Intermittent fasting: What is it, and how does it work?

Intermittent fasting has become one of the world’s most popular approaches to improving health and managing weight. Unlike traditional diets that focus on what you eat, intermittent fasting focuses on when you eat. Many people find it easier to follow because it doesn’t require counting every calorie or eliminating entire food groups.

Research suggests that intermittent fasting may help with weight management, improve insulin sensitivity, support heart health, and even promote better metabolic function. However, it isn’t a magic solution, and understanding how it works is essential before getting started.

Whether you’re considering a simple 12-hour overnight fast or the widely followed 16:8 method, this comprehensive guide covers everything you need to know, including the benefits, potential risks, best fasting schedules, common mistakes, and answers to the most frequently asked questions.

What Is Intermittent Fasting?

Intermittent fasting (IF) is an eating pattern that alternates between periods of eating and fasting. During the fasting window, you avoid consuming calories, allowing your body to use stored energy.

Unlike many diets, intermittent fasting doesn’t tell you which foods to eat. Instead, it focuses on creating structured eating and fasting windows.

Popular fasting schedules include:

• 12:12 – Fast for 12 hours and eat during the next 12 hours.
• 14:10 – Fast for 14 hours with a 10-hour eating window.
• 16:8 – Fast for 16 hours and eat within 8 hours.
• 18:6 – Fast for 18 hours and eat within 6 hours.
• 20:4 – Also known as the Warrior Diet.
• 5:2 Method – Eat normally for five days and significantly reduce calories on two non-consecutive days.

Among these, the 16:8 method is the most popular because it is practical, sustainable, and supported by a growing body of research.

Health Benefits of Intermittent Fasting

When combined with a healthy diet and active lifestyle, intermittent fasting may offer several benefits.

Supports Weight Loss

Intermittent fasting naturally reduces the amount of time available for eating, helping many people consume fewer calories without consciously restricting food.

Improves Insulin Sensitivity

Lower insulin levels during fasting may help improve blood sugar regulation, particularly in people with insulin resistance.

Encourages Fat Burning

As glycogen stores become depleted, the body increasingly relies on stored fat for energy.

Supports Heart Health

Some studies suggest intermittent fasting may improve:

• Blood pressure
• Cholesterol levels
• Triglycerides
• Inflammation

May Improve Brain Health

Research indicates fasting may stimulate brain-derived neurotrophic factor (BDNF), a protein involved in learning and memory.

Simplifies Eating

Many people appreciate the simplicity of having fewer meals to plan and prepare.

Popular Intermittent Fasting Methods

12:12 Method

Ideal for beginners.

Example:

• Dinner: 7 PM
• Breakfast: 7 AM

This schedule aligns well with natural overnight fasting.

14:10 Method

A gentle progression for those comfortable with 12-hour fasting.

16:8 Method

The most widely practiced schedule.

Example:

• Fast: 8 PM–12 PM
• Eat: 12 PM–8 PM

18:6 Method

Suitable for experienced fasters seeking additional structure.

5:2 Diet

Normal eating on five days, with calorie restriction (typically 500–600 calories) on two non-consecutive days.

How Do You Perform Intermittent Fasting?

Starting intermittent fasting doesn’t have to be difficult.

Follow these steps:

1. Choose a fasting schedule that fits your lifestyle.
2. Stay well hydrated throughout the day.
3. During fasting, drink water, black coffee, or unsweetened tea.
4. Break your fast with a balanced meal containing protein, fibre, healthy fats, and whole grains.
5. Avoid binge eating during your eating window.
6. Exercise regularly, adjusting workout intensity based on your energy levels.
7. Prioritise good sleep, as poor sleep can increase hunger.

Consistency is more important than fasting for extremely long periods.

Foods to Eat During Your Eating Window

Focus on nutrient-dense foods such as:

Protein

• Eggs
• Fish
• Chicken
• Paneer
• Tofu
• Greek yogurt
• Lentils

Healthy Fats

• Nuts
• Seeds
• Avocados
• Olive oil

Complex Carbohydrates

• Brown rice
• Oats
• Sweet potatoes
• Whole wheat
• Millets

Fruits

• Apples
• Berries
• Oranges
• Guava
• Papaya

Vegetables

Fill half your plate with colourful vegetables for fibre and nutrients.

Drinks Allowed During Fasting

Generally acceptable options include:

• Water
• Sparkling water
• Black coffee (without sugar or milk)
• Plain green tea
• Black tea
• Herbal tea without sweeteners

Adding sugar, milk, cream, fruit juice, or flavoured syrups typically breaks a fast because they contain calories.

What Is Not Allowed During Intermittent Fasting?

During the fasting period, avoid foods and drinks that contain calories, including:

• Sugary beverages
• Fruit juices
• Soft drinks
• Milk
• Cream
• Sweetened coffee or tea
• Alcohol
• Snacks
• Candy
• Biscuits
• Protein shakes
• Smoothies

Even small amounts of calories may interrupt the fasting state, depending on your goals.

Common Mistakes When Intermittent Fasting

Many beginners struggle because of avoidable errors.

Eating Too Much

Some people overeat during the eating window, cancelling the calorie deficit.

Poor Food Choices

Intermittent fasting doesn’t compensate for a diet high in processed foods.

Not Drinking Enough Water

Hydration is essential for reducing headaches and fatigue.

Starting Too Aggressively

Jumping directly into 20-hour fasts often leads to poor adherence.

Ignoring Sleep

Sleep deprivation increases hunger hormones and cravings.

Expecting Immediate Results

Healthy weight loss takes time.

Who Should Avoid Intermittent Fasting?

Intermittent fasting may not be appropriate for everyone.

