Fasting has become an increasingly popular way to lose weight quickly. Many diets like intermittent fasting and alternate day fasting use fasting as a core component. Fasting is the practice of abstaining from food and caloric beverages for a set period of time. It allows the body to enter a metabolic state called ketosis, which promotes fat burning. The duration of the fasting window plays a key role in determining weight loss results. This article provides a comprehensive overview of how many hours of fasting are required to lose weight effectively.
How Fasting Promotes Weight Loss
Fasting promotes weight loss in several ways:
Induces Ketosis
Ketosis is a metabolic state where the body starts burning fat for fuel instead of carbs. It is triggered when carb intake is very low, as is the case during fasting. Fasting for 16-48 hours can drastically increase ketone levels, which suppresses appetite and accelerates fat burning. This metabolic switch is extremely beneficial for weight loss.
Lowers Insulin Levels
Fasting causes a drastic reduction in insulin levels. This increases lipolysis, allowing your body to access and burn its fat stores for energy. Lower insulin also reduces insulin resistance which makes weight loss easier.
Increases Adrenaline
Fasting increases adrenaline and noradrenaline levels in the blood. These hormones help break down body fat and free fatty acids for fuel. Higher adrenaline also maintains metabolic rate despite calorie restriction.
Reduces Calories
Fasting directly results in an overall reduction in calories consumed. Lower calorie intake puts your body in a calorie deficit which forces it to burn fat stores. The longer the fasting duration, the lower the calories.
How Many Hours of Fasting Are Needed Per Day to Lose Weight?
The number of fasting hours needed per day depends on the specific protocol being followed. Here is an overview of common intermittent fasting protocols and the minimum fasting hours per day required to lose weight:
16/8 Intermittent Fasting
This involves fasting for 16 hours a day and restricting feedings to an 8 hour window. You would fast for 16 hours every day and eat regular meals within the 8 hour window.
16 hours of fasting can trigger ketosis and effectively aid weight loss for most people. It is the most popular and sustainable intermittent fasting protocol.
Alternate Day Fasting
This fasting protocol entails alternating between fasting days where you eat 500-600 calories and feed days where you eat regular meals without restrictions.
On fasting days, you would fast for 24 hours to lose weight with alternate day fasting. This equals 2-3 full non-consecutive fasting days per week.
5:2 Diet
This intermittent fasting approach involves eating regular meals 5 days a week while severely restricting calories to 500-600 for 2 days.
On the 2 fasting days, you would fast for 24 hours. This equals 48 hours of fasting per week spread over 2 days.
Eat Stop Eat
Eat stop eat fasting involves fasting completely 1-2 times per week and eating normally on other days.
Each fasting day would require fasting for 24 hours straight. If done twice a week, this equals 48 hours of fasting.
How Many Hours of Fasting Per Week to Lose Weight?
Most research indicates that fasting for over 48 hours per week can boost weight loss:
- Fasting for 72 hours per week may result in 7-11 lbs of weight loss over 4 weeks.
- Fasting for around 60 hours weekly can lead to 3% body fat loss in 6 weeks.
- Completing a 24 hour fast once or twice weekly equals 48-72 hours fasting weekly for weight loss.
The more hours spent fasting, the greater the potential weight loss. However, fasting for longer than 48 hours per week is challenging to maintain. It is not recommended for beginners either.
Experts suggest starting with 16/8 or 24 hours 1-2 times per week. You can gradually build up to 60-72 hour fasting weeks for accelerated fat burning.
Optimal Hours of Fasting Per Day
The best fasting window per day depends on your lifestyle, schedule and preferences. Here are the top options:
16-Hour Fast
A 16 hour daily fast is the most convenient and sustainable approach for beginners. It simply requires skipping breakfast and restricting feedings to 8 hours like 12pm to 8pm. 16 hours includes your sleeping period.
18-20 Hour Fast
Fasting for 18-20 hours daily can maximize fat burning while still being manageable. You would eat within a 4-6 hour window each day – like from 1pm to 5pm or 12pm to 6pm. It may require skipping breakfast and dinner.
24 Hour Fast 1-2 Times Per Week
Doing one or two complete 24 hour fasts per week is also very effective. It provides metabolic benefits without daily restriction. However, 24 hour fasting periods can be challenging.
36 Hour Fast 1-2 Times Per Month
Occasional 36 hour fasting periods 1-2 times per month provide excellent fat burning effects. However, this type of extended fasting should only be done occasionally – not daily.
What are the Best Fasting Hours for Weight Loss?
Research indicates that the following fasting windows and durations provide the best results for weight loss:
- 16-20 hours daily – the most sustainable and effective daily fasting period for steady weight loss over weeks/months.
- 24-36 hours 1-2 times per week – optimal for intermittent fasting 1-2 days weekly with strong weight loss benefits.
- 60-72 hours per week – accelerates weight loss but requires building up to. Best for short term fat loss spells of several weeks.
- Overnight fasts of 10-12 hours – very manageable and allows body to enter fat burning mode while sleeping.
Aim for the 16-20 hour fasting window as a beginner until your body adapts. Then you can increase fasting duration and frequency to boost results.
Conclusion
In summary, research shows that fasting for 16-48 hours per week can effectively aid fat loss. Beginners can start with 16 hour daily fasts or 24 hour fasts 1-2 times weekly. You can gradually progress to 60-72 hour fasting weeks for more aggressive weight loss. Overnight fasting for 10-12 hours is also beneficial. The key is to experiment and find a sustainable fasting routine that suits your lifestyle. Any fasting duration over 16 hours per day will help you lose weight by kickstarting ketosis.