What is 16/8 and 12/12 Intermittent Fasting?


Fasting diets have become increasingly popular in recent years due in large part to the fact that they do provide noticeable results. But with so many different types of fasting diets, it can be difficult to choose the one that best works for you. Extensive research is required to learn all there is to know about these diets. You probably don’t have time to conduct that research, so here’s a breakdown of two of the most popular fasting diets, the 16/8 and the 12/12 intermittent fasting diets. 

What are Fasting Diets?

Fasting is the dietary practice of cycling between periods of fasting and eating. It should be noted that the vast majority of fasting diets do not say anything about which foods to eat or not eat, but rather when you should eat them. We already ‘fast’ every day while we’re sleeping, taking a 6-10 hour break from eating. Sometimes, fasting can be as simple as extending that period a little longer. 

Fasting has become a popular diet trend in recent years, but it has been commonplace in certain cultures for centuries. For example, religions and philosophies that practice fasting include Buddhism, Christianity, Islam, Judaism, Taoism, Jainism, and Hinduism. These fasts can last for a few hours or even a few weeks. During these religious fasts, most practitioners will eat at night and fast during the day. 

Is Fasting Healthy?

If you are relatively healthy and stay hydrated during a fast, fasting for a few days shouldn’t cause any issues. Most fasting diets, such as the 16/8 and 12/12 intermittent fasting diets, are safe for healthy individuals. However, most doctors recommend fasting for a long period of time. 

This is because your body needs vitamins, minerals, and other nutrients from food in order to function properly. If you don't get enough, you can have symptoms such as fatigue, dizziness, constipation, dehydration, and not being able to tolerate cold temperatures. Fasting too long can be life-threatening. If you have diabetes, you should avoid even short fasts as it can lead to dangerous dips and spikes in blood sugar. Women who are pregnant or breastfeeding should also avoid fasting. 

12/12 vs 16/8 Intermittent Fasting

Intermittent fasting has become one of the most popular dietary trends in recent years with the two most common forms being the 12/12 and 16/8 diets. The main difference, and really the only difference, between the two diets, is how long the fasting period lasts. As you can probably tell by the names, the 12/12 diet has a 12-hour eating window and a 12-hour fasting window. The 16/8 diet has an 8-hour eating window and a 16-hour fasting window. 

Later in this article, we will discuss what the research says regarding which one works more than the other. Keep in mind, however, that the diet that best works for you will largely depend on personal preference. Many people do not wish to go 16-hours without eating in which case, the 12/12 diet makes more sense. 

Can You Fast While on the Keto Diet?

Those who keep up with health trends will already know how big of a boom both intermittent fasting and keto diets have made in recent years. Now, many people are wondering if you should combine the two to get optimized results. The main idea behind the keto diet is to help your body reach ketosis, the process in which your body breaks down fats to form substances called ketones that serve as an alternate fuel source. This diet can be an incredibly effective way to lose weight. 

Believe it or not, researchers believe that intermittent fasting may help your body reach ketosis quicker than the keto diet alone. This is because your body, when fasting, maintains its energy balance by shifting its fuel source from carbs to fats which is the exact premise of the keto diet. While it’s safe to combine the two if you’re healthy, it’s unnecessary to combine both. 

Does the 16/8 Diet Really Work? 

There is research that points to the idea that there’s virtually no difference between those who partake in intermittent fasting versus those who simply cut back their calorie intake. Some believe the better strategy is optimizing the nutritional quality of what you already eat. Also, science suggests any potential benefit from fasting is quickly undone during the eating part of the cycle, in which appetite-suppressing hormones switch gears to make you feel even hungrier than you felt at baseline.

However, an intermittent fasting diet plan 16/8 can be very beneficial for those who have trouble sticking to prescribed meal plans or restrictive diets. It should be noted that fasting provides benefits that extend beyond losing weight. Fasting can give your vital organs, digestive and absorptive hormones, and metabolic functions a break. It can also induce autophagy, which is the body’s way of replacing old, dying cells with newer, healthier cells. This can help improve your longevity, leading to a longer, healthier life. 

What are the Benefits of Intermittent Fasting?

As we mentioned previously, the benefits of intermittent fasting extend beyond weight loss. There is a mound of evidence that points to intermittent fasting providing full-body benefits as well as brain benefits. Here are some of the benefits of intermittent fasting, whether it be 16/8 or 12/12:

  • Lowered risk of type 2 diabetes - Fasting can reduce your insulin resistance, which can help lower blood sugar levels, protecting against type 2 diabetes
  • Reduce oxidative stress and inflammation - Oxidative stress can oftentimes lead to chronic diseases. Fasting can help enhance your body’s resistance to oxidative stress, fighting off inflammation
  • Improved heart health - Intermittent fasting has been shown to improve numerous different risk factors, including blood pressure, total and LDL cholesterol, blood triglycerides, inflammatory markers, and blood sugar levels
  • Prevent cancer - While more research is needed, current research does show that fasting can help prevent cancer
  • Brain health - Fasting can induce bodily functions, such as autophagy, which help reduce oxidative stress, reduce inflammation, and reduce blood sugar levels

When considering starting a fasting diet, you should consider all of these benefits, on top of the weight loss aspect of the diet. 

