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  • Josie Barnes

How Does Intermittent Fasting Work For Effective Weight Loss

Intermittent Fasting

In this blog post, we're going to dive more into intermittent fasting and how it can help for long term fat loss and weight management. By eating fewer calories and using time-restricted eating, the weight often 'falls off' for lots of people. It's not for everyone, but if you are interested in intermittent fasting, this blog post will answer your questions. We will cover: Intermittent Fasting Alternate-Day Fasting The Eight-Hour Window Frequently Asked Questions about Intermittent Fasting In our FAQ about intermittent fasting, there are also some ideas on dishes that you should be eating when you are 'allowed' to eat. --

A clock showing when you can eat and when you should fast
Intermittent Fasting Explained

Intermittent fasting (IF) has emerged as a popular dietary strategy, gaining widespread attention for its potential to promote weight loss, enhance metabolic health, and improve overall well-being. Unlike traditional calorie-restricted diets, IF focuses on cycling between periods of eating and fasting, creating a metabolic shift that supports weight management efforts.

Understanding the Physiology of Intermittent Fasting

During fasting periods, the body transitions from using glucose, its primary energy source derived from food, to utilising stored energy reserves, primarily fat. This metabolic switch, known as ketosis, occurs when glycogen stores deplete, prompting the liver to break down fat into ketones, alternative energy molecules that fuel the body during fasting intervals.

Intermittent Fasting Methods: A Spectrum of Approaches

IF encompasses various methods, each with distinct fasting and eating windows. The most common IF approaches include:

  1. 16/8 Method: This involves fasting for 16 hours each day and restricting eating to an 8-hour window, typically between 12 pm and 8 pm.

  2. 5:2 Diet: This method entails eating normally for five days and restricting calorie intake to 500-600 calories on two non-consecutive days.

  3. Eat-Stop-Eat: This involves fasting for a full 24 hours once or twice a week.

  4. One Meal a Day (OMAD): This approach involves consuming one meal per day, typically within a specific window.

Scientific Evidence Supporting Intermittent Fasting

Numerous studies have investigated the effectiveness of IF for weight loss. A 2019 review of 30 studies concluded that IF resulted in significant weight loss compared to traditional calorie restriction diets. Additionally, IF has been shown to:

  1. Reduce abdominal fat: IF has been associated with a decrease in visceral fat, a type of fat linked to various health risks.

  2. Improve insulin sensitivity: IF can enhance insulin sensitivity, a crucial factor in regulating blood sugar levels and reducing the risk of diabetes.

  3. Promote heart health: IF may positively impact heart health by lowering LDL (bad) cholesterol and triglycerides while increasing HDL (good) cholesterol levels. Losing weight is great for preventing heart disease in general.

  4. Reduce inflammation: IF has been shown to reduce inflammation, a chronic condition associated with various health problems.

Considerations for Implementing Intermittent Fasting

While IF offers potential benefits, it's essential to consider individual factors before embarking on this dietary strategy.

  1. Consult a Healthcare Professional: Individuals with underlying health conditions, such as diabetes or pregnancy, should consult a healthcare professional before starting IF.

  2. Gradual Implementation: Initiating IF gradually allows the body to adapt to the new eating pattern.

  3. Hydration and Nutrient-Dense Eating: Proper hydration is crucial during fasting periods. During eating windows, focus on nutrient-dense foods to support overall health.

  4. Listen to Your Body: Pay attention to the body's signals and adjust fasting windows accordingly.

  5. Seek Support: Consider joining an IF community or seeking guidance from a registered dietitian for personalised support.


Fasting days: Fasting days in intermittent fasting (IF) are periods of time when you abstain from consuming any calories. The length of fasting days can vary depending on the type of IF you are following. For example, the 16/8 method involves fasting for 16 hours each day, while the Eat-Stop-Eat method involves fasting for a full 24 hours once or twice a week.

