially rejuvenating itself. Though it may sound destructive, it is quite the opposite—it’s the body’s way of getting rid of harmful material and maintaining cellular health.
During autophagy, the body either breaks down damaged molecules completely or recycles them into new, usable components for cellular repair. This process is essential for maintaining overall health and is one of the many benefits linked to intermittent fasting.
An increasing number of comprehensive studies are discovering that intermittent fasting is essentially a cleansing exercise when it comes to our health.
Autophagy takes place during fasting, which lasts more than 16 hours, it provides our body’s cell with a source of energy and building blocks to create new components. Autophagy is most important during any time of cell stress, such as nutrient deprivation, any kind of infection, or other forms of damage like oxidative stress. Aman 2021)
The author of a recent study concludes that intermittent fasting has a role in the upregulation of autophagy, with sufficient evidence overwhelmingly suggesting that autophagy is induced in a wide variety of tissues and organs in response to food deprivation. (Bagherniya 2018)
Longevity
Your lifespan will increase when you fast regularly. Research has shown that fasting can increase the body’s resistance to many age-related diseases and extend the lifespan of various animals. (Rose 2018)
Better Metabolic Health
Eating too many calories (too much food) is frequent in the Western world, and has been linked to systemic low-grade chronic inflammation. (Lumeng and Saltiel 2011) Studies suggest that intermittent fasting may reduce markers of inflammation associated with various chronic diseases. (Jordan 2019) Intermittent fasting has also been linked to improving a person’s insulin sensitivity, leading to a reduction in the risk of developing diabetes. (Altay 2022)
Improved Gut Health
Intermittent fasting offers remarkable benefits for our gut health, with emerging studies showing a significant impact on the gut microbiome. Research indicates that intermittent fasting can enhance the diversity of gut bacteria, which is essential for maintaining a healthy digestive system.
One notable finding involves a specific family of anaerobic bacteria called Lachnospiraceae, which flourishes during fasting periods. This bacteria plays a key role in producing butyrate, a short-chain fatty acid (SFCA) that supports metabolism and can even help slow the aging process (Larrick 2021).
In addition, intermittent fasting has been shown to give gut bacteria time to rest and repopulate, further promoting gut health. These positive effects on the microbiome contribute to the metabolic and longevity benefits of fasting (Teker 2022).
Weight Loss and Weight Maintenance
In 27 different clinical trials examined, intermittent fasting resulted in weight loss, ranging from 0.8% to 13.0% of baseline body weight. Weight loss occurred regardless of changes in overall caloric intake, an symptoms such as hunger remained stable or even decreased, and no adverse events were reported. (Welton 2020). Based on 3 separate studies, fasting on alternate days resulted in weight loss as well as reductions in blood glucose and insulin concentrations. (Patterson 2015)
Better Brain Health
While clinical research regarding intermittent fasting and brain function is still in its infancy, animal studies clearly demonstrate different pathways by which fasting has beneficial impacts on brain-related disease. In healthy people, while fasting has no immediate benefits for cognition function; but there are signs that it may guard against the development of several neurological diseases. (Gudden 2021)
A study published only last year suggests that intermittent fasting induces in the central nervous system (the brain) different neuronal adaptations, including cellular stress resistance, synaptic plasticity (the ability of nerve cells to modify their connections, involved in brain network remodelling following different types of brain damage), as well as the growth and development of nerve cells and tissue.
