Intermittent fasting has become an increasingly popular way to lose weight and burn fat. But how exactly does intermittent fasting help your body start burning fat?

This article will explore the science behind intermittent fasting and fat burning.

Intermittent fasting is a type of diet that involves alternating between periods of eating and fasting.

There are several different intermittent fasting schedules, such as 16:8 (fasting for 16 hours and eating within an 8 hour window) or 5:2 (eating normally 5 days a week and fasting 2 days).

The idea behind intermittent fasting is that it allows your body to enter a fasting state which triggers fat burning.

What Happens to Your Body When You Fast?

When you eat throughout the day, your body is constantly digesting and absorbing food. This means your insulin levels remain elevated, which signals your body to store excess calories as glycogen or fat.

During a fasting period, your body eventually runs out of glycogen stores. This causes insulin levels to drop and triggers your body to start burning fat for fuel instead of glucose.

Specifically, prolonged fasting causes your body to produce ketone bodies from your fat stores. Ketone bodies replace glucose as your body’s main source of energy.

This metabolic state, called ketosis, allows your body to burn fat efficiently.

How Does Intermittent Fasting Boost Fat Burning?

Practicing intermittent fasting primes your body to start burning fat for fuel. Here’s how it works:

• Lowers insulin levels – Fasting for 12-24 hours keeps insulin levels low. This allows your body to access its fat stores more easily.
• Increases fat burning hormones – Fasting increases levels of the fat burning hormone norepinephrine (noradrenaline).
• Triggers ketosis – As mentioned, fasting triggers ketone production which signals your body to start burning fat rather than carbs.
• Enhances fat breakdown – Fasting increases the activity of fat-digesting enzymes lipase and hormone-sensitive lipase.

Multiple studies demonstrate that intermittent fasting can boost fat burning and promote weight and fat loss. Participants tend to lose significant fat, especially around the belly and thighs area.

The Different Stages of Intermittent Fasting

When you first start intermittent fasting, your body goes through various stages of fat burning:

1. Glycogen depletion – For the first few hours of fasting, your body burns through your glycogen (glucose) reserves. Blood sugar and insulin levels start to drop.

2. Gluconeogenesis – As glycogen stores are used up, your body creates new glucose from amino acids. This maintains normal blood sugar levels.

3. Ketosis – After burning through glycogen, your body switches to burning fat in the form of ketone bodies. This is when significant fat-burning begins.

4. Protein conservation – After prolonged fasting, your body conserves protein by suppressing gluconeogenesis. Ketone bodies fully replace glucose as the main energy source.

5. Starvation response – If fasting is extended for multiple days, your body enters “starvation mode” and starts breaking down muscle tissue. This causes metabolic slowdown to conserve energy.

The key fat burning stage is ketosis, which starts around 12-16 hours into a fast. This demonstrates the mechanism behind intermittent fasting schedules like 16:8.

What Are The Benefits of Intermittent Fasting for Fat Loss?

Here are some of the top benefits of incorporating intermittent fasting:

• Burns fat stores for energy
• Targets stubborn belly and thigh fat
• Boosts fat burning hormones
• Triggers ketosis for fat breakdown
• Helps retain calorie-burning lean muscle
• Suppresses appetite and controls cravings
• Simplifies your diet by restricting eating window

Studies demonstrate intermittent fasting can help people lose up to 8% of their body fat. Participants also decreased their body mass index and waist circumference.

What Are The Different Types of Intermittent Fasting Schedules?

There are several evidence-based intermittent fasting plans to choose from:

• 16:8 method – Fast for 16 hours per day and restrict eating to an 8 hour window. One of the most popular plans.
• Eat-Stop-Eat – Do a 24 hour fast once or twice per week. For example, finishing dinner Monday evening and not eating again until Tuesday evening.
• 5:2 diet – Eat normally 5 days per week. On 2 non-consecutive days, restrict intake to 500-600 calories.
• Alternate day fasting – Alternate between fasting days (500 calories) and feast days where you eat normally.
• Periodic fasting – Do a full 24-36 hour fast once per week or every two weeks. Water, tea and black coffee allowed during fasts.

Experts recommend starting with more gradual fasts like 16:8 before progressing to full 24-36 hour fasts. Listen to your body and be cautious if you have any medical conditions.

A Sample Intermittent Fasting Schedule To Burn Fat

An effective intermittent fasting schedule for fat loss could look like this:

• Monday – 16 hour fast (8 hour eating window)
• Tuesday – 16 hour fast
• Wednesday – 16 hour fast
• Thursday – 24 hour fast
• Friday – 16 hour fast
• Saturday – Eat normally
• Sunday – Eat normally

This combines the popular 16:8 method with a full 24 hour fast once per week. You get the benefits of ketosis from the prolonged fasts which primes your body for burning fat.

