How many hours should you fast? That depends a lot on the length of your fast. Your fasting time is not determined by the number of hours you choose to eat within that time frame. You’ll be eating for 12 hours, and fasting for 12 (8pm until noon or so) if you’re following this intermittent fasting protocol. This post will go over everything you need to know about how many hours you should be fasting for weight loss and health purposes.
What is intermittent fasting?
This is a popular type of fast that requires less commitment than prolonged fasting. It involves alternating between periods of eating and fasting either within one day or over several days and therefore can be practised potentially indefinitely. Crucially, it is not a conventional diet as it does not restrict what you eat during feasting periods. There are many types of intermittent fast, including alternate day fasting, the 5:2 and the one meal a day fast (OMAD).
Additionally, time restricted eating (TRE) alternates between periods of fasting and eating within one day, for example the 12:12, the 16:8 and the more intensive 20:4 [8]. Everyone practises TRE to some extent during sleep, therefore extending this natural fast is an easy way to incorporate TRE into any lifestyle.
Fasting, the intentional restriction of calorie intake over a period of time, has numerous health benefits including weight loss, protection against disease and improved longevity [1]. It comes in many forms, the most popular for weight loss being prolonged (lasting longer than two days) and intermittent (alternating between cycles of fasting and feasting). Both methods have different advantages and disadvantages depending on your lifestyle –but which is better for weight loss?
How does fasting work?
Caloric restriction promotes weight loss through the process of ketosis, during which the body metabolises fat for energy. Around 12-16 hours into a fast, blood glucose and insulin levels drop and the nutrient signalling pathways that are regulated by the mTOR kinase protein are deactivated
This forces the body into the fasting state and it starts to switch from using glucose from food for energy to metabolising fat stores, producing ketones that are oxidised by the brain. As food is reintroduced, nutrient signalling pathways are reactivated and ketosis plateaus. This process can promote weight loss as well as improve metabolic function, reduce inflammation and enhance immune functioning. Weight loss has numerous benefits to health and longevity, reducing the risk of morbidity from heart disease, stroke, type 2 diabetes and some cancers
Ketosis has the additional advantage of burning fat supplies without using protein, making it possible to continue weight training for maintaining and growing muscle during caloric restriction
What is prolonged fasting?
The human body has adapted to withstand long periods of food deprivation, with the longest fast ever recorded lasting 382 days
Prolonged fasting is an extreme form of caloric restriction that lasts for two days or more. Usually, they last anywhere between 2-5 days to a maximum of two weeks and are only broken by the consumption of water and plain tea or coffee. For those new to fasting, it is recommended that you practise intermittent fasts of increasing lengths before trying prolonged, as your body becomes adjusted to ketosis
For example, start out with the 12:12 intermittent fast before moving on to a 24-hour fast and finally a two-day prolonged fast.
How does fasting work?
Caloric restriction promotes weight loss through the process of ketosis, during which the body metabolises fat for energy. Around 12-16 hours into a fast, blood glucose and insulin levels drop and the nutrient signalling pathways that are regulated by the mTOR kinase protein are deactivated
This forces the body into the fasting state and it starts to switch from using glucose from food for energy to metabolising fat stores, producing ketones that are oxidised by the brain. As food is reintroduced, nutrient signalling pathways are reactivated and ketosis plateaus. This process can promote weight loss as well as improve metabolic function, reduce inflammation and enhance immune functioning. Weight loss has numerous benefits to health and longevity, reducing the risk of morbidity from heart disease, stroke, type 2 diabetes and some cancers
How Many Hours You Need to Fast to Lose Weight
It’s no question that fasting is an effective way to lose weight. In fact, Patricia Bannan, MS, RDN, and LA-based nutritionist and healthy cooking expert has explained before that intermittent fasting, which is an eating pattern that cycles between bouts of eating and calorie restriction, is an especially powerful way to blast fat.
“Intermittent fasting causes glucose (sugar) concentrations to decrease and lipolysis (fatty acid oxidation) to increase significantly during the first 24 hours, which helps the body break down stored fat,” she said.
However, there are many different methods of intermittent fasting, the most popular of which is likely the 16/8 method, which entails skipping breakfast and eating between an 8-hour time frame, followed by a 16-hour fast. A new study conducted by researchers from the University of Illinois at Chicago found that fasting just a few hours of the day was enough to help people lose about 3% of their body weight in roughly two months.
The study, which was published in the journal Cell Metabolism, compared the results of two different time-restricted feeding diets, where participants were asked to fast for 20 and 18 hours, respectively.
“This is the first human clinical trial to compare the effects of two popular forms of time-restricted feeding on body weight and cardiometabolic risk factors,” said Krista Varady professor of nutrition at the UIC College of Applied Health Sciences.
Here’s how it worked. Those who participated in the 20-hour fast ate whatever they wanted between 1:00 p.m. and 5:00 p.m. and for those who were assigned the 18-hour fast were allowed to eat until 7:00 p.m. During the fasting periods, participants were allowed to drink water as well as other calorie-free beverages. The control group was asked to maintain weight and not make any changes to their diet or physical activity levels.
The result? After 10 weeks, participants in both fasting groups reduced their caloric intake by about 550 calories a day, enabling them to drop (on average) 3% of their body weight. In addition, researchers also discovered that both insulin resistance, which can lead to type 2 diabetes, and oxidative stress levels were reduced in those who fasted in comparison with those who didn’t in the control group.