Intermittent fasting helps boost the production of BDNF (Brain-Derived Neurotrophic Factor) and BHB (Beta-hydroxybutyrate, a principle ketone body ), both associated with improved brain function and mood regulation. (Brocchi 2022)
Cancer Prevention
Chronic caloric restriction has been shown to have powerful anti-cancer actions in both preclinical and clinical studies but may be difficult to sustain. As an alternative to restricting calories, there has been growing interest in intermittent fasting as a result of promising study results. (Clifton 2021) Periodic fasting has consistently show powerful anticancer effects in mouse cancer studies including the ability to potentiate chemo-radiotherapy and to even trigger anticancer immunity. (Nencioni 2019)
Healthy Heart
The exact mechanism underlying the observed benefits of intermittent fasting on several cardiovascular risk factors, such as obesity, high blood pressure, high cholesterol levels, and diabetes, are yet to be fully understood. Moreover, following a cardiac incident, intermittent fasting has been linked to better results. (Dong 2020)
Benefit from the use of intermittent fasting have been confirmed in research on the development of plaque inside the body’s arteries. Intermittent fasting inhibits the development of atherosclerotic plaque by reducing the concentration of inflammatory markers, such as IL-6 (Interleukin-6), homocysteine, and C-Reactive Protein (CRP). (Malinowski 2019)
Improved Sleep
While older studies were inconclusive, a more recent study involving 99 female participants found many who reported improved sleep quality patterns with time-restricted fasting pattern, independent from weight loss. (Kesztyüs 2020)
Intermittent Fasting Is Easy To Follow, Safe, and Well-Tolerated
Research has found intermittent fasting simple and convenient to follow that does not require any complicated meal planning, calorie counting, or special foods.
It is also safe, The results from a study involving 1422 participants showed that periodic fasting is safe and well tolerated. It led to enhancement of emotional and physical well-being and improvements in relevant cardiovascular and general risk factors, as well as several subjective health complaints. (de Toledo 2019).
The 10 Best Intermittent Fasting Concepts
It’s not easy sometimes being true to ourselves, it’s important to separate ourselves from the crowd and choose to be different if we want to make a difference in our lives. It’s entirely possible and achievable for us to be healthy, lean, and strong without being silly about what we eat, in my opinion.These concepts can help with your fast, I’ll list them then explain each one:
1. We Can Choose When and What we Eat
While it’s important to make food choices that suits us, when it comes to intermittent fasting, we are best to focus on an important decision we make several times a day, i.e.: should we eat something or not? Don’t worry about someone else, whether they are eating or not is beside the point, maybe they’re hungry, or they’ve consumed a meal or snack some time ago.
Just because somebody else is eating, it doesn’t mean we need to eat, and if we do eat when somebody else is eating, we don’t need to eat the same amount or even more. We need to choose when and what to eat, a most basic principle. Research has found strong evidence that people tend to eat more food when eating with friends and family, relative to when eating alone.
This is known as the ‘social facilitation of eating’, and especially relates to high-energy foods (take-away and ultra-processed food). (Ruddock 2021)
2. We Don’t Have To Eat If We Feel Stressed
It is best not to eat if we are stressed or emotional, because the digestive process won’t work too well under these conditions.
During human evolution, food was scarce and life-threatening stressors were frequent; studies have found however, in our current obesogenic environment where food is plentiful, highly palatable and easy accessible, the proliferation of different stressors can help drive eating (cravings) without any real metabolic need. (Yau 2013)
3. We Don’t Need To Eat Three Meals Every Day
Some of us believe we all need to eat three meals every day. This may sound strange, but just accepting the idea we don’t have to eat all the time and can choose when we eat is enough to set us apart from how most people think about food.
The origin of the belief that eating three meals per day is the best when it comes to health is a mix of cultural heritage and early studies. (Paoli 2019) Much current research into intermittent fasting and health has found this not to be true however.
4. We Don’t Have to Eat if We Don’t Feel Hungry!
Hunger training (HT), is a way to teach people to eat when they are hungry by making the link between hunger signs and their blood-sugar (glucose) levels.
When commitment is high, HT is one of the best ways for changing the way we eat and losing weight. (Bruin 2019)
5. Digestive Rumbling is Good and Not a “Bad” Sign
We’ve all heard our stomach rumbling, growling, or gurgling—these are all sounds we’ve probably heard before. In most cases, it’s nothing more than a sign of hunger and our body’s way of telling us it’s time to eat. The contractions of muscles that produce rumbling noises in our stomach and intestines don’t only occur when we are hungry; they occur in fact most of the time.