During fasting days, your body enters a state called ketosis. This is when your body starts to break down stored fat into ketones for energy. Ketones can be an effective source of energy, and they may also help to suppress appetite.

There are several potential benefits to fasting days, including:

  • Weight loss: Fasting days can help you to create a calorie deficit, which is necessary for weight loss. It's also great to help control blood pressure as part of an overall healthy diet.

  • Improved insulin sensitivity: Fasting days can help to improve insulin sensitivity, which is important for regulating blood sugar levels.

  • Reduced inflammation: Fasting days may help to reduce inflammation, which is a chronic condition that is linked to many diseases.

  • Improved brain function: Fasting days may help to improve brain function by increasing the production of a protein called brain-derived neurotrophic factor (BDNF).

However, there are also some potential risks associated with fasting days, including:

  • Hunger and cravings: Fasting can cause hunger and cravings, which can be difficult to manage.

  • Fatigue: Fasting can make you feel tired and sluggish.

  • Digestive problems: Fasting can cause digestive problems, such as constipation and diarrhoea. It isn't suitable for people with chronic diseases such as cardiovascular disease.

If you are considering trying IF, it is important to talk to your doctor first. They can help you to determine if IF is right for you and can provide you with support and guidance.

Here are some tips for making fasting days easier:

  • Start slowly: Start by fasting for shorter periods of time and gradually increase the length of your fasts.

  • Stay hydrated: Drink plenty of water and unsweetened beverages throughout the day.

  • Choose nutrient-dense foods: When you do eat, choose nutrient-dense foods that will help you feel full and satisfied.

  • Listen to your body: If you are feeling hungry, tired, or lightheaded, break your fast and eat something.

Having an eating window (or time-restricted eating as it is sometimes know), eating fewer calories can help most people achieve a satisfactory body weight.

How Alternate-Day Fasting Works

Alternate-day fasting (ADF) is a type of intermittent fasting that involves fasting on alternate days and eating normally on non-fasting days. This method is one of the most popular and well-studied forms of IF, with research supporting its effectiveness for weight loss and overall health improvement. During fasting days, individuals consume no or very few calories, typically restricting intake to 500-600 calories. This period of fasting allows the body to use stored energy reserves, primarily fat, for fuel. Fasting windows can vary depending on individual preferences and may range from 16 to 24 hours. A recent control group of 100 people found that 95% of them felt 'overly hungry' on fasting days.

On non-fasting days, individuals can eat normally, adhering to a balanced and nutritious diet. This approach allows the body to replenish essential nutrients and maintain overall health. The next day after fast days is when you stock up on what your body needs (and is craving). Even on non-fasting days, it's good to have an eating plan so that you don't binge too much, not good for short term weight loss. Alternate day fasting is one of the fastest ways to lose weight we've seen in recent years - apparently the cavemen practised it!

Benefits of Alternate-Day Fasting

ADF offers a range of potential benefits, including:

  1. Effective Weight Loss: Numerous studies have demonstrated the effectiveness of ADF for weight loss. In a 2017 review of 12 studies, ADF was found to be as effective as traditional calorie restriction diets for weight loss.

  2. Improved Metabolic Health: ADF has been shown to improve various metabolic markers, including insulin sensitivity, blood sugar control, and lipid profiles.

  3. Reduced Inflammation: ADF may help reduce chronic inflammation, a major contributor to various health problems.

  4. Potential Anti-Aging Effects: Studies suggest that ADF may have anti-aging effects by promoting cellular repair and longevity.

The Eight-Hour Window: A Simple and Effective Approach to Weight Loss

In the realm of intermittent fasting (IF), the eight-hour window method stands out as a simple yet effective approach to weight loss. This method involves restricting food intake to an eight-hour window each day while fasting for the remaining 16 hours. The eight-hour window typically falls between 12 pm and 8 pm, allowing individuals to maintain a regular sleep-wake cycle. The eight-hour window has specific periods of fasting (mainly when you are asleep) and the amount of weight you can lose is acceptable to many people wanting to lose weight. Nutrition experts also agree that this is potentially more beneficial (and safer) than alternate day fasting.

