While most diets focus on cutting calories, intermittent fasting (IF) takes a different approach. It’s all about when you eat, not just what you eat 1.
Though IF only gained popularity in 2012, it has quickly become a go-to method for managing weight, encouraging weight loss, and even addressing certain health conditions.
But what makes it appealing? It’s relatively easy to follow, low-cost and comes in different varieties to suit various lifestyles.
With its growing popularity, many people are now quite familiar with IF but may not realise there are different types or how it helps burn fat and prevent health issues. Most are only aware of the 16/8 technique, but there’s much more to it.
That’s why we’re here to give you the full breakdown of IF. We’ll explain what it really is, discuss the methods, and help you decide if it’s right for you.
What is intermittent fasting?
In the past, our ancestors ate when they were hungry or when food was available. Today, we’re programmed to eat three meals a day, hungry or not. Intermittent fasting (IF) takes us back to those traditional eating patterns.
IF is simple: you eat, then you don’t eat for a while. Your daily calorie intake might stay the same, but you spread it over a shorter time. For example, you might have breakfast and then wait 16 hours before your next meal.
This approach mimics how our bodies naturally deal with food scarcity. It’s a way of eating that aligns with our biological rhythms, offering health benefits beyond just weight management.
The Stages of IF
Intermittent fasting has different phases that show how your body enters fasting mode. These phases affect how you feel and what happens in your stomach and internal organs.
0–2 hours after eating:
Your body starts digesting your meal, causing your blood sugar to rise. You’ll feel normal as your body breaks down glycogen for energy. Your pancreas releases insulin to process glucose for immediate use and store the excess for later.
2–5 hours after eating:
Your blood sugar begins to fall as the initial spike from your meal subsides. The insulin released earlier continues working, helping your cells absorb glucose from your bloodstream. You might start to feel a slight dip in energy as your body transitions from using the immediate fuel from your meal to tapping into stored energy.
5 to 8 hours later:
Your blood sugar returns to normal. You might start feeling hungry as your stomach reminds you that it’s been a while since your last meal. However, you’re not actually that hungry.
You may also feel starving, but don’t worry; you’re fine. Your body is just used to eating at this time. Not eating now will reduce your glycogen reserve and help you lose some body fat.
Your body continues digesting food and starts using stored glucose for energy, working as if you’ll eat again soon.
Switching to Fasting Mode (8 to 10 hours later):
About 8 hours after eating, your liver uses up the last glucose reserves. Your body then enters a state called gluconeogenesis, which means it’s switched to fasting mode.
Studies show that during gluconeogenesis, your body generates glucose from body fat instead of carbohydrates. This increases your calorie burning.
This process shows how your body adapts to fasting, shifting from using stored energy to burning fat for fuel.
Turning into Fat Burning (10 to 12 hours later):
At this point, you’re running out of glycogen. You may become irritable or hungry. But stay calm, take a deep breath, and maybe drink some water. This is a sign that your body is starting to burn fat.
With little glycogen left, fat cells release fat into your bloodstream. This fat goes straight to your liver and is converted into energy for your body. Essentially, you’re tricking your body into burning fat for survival.
The Ketosis State (12 to 18 hours):
This is a metabolic state where your body fat becomes fuel for energy. The glycogen is almost used up, so your liver converts fat into ketone bodies, an alternative energy source for your body.
Fat reserves are readily released and consumed. That’s why ketosis is often called the body’s fat-burning mode. It produces fewer inflammatory by-products, offering health benefits to your heart, metabolism, and brain.
Fat Burning Mode Starts (18–24 hours):
The longer you fast, the deeper into ketosis you’ll go. By 18 hours, your body has fully switched to fat-burning mode. Research shows that after fasting for about 12 to 24 hours, energy supply from fat increases by 60%, with a significant jump at 18 hours.
Autophagy starts (24 to 48 hours):
Your body starts a process called autophagy. During this time, your cells clean out and recycle old or damaged parts. This helps keep your cells healthy and functioning properly.
During autophagy, your cells break down viruses, bacteria, and damaged components. This process provides energy to make new cell parts. It’s great for cell health, renewal, and survival. The main benefit of autophagy is that it helps turn back the clock, creating younger, healthier cells.
Growth Hormone Rises (48–56 hours):
After 48 hours of fasting, your growth hormone level is much higher than before. This increase is due to the production of ketone bodies and the secretion of hunger hormones during fasting. Growth hormone helps increase lean muscle mass and improve cardiovascular health.
Increased Insulin Sensitivity (56–72 hours):
After fasting for 2 to 3 days, your insulin level is at its lowest. This makes you more insulin-sensitive, which is beneficial, especially if you have a high risk of developing diabetes. It can also help activate autophagy (cell regeneration) and reduce inflammation.
Immune Cell Regeneration (72 hours):
Your body now turns down cellular recycling pathways and recycles immune cells damaged while fighting viruses, bacteria, and germs. It then regenerates new immune cells, making your immune system stronger.