Be sure to stay hydrated with water and unsweetened tea or coffee. Focus your diet on lean proteins, healthy fats and veggies when eating. Avoid added sugars and refined carbs.

Tips for Starting Intermittent Fasting

Here are some tips to help you succeed with intermittent fasting:

• Gradually ease into longer fasts to avoid headaches and hunger pangs
• Stay busy and active to distract yourself from food cravings
• Drink plenty of water, tea and black coffee during fasts
• Avoid caloric sweeteners that can trigger cravings (even in coffee!)
• Get enough rest, especially around longer 24+ hour fasts
• Listen to your body and break fasts if you feel unwell
• Stick to a nutrition-focused eating plan when not fasting
• Add some mild exercise like walking to burn extra fat

The key is to start slow and tune in to how your body responds as you transition to fat burning mode. Patience and consistency will pay off as you see the pounds start to melt away!

The Bottom Line

Intermittent fasting provides a simple, sustainable way to enhance fat burning and lose excess body fat.

By cycling extended fasting periods with strategic eating windows, intermittent fasting keeps insulin low while increasing fat burning hormones like norepinephrine.

This metabolic shift triggers your body to start tapping into fat stores for fuel.

Research shows intermittent fasting can specifically target stubborn belly and thigh fat while helping retain calorie-burning lean muscle. Choose an intermittent fasting protocol that fits your lifestyle and stick with it. Pair your fasting regimen with a healthy, low-sugar diet and regular exercise.

Be patient through the adaptation phase as your body learns to burn fat for fuel. Over time, the pounds will start coming off and you’ll begin to feel the benefits of intermittent fasting.

Summary of Key Points:

• Intermittent fasting involves cycling between periods of eating and fasting
• Fasting promotes fat-burning by lowering insulin and increasing fat burning hormones
• Prolonged fasting triggers ketosis which shifts your body’s main fuel source to fat
• Intermittent fasting can help reduce overall body fat and target stubborn areas like the belly
• Start with gradual fasts like 16:8 before progressing to 24+ hour fasts 1-2 days per week
• Stay hydrated, limit sugars and carb-rich foods and be patient during your transition to fat burning

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Frequently Asked Questions About Intermittent Fasting

If you’re new to intermittent fasting, you probably have a lot of questions about how it works, the different protocols, and how to get started. Here we’ll cover some of the most common questions:

What happens to my metabolism when I fast?

Some worry that fasting may slow your metabolism by putting your body into “starvation mode.” However, research shows that short-term fasts of 24-48 hours actually increase your resting metabolic rate by 3-14%. Your body burns calories more efficiently and your metabolism ramps up to conserve energy and maintain current weight.

Will I lose muscle on an intermittent fasting plan?

Studies show intermittent fasting causes less muscle loss than continuous calorie restriction. Increased human growth hormone helps preserve lean muscle mass during short fasting periods. Just be sure to eat sufficient protein on non-fasting days, stay hydrated, and keep exercising.

How much weight can I lose doing intermittent fasting?

Results vary based on the individual and protocol used. But many studies show participants lose 3-8% of their body weight over 8-12 weeks of intermittent fasting. For a 200 pound person, that equals 6 to 16 pounds of weight loss.

What should I eat on non-fasting days?

Focus your diet on lean proteins like fish, poultry, eggs and plant-based proteins. Get healthy fats from nuts, seeds, avocado, olive oil. Eat plenty of non-starchy veggies and some fruits. Limit added sugar, refined grains and processed foods.

Can I exercise while fasting?

Yes, light to moderate exercise is usually fine during shorter fasts under 24 hours. Just listen to your body and stop exercising if you feel dizzy or ill. For longer fasts, schedule exercise after you break your fast and eat something.

What supplements can I take while fasting?

Common supplements to support fasting include electrolytes, BCAAs, caffeine, green tea extract and MCT oil. Avoid sugary pre-workout supplements that can spike insulin. Stay hydrated with mineral water and electrolytes.

How long should I fast for best results?

It depends on your goals and schedule. 16-20 hour daily fasts combined with 1 or 2 24-36 hour fasts per week can produce excellent fat loss results. Alternate day fasting is also effective. Build up your fasting tolerance slowly.

Can I drink coffee, tea or bone broth while fasting?

Yes, plain black coffee, unsweetened tea and plain bone broth are fine to consume during fasts. Avoid adding cream, milk or caloric sweeteners. Herbal tea and lemon water also help curb hunger.

How long until I see results from intermittent fasting?

It varies based on factors like your starting weight and which protocol you choose. Expect to see initial results in 1-2 weeks. But allow 3-6 months for more significant fat loss and body composition changes. Be patient and stick with it!

Hopefully these tips help answer some of the key questions surrounding intermittent fasting. The most important thing is to choose a sustainable protocol that fits your lifestyle so you can stick with it long term. Listen to your body, be prepared for some hunger, stay active and intermittent fasting will help you successfully lose fat.