In short, both fasting periods were effective and lead to nearly identical weight loss results.
“The findings of this study are promising and reinforce what we’ve seen in other studies—fasting diets are a viable option for people who want to lose weight, especially for people who do not want to count calories or find other diets to be fatiguing,” Varady said. “It’s also telling that there was no added weight loss benefit for people who sustained a longer fast—until we have further studies that directly compare the two diets or seek to study the optimal time for fasting, these results suggest that the 6-hour fast might make sense for most people who want to pursue a daily fasting diet.”
How Long Does Intermittent Fasting Take To Show Results?
You might begin to first notice a difference in your body about 10 days after you begin intermittent fasting. It could take between 2-10 weeks for you to lose significant weight. You might lose up to a pound each week.
Usually, the first signs you will notice that scream that your intermittent fasting is working is less bloating. Your midsection might look trimmer just over your first week of intermittent fasting.
Observing weight loss will take a little longer as your body needs some time to adjust to this new diet.
At about the second week is when most people first notice that they have dropped their first few pounds. If you have still not lost any weight by week two, stay consistent for about four or five more weeks and your results should come in soon enough.
How Much Weight Can You Lose From Intermittent Fasting
Intermittent fasting is not a quick weight loss fix. It might take your body a few weeks to start shedding the extra pounds.
Do not expect to drop up to 20 pounds within your first week of intermittent fasting.
Like many diets, you need to remain consistent and make lifestyle changes to get results.
It might take a few weeks for you to drop your first pound from intermittent fasting. However, once you start, you can expect to lose about a pound each week. Some people can lose up to 10 pounds each month.
Therefore, your body type will determine your results.
Why You Are Not Shedding Weight With Intermittent Fasting
So, you have been fasting intermittently for up to eight weeks without losing weight or you have gained more pounds.
Let us take a look at a few reasons delaying your intermittent fasting results.
You Are Eating The Wrong Type Of Food
Many other diets come with a list of foods that you can and cannot eat. However, that is not how intermittent fasting works.
Intermittent fasting lets you eat anything you would like within a specific eating window.
Because intermittent fasting does not restrict your diet, it is easy to slip right into unhealthy feeding habits. Binging on unhealthy processed foods even if it is only in your eating window could be responsible for your slow results.
Stuffing too many calories during your eating periods is also counterproductive.
During your intermittent fast, consider changing your meal plan. Toss out the unhealthy processed food and switch to healthier options. Think of foods like whole grains that are rich in dietary fiber.
Furthermore, sugary foods could send your blood sugar levels through the roof and contribute to reduced insulin sensitivity[3].
Staying away from sugary foods protects you from sugar highs and the sugar crash that results after. It also helps keep your blood sugar within the normal range.
You Are Not Drinking Enough Water
If you are reading, drink some water right now. Intermittent fasting restricts your meal times but places no restrictions on water drinking throughout the day.
Drink enough water to stay hydrated during your fast. You can also take tea or black coffee to replenish your lost fluids without breaking your fast.
Drinking water can keep you full till your next eating period. Therefore it keeps you from snacking and packing on extra calories.
Staying hydrated is important for your overall health. If you are exercising, you ought to drink even more water to replace what you lost through sweat.
You might also need to change your lifestyle to include better sleep if you are thinking of starting intermittent fasting.
You Are Not Eating Enough Food
Though it might sound counterproductive, you need to eat well during your eating window.
Intermittent fasting does not mean starvation and you can continue with your normal diet.
When you are not getting enough calories during your eating window, chances are that you will eat a whole lot more during your next window. That is because of the uncontrollable hunger that you will feel.
Also, starving yourself might cause your body to store more fat long-term[4]. Your body notices that you are going for extended periods with little or no food and to ensure that you have a reliable energy source during such periods, your body stores the extra food you eat as fat.
So, instead of burning energy from your meals, your body begins to conserve energy.
Calorie counting could help you ensure you are getting sufficient fuel for your day’s activities.
Your Fasting Window Is Too Short
If you want to notice a difference in your body weight, your eating window during your intermittent fasting diet should be significantly less than normal.
If the difference between your eating window before and during intermittent fasting is only an hour or two, you might barely notice significant weight loss.
A 14-hour fasting window with a 10-hour eating window seems like a great place to start. However, if you find the 14 hours to be too long, you could start with a shorter fasting duration and work your way up.
You Keep Breaking Your Fast
If you are used to snacking in between meals, staying without food for an extended fasting period could be difficult and affect your intermittent fasting results.
Consistently breaking your fast before your fasting window is up could be responsible for your lack of progress with intermittent fasting.
Your fasting period might be too long and switching your eating schedule a bit might be helpful. Consider reducing your fasting period to about 10-12 hours and begin to increase it as time goes on.
Moving up slowly allows your body to get used to going extended periods without food, therefore, you are less likely to break your fast prematurely.
When you can tolerate going longer without food, you could move up to the 16:8 intermittent fast. Here, you will have eight hours for feeding.
You Are Not Eating Enough Protein
If you find that your meals cannot carry you across your fasting period to your next eating window, then you might need to adjust your diet.
Consider including more lean protein in your diet. It does not matter the type of protein, vegan or animal protein, all are fine.
Proteins can help keep you full[5] till your next meal. Furthermore, if you are exercising during this period, proteins are important for building your muscles and protecting your bone health.
Your meals should have healthy fats, carbs, leafy greens, and proteins.