Consult your healthcare provider if you:

• Are pregnant or breastfeeding
• Have diabetes requiring medication
• Have a history of eating disorders
• Are significantly underweight
• Have certain chronic medical conditions
• Take medications that require food

Children and adolescents should only fast under medical supervision.

Exercise While Intermittent Fasting

Exercise is generally safe during intermittent fasting.

Many people prefer:

• Walking
• Strength training
• Yoga
• Cycling
• Light cardio

Some individuals enjoy fasted morning workouts, while others perform better after eating. The best approach depends on your energy levels and fitness goals.

How Long Does It Take to See Results?

Results vary depending on:

• Starting weight
• Calorie intake
• Physical activity
• Sleep
• Metabolism

Many people notice:

• Reduced bloating within 1–2 weeks
• Weight loss within 2–4 weeks if maintaining a calorie deficit
• Improved energy and appetite control after several weeks

Sustainable weight loss is generally around 0.5–1 kg per week, although individual results vary.

Tips for Success

• Start with a 12-hour fast.
• Increase fasting gradually.
• Eat balanced meals.
• Include enough protein.
• Stay hydrated.
• Avoid processed foods.
• Exercise regularly.
• Get adequate sleep.
• Be consistent rather than perfect.

Frequently Asked Questions (FAQs)

1. Is it better to fast 12 or 16 hours?

It depends on your goals and experience. A 12-hour fast is an excellent starting point and fits naturally into an overnight schedule. A 16-hour fast may offer greater metabolic benefits for some people and is commonly used for weight management, but it is not necessarily better for everyone. The best fasting duration is one you can maintain consistently.

2. What are the rules for intermittent fasting?

The basic rules include:

• Follow a consistent fasting schedule.
• Consume no calorie-containing foods or drinks during the fasting window.
• Stay hydrated.
• Eat nutritious meals during your eating window.
• Avoid overeating.
• Get enough sleep and exercise regularly.

3. Can I lose 10 kg in 2 months with intermittent fasting?

Losing 10 kg in two months is possible for some people, particularly those with a higher starting weight, but it is not realistic or healthy for everyone. A safer and more sustainable target is 0.5–1 kg per week through intermittent fasting, a balanced diet, and regular physical activity.

4. How do you perform intermittent fasting?

Choose a fasting schedule, such as 12:12 or 16:8, avoid calorie-containing foods during the fasting period, stay hydrated, and eat balanced meals within your eating window.

5. Is fasting from 7 PM to 7 AM good?

Yes. Fasting from 7 PM to 7 AM provides a 12-hour overnight fast, making it an excellent and sustainable option for beginners while supporting healthy eating habits.

6. What is not allowed during intermittent fasting?

Avoid anything containing calories during the fasting window, including sugary drinks, milk, cream, juices, snacks, sweets, alcohol, and protein shakes.

7. What is the golden rule of intermittent fasting?

The golden rule is don’t overeat during your eating window. Intermittent fasting works best when combined with healthy food choices, portion control, and consistency.

8. What happens after 7 days of intermittent fasting?

After one week, many people notice reduced bloating, improved appetite control, and better meal timing. Some may also experience modest weight loss, though results vary depending on diet and activity levels.

9. Can I eat fruits during intermittent fasting?

Yes, but only during your eating window. Fruits provide vitamins, minerals, fibre, and natural sugars, making them a healthy part of a balanced diet.

10. Why is 16 hours the magic number for fasting?

Sixteen hours isn’t truly “magic,” but it provides enough fasting time for many people to shift toward greater fat use while remaining practical and sustainable. It’s one of the most researched and commonly followed fasting schedules.

11. Can I eat a banana while intermittent fasting?

Not during the fasting window. A banana contains calories and natural sugars, so it should be eaten during your designated eating period.

12. What’s the best time to start intermittent fasting?

Most beginners do well by starting with a 12-hour overnight fast, such as 7 PM to 7 AM, and gradually extending the fasting period if desired.

13. What are common mistakes when intermittent fasting?

Common mistakes include:

• Overeating after fasting
• Eating unhealthy processed foods
• Drinking too little water
• Skipping sleep
• Starting with excessively long fasts
• Expecting rapid weight loss

14. How long does it take to see results from 16/8 fasting?

Some people notice reduced bloating and improved appetite within the first week. Weight loss often becomes noticeable after 2–4 weeks, provided there is an overall calorie deficit.

15. Is it better to do intermittent fasting in the morning or at night?

There isn’t a single best schedule. The ideal timing is the one that matches your daily routine and can be maintained consistently. Many people find overnight fasting easier because much of the fasting period occurs during sleep.

16. Can we skip dinner instead of breakfast in intermittent fasting?

Yes. Some people skip dinner instead of breakfast, while others do the opposite. The best approach is whichever schedule helps you maintain healthy eating habits and fits your lifestyle.

17. At what hour does fat burning start when intermittent fasting?

Fat burning gradually increases as glycogen stores decline, often becoming more significant around 12–16 hours into a fast. The exact timing varies depending on factors such as recent meals, physical activity, and individual metabolism.

18. Which meal is best to skip?

There is no universally “best” meal to skip. Choose the meal that is easiest for you to miss while still allowing you to meet your nutritional needs and maintain your routine.

Final Thoughts

Intermittent fasting is a flexible eating pattern that can support weight loss and improve metabolic health when paired with nutritious food choices, regular exercise, and adequate sleep. Whether you begin with a simple 12-hour overnight fast or progress to the popular 16:8 schedule, the key is consistency rather than perfection.

Remember that intermittent fasting is not a one-size-fits-all approach. Listen to your body, choose a schedule that fits your lifestyle, and consult a healthcare professional if you have any underlying medical conditions or concerns before making significant dietary changes.