But when our gut is empty, these noises are easier to hear because air is the only substance assisting in their movement. Our stomach releases a hormone called ghrelin a few hours after our last meal, alerting our brain to hunger and initiating the process of peristalsis (gut contractions) again. This serves as a kind of “internal housekeeping” for our body, clearing our stomach of any leftover food or liquids and sending them down the digestive tract and into the intestines.
It also prompts our body to think about when it will have its next meal. Therefore, it’s not always necessary to eat while our stomach is growling. It can only indicate that the food we just ate travelled has farther along our digestive tract.
6. Not Falling Into the Same Snacking Habits as Before
We need to be cautious of not going back to old snacking habits. As soon as we stray even a little from what’s right, momentum builds, and the danger is always there we quickly return to our old habits. One area where intermittent fasting can be very helpful is this one.
When bad habits start to creep back into our lives, a break from eating can help us “reset.” A recent study found the higher the strength of habit to snack between meals, the higher the amount of energy intake (sugar and fat) from snacks. The association between habit strength and highly-processed food intake from snacks was moderated by a person’s education level. (Wouters 2018)
7. We Can Skip Meals on Fasting Days if We Feel Like It
Skipping meals haphazardly on fasting and non-fasting days is not the best idea. If we believe going without meals is a wise strategy for keeping off weight and staying healthy, think again.
Although our calorie intake will decrease, there’s a big possibility that we may give in to our cravings and overindulge in ultra-processed unhealthy meals. I’ve seen this result in a hazardous cycle of yo-yo dieting for many patients over the years.
Our resting metabolism, the process by which our body burns calories, can be disrupted by yo-yo dieting. Due to the unpredictability of our meal times, our body will store fat and not burn calories as effectively. Missing meals at random times, often due to a stressful lifestyle, might also have a negative effect on our hunger hormones.
It’s possible that our body produces less leptin, the hormone that suppresses appetite and makes it more difficult for us to recognise when we’re satisfied. Skipping breakfast to lose weight isn’t the best idea, evidence from observational studies indicates that in real-world settings, breakfast skipping can lead to weight gain and the onset of overweight and obesity. (Wicherski 2021)
8. Know the Difference Between Cravings and Hunger
Know the difference between cravings and being hungry is very important if we want to maintain good health in the long-term.
Unlike hunger signals, cravings are subject to fluctuate over time and are typically brought on by feelings like stress, boredom, anxiety, or depression, a connection to or a fondness for a particular cuisine, or being in close proximity to appetising food. In contrast to hunger, which can be remedied by any food, a craving can only be satisfied by one particular food or drink item.
9. For Longevity Sake it is Better to Eat Less Rather Than More
Aging is the highest risk factor for many human diseases, including cancer, dementia, diabetes and metabolic syndrome. Caloric restriction has been shown in animal models to be one of the most effective interventions against these age-related diseases. (López-Lluch 2016)
10. Eating Less Food is Healthier For Our Gut Than More
It’s important to eat mainly nourishing and healthy foods, and by doing so, we’ll be reducing the poorer food choices automatically. Instead of solely reducing the amount of food we consume, focus on the quality of the food. A diet rich in fibre, whole grains, fruits, vegetables, and fermented foods can promote a healthy and diverse microbiome.
Reducig processed foods, added sugars, and saturated fats will reduce our total calorie intake in general. Intermittent fasting benefits gut bacteria because it gives them time for rest and to repopulate. (Ahsan 2023)
Eric Bakker N.D.
Greetings! I am a naturopathic physician from New Zealand. Although I’ve retired from clinical practice since 2019, I remain passionate about helping people improve their lives. You’ll find I’m active online with a focus on natural health and wellbeing education through my Facebook page and YouTube channel, including this website.