Mechanisms of Weight Loss with the Eight-Hour Window

The effectiveness of the eight-hour window for weight loss can be attributed to several mechanisms:

  1. Reduced Calorie Intake: By limiting eating to an eight-hour window, the overall calorie intake is naturally reduced, creating a calorie deficit, which is essential for weight loss.

  2. Metabolic Shift: During fasting periods, the body transitions from burning glucose, its primary energy source derived from food, to utilizing stored energy reserves, primarily fat. This metabolic shift, known as ketosis, occurs when glycogen stores deplete, prompting the liver to break down fat into ketones, alternative energy molecules that fuel the body during fasting intervals.

  3. Hormonal Regulation: The eight-hour window can influence the body's hormone production, promoting weight loss. For instance, fasting can increase levels of growth hormone, a hormone associated with fat burning and muscle growth.

  4. Improved Insulin Sensitivity: Fasting periods can enhance insulin sensitivity, a crucial factor in regulating blood sugar levels and reducing the risk of diabetes. Improved insulin sensitivity facilitates more efficient glucose uptake by cells, preventing excess glucose storage as fat.

Benefits of the Eight-Hour Window Beyond Weight Loss

In addition to weight loss, the eight-hour window has been linked to several other health benefits, including:

  1. Reduced Inflammation: Fasting can help reduce chronic inflammation, a contributing factor to various health problems, including heart disease, cancer, and autoimmune disorders.

  2. Improved Brain Function: Fasting may promote brain health by increasing the production of brain-derived neurotrophic factor (BDNF), a protein involved in memory, learning, and neurogenesis.

  3. Enhanced Cellular Repair: Fasting may trigger cellular repair mechanisms, potentially contributing to anti-aging effects.


Frequently Asked Questions About Intermittent Fasting:

We have scrambled around the web and picked the top questions people often ask when thinking about starting intermittent fasting. There are different ways to approach weight loss, eating healthy food including whole grains is only one piece of the weight-loss jigsaw. Here are the most common questions:

What exactly is intermittent fasting?

Intermittent fasting (IF) is an eating pattern that cycles between periods of eating (eating window) and fasting - it is effective for fat loss and achieving an ideal body weight. During fasting periods, you abstain from consuming calories, while during eating periods, you can eat normally. There are several different IF methods, each with varying fasting and eating windows. Periods of fasting change depending on the type of intermittent fasting program you are on.

How does intermittent fasting work for weight loss?

IF can promote weight loss by creating a calorie deficit. When you eat fewer calories than your body burns, it taps into stored energy reserves, primarily fat, for fuel. This process is known as ketosis, and it can lead to significant weight loss over time.

What are the benefits of intermittent fasting?

In addition to weight loss, IF has been linked to several other health benefits, including:

  • Improved insulin sensitivity

  • Reduced inflammation

  • Enhanced brain function

  • Potential anti-aging effects

Is intermittent fasting safe for everyone?

IF is generally safe for healthy adults. However, it is not recommended for pregnant women, breastfeeding women, or people with certain health conditions, such as diabetes or eating disorders. It is always best to talk to your doctor before starting IF.

How often should I fast?

The frequency of fasting depends on the IF method you choose. Some popular methods include:

  • 16/8 method: Fast for 16 hours each day and eat all your meals within an 8-hour window.

  • 5:2 diet: Eat normally for five days and restrict calorie intake to 500-600 calories on two non-consecutive days.

  • Eat-Stop-Eat: Fast for a full 24 hours once or twice a week.

What should I eat when I'm not fasting?

During eating periods, it is important to focus on nutrient-dense foods that will help you feel full and satisfied. This includes lean protein, fruits, vegetables, and whole grains. We've got some more ideas below.

Can I drink anything while I'm fasting?