Intermittent Fasting Diet Plan

So what exactly does an intermittent fasting diet plan look like? Keep in mind, these diets do not dictate what foods you should or shouldn’t eat. These diets dictate how many hours during the day you can eat. Here are some common types of intermittent fasting (1):

  • The 16/8 method - As mentioned earlier, this method involves a 16-hour fasting window. While this may sound extreme, it can be as simple as not eating anything after dinner and skipping out on breakfast
  • 12-hour intermittent fasting - This plan has a 12-hour fasting window. This can be as simple as skipping out on breakfast
  • 5:2 diet - This diet involved eating normally five days of the week and restricting your calorie intake to 500-600 for two days of the week. It is highly recommended that you space these days out
  • Eat Stop Eat - The Eat Stop Eat diet is a more extreme version of the 5:2 diet. This diet requires you to eat normally five days a week, and fast for 24-hours for two days. You can accomplish this by eating dinner one night and waiting a full 24-hours to eat dinner again. You don’t necessarily have to go the entire day without eating
  • The Warrior Diet - This diet is essentially an all-day fast with a small eating window. The idea is that you only eat small amounts of vegetables and fruits throughout the day, then a large meal at night

As you can tell, some of these diets are more extreme than others. Before starting a diet that requires 24-hour fasting windows, you should consult with your doctor to ensure it’s safe. These diets are not intended for pregnant women or those with diabetes. 

How Often Should You Do The 16 8 Intermittent Fasting? 

Since 16:8 fasting diet plans aren’t as extreme as diets that require full 24-hour fasting windows, you can repeat this cycle as much as you want. Some practice the diet once or twice a week while others practice it every day. How often you do it can be personal preference. You can also ease your way into the diet as you see fit. 

It can’t be stressed enough that you should consult with your doctor before beginning any diet, especially a diet that involves fasting. If at any point during the fast you begin to feel nauseous, light-headed, or dizzy, you should stop the fast and eat something, preferably something nutritious, as soon as possible. These are signs from your body that you are in desperate need of nutrients for energy. 

What is Allowed During Intermittent Fasting? 

As you may imagine, there is no food allowed during the fasting period. However, you can drink water, coffee, tea, and other non-caloric beverages during the fast. Depending on the diet, you may be allowed to eat low-calorie foods, but on diets such as the 16:8 and 12:12 diet, there are no snacks during the fasting period. 

You can take supplements during fasting as long as there are no calories inside of the supplements. In fact, many doctors may recommend taking supplements in order to get your body the nutrients it needs during the fasting period. Supplements allow you to get the benefits of a fast while still getting the nutrients, vitamins, and minerals you need to stay healthy. 

What Happens After Not Eating For 12 Hours?

The main benefit of fasting is that your body is forced to look inside for energy rather than using carbohydrates and other nutrients from foods for energy. During the first 12 hours of a fast, your body begins to use stored fats for energy. This is why fasting is such a popular dietary method for those who are looking to lose weight quickly. 

Another reason why fasting helps you lose weight quickly is that it reduces your calorie intake, simply because you’re not eating. By partaking in fasting you may find it easier to cut back on calories every day. The energy restriction from a 12-hour fast may also benefit your metabolism, helping in weight loss.

What Happens To Your Body When You Fast For 16 Hours?

The 16/8 intermittent diet is one of the most popular intermittent diets because it’s easy to follow, flexible, and is sustainable for the long term. The fasting window isn’t extreme and there are no strict calorie restrictions. It can also help you count down the amount of money you spend on food, so think of that as an added benefit. Here are some of the health benefits of fasting for 16-hours:

  • Weight loss - Fasting for 16-hours can boost your metabolism, quickly increasing weight loss
  • Improved blood sugar control - Fasting for 16-hours has been shown to reduce insulin levels by up to 31% and lower blood sugar by 3-6% (2)
  • Enhanced longevity - Fasting can help you live a longer, healthier life

The benefits of a 16:8 diet are essentially the same as a 12/12 diet. What diet works best for you will largely depend on what you’re hoping to get out of your diet. 

Supplements Can Help

One supplement that can help you get the most out of your fasting diet is spermidine supplements. This is because spermidine helps induce something called autophagy. This is the body’s process of replacing old and potentially damaged cell parts with healthier new ones. Autophagy literally means ‘self-eat.’

This process helps keep you feeling and looking young while also lowering your chances of developing aging diseases such as Parkinson’s and Alzheimer’s. While it is possible to get your recommended daily intake of spermidine through your diet, it’s recommended to take supplements so you ensure you get the right dose. Simply taking your supplements with your dinner is a great way to remember to take spermidine supplements every night. 




  1. 6 Popular Ways to Do Intermittent Fasting
  2. 16/8 Intermittent Fasting: A Beginner's Guide