Important note: If you feel uncomfortable at any point, stop fasting immediately and consult your doctor. Also, if you’re taking any medication, consult your healthcare professional before fasting.
The Benefits of Intermittent Fasting
There are several ways that IF can benefit you aside from weight loss, and they include:
- It can increase your physical endurance.
- IF helps maintain muscle while you lose fat.
- It may help reverse insulin resistance in type 2 diabetes.
- Fasting boosts your body’s natural cell-repair processes.
- Fasting can boost your brain function, improving memory and thinking skills.
- IF can improve heart health by lowering blood pressure and reducing strain on the heart.
Different Methods of IF
Here are the common methods of intermittent fasting:
The 16:8 Method
This method involves an 8-hour eating window and 16 hours of fasting. For example, you might eat between 11 a.m. and 7 p.m. During the remaining 16 hours (from 7 PM to 11 AM the next day), you fast, consuming only water or tea. This cycle repeats daily.
Read more: 16/8 IF method reviewed
The Eat-Stop-Eat Method
As the name suggests, you eat normally for 5 days a week and fast for 24 hours on 2 non-consecutive days. On fasting days, you have just one meal.
The 5:2 Diet
Similar to Eat-Stop-Eat, but instead of skipping meals, you reduce calories. Eat normally for 5 days, then consume only 500–600 calories on each of the other 2 days.
The Warrior Diet
This involves 20 hours of undereating, followed by 4 hours of overeating. Be cautious with this method, as it may lead to disordered eating habits like binge eating for some people 2.
The OMAD (One Meal A Day) Diet
In this approach, you fast for 23 hours and have a single 1-hour eating window each day. It’s a more extreme form of intermittent fasting.
Note that each method has its pros and cons, so before starting any of the methods, check out their critical reviews.
Prep yourself with: Debunking 10 Popular Diet Myths for a Healthier You
Symptoms during fasting
Intermittent fasting can seem tough for a beginner. That’s why it’s smart to start with the easiest level and gradually increase the difficulty as you get used to it.
While fasting, you might feel a bit tired, hungry, or irritable—that’s normal. But you should never feel truly unwell. Pay attention to your body, especially if you’re new to fasting.
Everyone is different, so if the routine feels too challenging, don’t hesitate to adjust it. Make it easier or tweak it to fit your needs.
However, if you become extremely tired, weak, sick, or experience unusual discomfort, stop fasting right away and talk to a doctor. Your health comes first.
Should I start IF?
Yes, you should definitely give IF a try and see if this method of weight loss is effective for you. Start by experimenting and observing how your body responds. Pay attention to its effects on your weight, daily activities, and mental well-being. Business Insider reports that while IF can aid weight loss and offer health benefits, it is not suitable for everyone.
When starting IF:
- Begin with shorter fasting periods.
- Stay hydrated during fasting periods.
- Find the fasting method that fits your lifestyle.
- Engage in activities that distract you from hunger and prevent boredom.
- Avoid binge eating during your eating window, especially unhealthy foods.
- Stop immediately if you feel ill or if it significantly impacts your daily activities.
Remember, everyone’s experience with IF is unique. It’s essential to research the dos and don’ts of fasting diets before beginning. Listen to your body and speak with a healthcare professional if you have any concerns. IF can be an effective tool for some, but it’s important to approach it mindfully and safely.
Conclusion
Intermittent fasting works for many people, but not for everyone. Research shows it can help with weight loss, lower cholesterol, and improve cell health. If you’re interested, give it a try, but don’t push yourself too hard.
Most importantly, if you have health issues, talk to your doctor first. Fasting can be very effective, but it needs to be done carefully. Your health comes first, so listen to your body as you try this fast.
REFERENCES
Hennessy, N. (2023). What Is Intermittent fasting? (online) www.bupa.co.uk. Available at: https://www.bupa.co.uk/newsroom/ourviews/intermittent-fasting (Accessed July 26, 2024).
Johns Hopkins Medicine (2021). Intermittent fasting: What Is it, and How Does It work? (online) Johns Hopkins Medicine. Available at: https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work (Accessed July 26, 2024).
Kubala, J. (2018). The Warrior Diet: Review and Beginner’s Guide. (online) Healthline. Available at: https://www.healthline.com/nutrition/warrior-diet-guide (Accessed July 26, 2024).
Lifesum (2023). Optimize Your Body and Mind: Unlocking the Stages of Intermittent Fasting. (online) lifesum.com. Available at: https://lifesum.com/nutrition-explained/optimize-your-body-and-mind-unlocking-the-stages-of-intermittent-fasting (Accessed July 26, 2024).
Reck, T. (2020). Does the Eat Stop Eat Diet Help to Lose Weight? (online) Simple.life Blog. Available at: https://simple.life/blog/eat-stop-eat-plan/ (Accessed July 26, 2024).