Yes, you can drink water, unsweetened tea, and black coffee while fasting. These beverages will not break your fast and you should be encouraged to drink them.

What are some tips for making intermittent fasting easier?

  • Start slowly: Begin with shorter fasting periods and gradually increase the duration as your body adjusts.

  • Stay hydrated: Drink plenty of water throughout the day, even during fasting periods.

  • Listen to your body: If you are feeling overly hungry, tired, or lightheaded, break your fast and eat something.

  • Find an IF method that works for you: There are many different IF methods to choose from, so experiment until you find one that fits your lifestyle.

  • Appetite suppressants may help to stop hunger.

Is intermittent fasting a sustainable way to lose weight?

Yes, IF can be a sustainable way to lose weight, especially when combined with a healthy diet and regular physical activity. However, it is important to find an IF method that you can stick with long-term.

Where can I find more information about intermittent fasting?

There are many resources available online and in libraries about intermittent fasting. You can also talk to a registered dietitian or other healthcare professional for specific advice as some people that start a 'fast diet' can experience side effects. Remember, if in doubt, speak with a GP. What alternatives are there to intermittent fasting? Intermittent fasting isn't for everyone. Many people don't like feeling hungry despite shedding their fat stores, and it isn't suitable for anyone with a health condition. You can always try weight-loss supplements, or just exercise and eat healthy foods and you are probably on the right path. There's always prescription weight loss opportunities like Saxenda, although bear in mind that you'll need to be assessed by a GP or Doctor for prescription medication.

What are some good ideas for dishes or recipes that I should be using or eating when on an intermittent fasting diet? When following an intermittent-fasting (IF) diet, it's crucial to make informed choices during your eating periods to fuel your body effectively and support your weight loss goals. Here are some suggestions for nutritious and satisfying dishes to incorporate into your IF routine:

Breakfast Options:

  1. Greek Yogurt Parfait with Berries and Granola: Layer a generous serving of Greek yogurt with a mix of fresh berries and a sprinkle of granola for a protein-rich, high-fibre breakfast.

  2. Avocado Toast with Eggs: Toast your favourite bread and top it with mashed avocado, a fried or poached egg, and a sprinkle of salt and pepper for a nutrient-dense and tasty meal.

  3. Smoothies: Blend together fruits, vegetables, protein powder, and yogurt to create a quick, filling, and on-the-go breakfast option.

  4. Oatmeal with Nuts and Seeds: Cook oatmeal with your choice of milk or water and top it with a handful of nuts, seeds, and dried fruits for a fiber-rich and energy-boosting breakfast.

Lunch Options:

  1. Salmon Salad with Mixed Greens: Combine grilled or baked salmon with mixed greens, cherry tomatoes, cucumbers, and a light dressing for a protein-packed and refreshing lunch.

  2. Lentil Soup with Whole-Grain Bread: Prepare a hearty lentil soup using lentils, vegetables, and broth, and pair it with whole-grain bread for a satisfying and fibre-rich meal.

  3. Quinoa Salad with Chickpeas and Vegetables: Toss together cooked quinoa, chickpeas, a variety of chopped vegetables, and a light vinaigrette for a plant-based and protein-rich lunch.

  4. Turkey and Avocado Sandwich on Whole-Grain Bread: Layer sliced turkey, mashed avocado, lettuce, and tomato on whole-grain bread for a lean protein and fibre-packed sandwich.

Dinner Options:

  1. Baked Chicken with Roasted Vegetables: Bake chicken breasts alongside a medley of roasted vegetables, such as broccoli, carrots, and zucchini, for a balanced and delicious meal.

  2. Shrimp Scampi with Whole-Wheat Pasta: Sauté shrimp in a light garlic and white wine sauce and toss it with whole-wheat pasta for a protein-rich and satisfying dinner.

  3. Grilled Salmon with Quinoa and Asparagus: Grill salmon fillets and serve them alongside quinoa and steamed asparagus for a nutrient-dense and tasty meal.

  4. Lentil Shepherd's Pie with Mashed Cauliflower: Prepare a lentil-based shepherd's pie topped with a creamy mashed cauliflower topping for a hearty and vegetarian-friendly dinner.

Remember to prioritise nutrient-dense foods such as fruits, vegetables, whole grains, and lean proteins during your eating periods to support your weight loss goals and overall well-being. Stay hydrated throughout the day, even during fasting periods, by consuming plenty of water. Consult your doctor or a registered dietitian for individual dietary advice and support.

What is a fasting period? In the context of intermittent fasting (IF), a fasting period refers to a designated time when you abstain from consuming any calories. During fasting periods, your body undergoes a metabolic shift, transitioning from utilizing glucose, its primary energy source derived from food, to breaking down stored energy reserves, primarily fat. This process, known as ketosis, occurs when glycogen stores deplete, prompting the liver to produce ketones, alternative energy molecules that fuel the body during fasting intervals.

The length of fasting periods can vary depending on the specific IF method you choose. Some popular IF methods include:

  1. 16/8 Method: This weight-loss method requires abstaining from food for 16 hours daily and confining meals to an 8-hour period, commonly between noon and 8 pm

  2. 5:2 Diet: This dietary approach involves consuming normal meals for five days of the week while limiting calorie intake to 500-600 calories on two separate days.

  3. Eat-Stop-Eat: This is when you are fasting for an entire 24 hours which happens once or twice a week. The amount of time you stop eating here is crucial.

During fasting periods, it is essential to stay hydrated by consuming plenty of water and unsweetened beverages, such as tea and black coffee. Is there a risk of cancer or liver disease from intermittent fasting? Intermittent fasting (IF) has gained widespread popularity as a dietary strategy associated with weight loss and various health benefits. However, concerns have arisen regarding its potential impact on cancer and liver health. While research is still ongoing, emerging evidence suggests a nuanced interplay between IF and these health risks.

Cancer and Intermittent Fasting

Several studies have explored the potential link between IF and cancer. Some findings suggest protective effects, such as a 2016 study published in Cell Reports that demonstrated IF's ability to slow tumor cell growth in mice. Similarly, a 2018 study in Cancer Research indicated that IF reduced the risk of breast cancer development in mice.

However, other studies have raised concerns about potential cancer risks associated with IF. A 2022 meta-analysis published in Nature Reviews Cancer concluded that IF's impact on cancer risk remains inconclusive, with some studies showing no significant effect and others suggesting increased risk for certain cancer types.

Liver Health and Intermittent Fasting

The relationship between IF and liver health has also garnered attention. While some studies hint at protective effects, such as a 2022 review in Nutrients suggesting IF's potential to improve liver function in non-alcoholic fatty liver disease (NAFLD) patients, other studies raise concerns.

A 2021 study published in Liver International indicated that IF could exacerbate liver steatosis, a fatty liver condition, in mice with NAFLD. Similarly, a 2022 study in Digestive Diseases and Sciences found that IF worsened liver inflammation in mice with NAFLD.

How much weight can you expect to use with intermittent fasting? The amount of weight you can expect to lose with intermittent fasting (IF) depends on several factors, including your starting weight, activity level, and overall diet. However, studies have shown that people who follow IF can lose an average of 7-11 pounds (3-5 kg) in 10 weeks.

Here is a breakdown of how much weight you can expect to lose with different types of IF:

  • 16/8 method: People who follow this method can expect to lose an average of 7 pounds (3.2 kg) in 10 weeks.

  • 5:2 diet: People who follow this diet can expect to lose an average of 9 pounds (4.1 kg) in 10 weeks.

  • Eat-Stop-Eat: People who follow this method can expect to lose an average of 11 pounds (5 kg) in 10 weeks.

It is important to note that these are just averages, and the amount of weight you lose may vary. Some people may lose more, while others may lose less. The best way to determine how much weight you can expect to lose with IF is to talk to your doctor or a registered dietitian.

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