Intermittent Fasting 16/8: The Complete Guide

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Intermittent fasting has become an increasingly common approach to “dieting.”

Unlike nearly all other popular diets, such as vegan or plant-based eating, the Whole30 diet, the Atkins diet, or the paleo diet, intermittent fasting is confined and defined by when you can or can’t eat rather than by what you can and can’t eat.

There are countless ways to practice intermittent fasting, but one of the most common iterations of the time-restricting eating patterns of this dietary approach is 16 8 intermittent fasting, also referred to as intermittent fasting 16/8.

In this article, we will discuss the benefits of 16 8 intermittent fasting and tips for following the intermittent fasting 16/8 diet.

We will discuss: 

  • What Is Intermittent Fasting 16/8?
  • Benefits of Intermittent Fasting 16/8
  • Does Intermittent Fasting Promote Weight Loss?
  • Potential Drawbacks of Intermittent Fasting 16/8
  • Tips for 16:8 Intermittent Fasting

Let’s get started!

An alarm clock with a set of utensils.

What Is Intermittent Fasting 16/8?

Intermittent fasting is an umbrella term that can refer to any eating pattern marked by frequent or occasional periods of extended fasting or restricted windows of time when eating can occur.

Some people practice intermittent fasting by fasting a full day one or multiple times per week and then eating normally on other days, whereas a more common intermittent fasting style is to restrict your daily feeding time window each day, which is termed time-restricted eating (TRE) or time-restricted feeding (TRF).

Intermittent fasting 16/8 involves restricting the time period in which you eat during the day to only an 8-hour window and deliberately extending the period of fasting to 16 hours.

Most people who practice intermittent fasting 16/8 achieve their 16 hour fast by skipping breakfast and waiting until it is at least midday before they have anything to eat. 

Then, they may have nothing after dinner until a light midday meal again the next day. This means they skip breakfast entirely and may not have anything at all to drink besides water, black coffee, or plain herbal tea.

Two cups of herbal tea.

What Can You Eat While Intermittent Fasting 16/8?

There aren’t any rules regarding specifically when you can and can’t eat while intermittent fasting as long as you are only eating during your designated window of time.

During your 16 hour fast, you can only have non-caloric fluids such as water, herbal tea, or black coffee without sweeteners, milk, or cream.

The reason you can drink black coffee is that one cup (240 ml) of black coffee only contains approximately 3 calories, with just trace amounts of protein, fat, and minerals, so even a cup or two of coffee won’t really induce any metabolic changes or take you out of a fasted state.

Benefits of Intermittent Fasting 16/8

Evidence suggests that intermittent fasting may promote weight loss and reduce the risk of certain chronic diseases, such as heart disease, type 2 diabetes, and Alzheimer’s disease.

But how? 

A plate with wooden utensils.

Studies show that intermittent fasting with time-restricted eating regimens, such as 16:8 intermittent fasting, appears to influence metabolic regulation through three primary means: altering circadian biology, modifying the gut microbiome, and shifting modifiable lifestyle behaviors, such as sleep and energy intake.

Our bodies have an internal circadian clock that governs things like the sleep-wake cycle, metabolism and energetics, and hormonal secretion patterns.

The hormonal, metabolic, and energetic responses to eating seem to be somewhat dependent on our circadian rhythm such that the body secretes more insulin in response to glucose when you eat outside of the typical or expected daylight hours (such as with late-night eating), which can contribute to weight gain and insulin resistance over time.

Interestingly, the gut microbiome also has an internal circadian rhythm. Animal studies have found that intermittent fasting with time-restricted eating increases the biodiversity of the gut microbiome and shifts the composition to support weight loss rather than obesity.

Lastly, intermittent fasting can change your sleep and energy intake, both of which can have a significant effect on your metabolic hormones and weight.

Due to the hormonal and metabolic effects of time-restricted eating, 16:8 intermittent fasting can confer the following health benefits:

  • Reducing visceral or abdominal fat
  • Improving cellular health
  • Providing more freedom with food choices over other popular diets
A person eating from a plate of healthy food, a smoothie.

Does Intermittent Fasting Promote Weight Loss?

Studies show that intermittent fasting can be an effective way to lose weight.

For most people, the primary way in which intermittent fasting is a successful weight loss diet or approach to weight management is that it restricts the amount of time you can eat, so you naturally eat less food.

In other words, by confining your permissible eating time to a restricted window, you physically don’t have as much time to eat food, so your daily caloric intake will be less.

For example, many people are prone to late-night eating or taking a sort of grazing, buffet approach to mindless eating all day.

While this might not involve gorging on a huge meal all in one sitting, the total number of calories can still really add up.

With 16:8 intermittent fasting, your eating window is confined to just eight hours, which literally puts a hard stop to your daily munching.

A plate of breakfast and lunch, with dinner covered by the word fasting, an example of intermittent fasting.

Moreover, because the eating window is fairly short and the 16-hour fast is long and can be uncomfortable if you don’t prepare, many people find that 16:8 intermittent fasting makes them more mindful of their food choices during the eating window.

This, in turn, can also promote weight loss because you are choosing more satiating, nutrient-dense foods that will keep you full over the fast.

Instead of eating a greasy pizza or a big bowl of white pasta, which can leave you feeling ravenous the next morning, you might be motivated to choose more nutritious foods that provide sustained energy and fullness, such as salmon and quinoa with broccoli.

Finally, adding to the behavioral changes with intermittent fasting that support weight loss, there can be positive shifts in your mindset towards eating and food as well.

As touched upon, restricting the eating window to eight hours by following intermittent fasting 16/8 can make you more mindful about your food choices and portions because you want to be sure you’re maximizing your nutrition and satisfaction with food when you can actually eat.

This is sort of akin to the economics principle of scarcity.

A plate, clock, tape measure and fork.

If you think of your restricted feeding window as a limited resource, the value of its stock goes up.

In other words, if, before intermittent fasting, you used to be able to physically eat XYZ amount of food in a day, your choices didn’t really matter because you had time and space to eat whatever you wanted.

However, if you only have a limited amount of time to eat because of 16:8 intermittent fasting, you might only have time to eat X amount of food now.

Therefore, your choices become more valuable. You won’t want to “waste” your food choices on things you don’t really want or need.

Again, this can make you be more deliberate and mindful about everything you’re putting in your mouth, cutting down on mindless munching and poor food choices.

Finally, some people find themselves thinking about food most of the day. They wake up thinking about breakfast. They are already mentally planning a mid-morning snack as they finish their first meal. 

They dream about dinner before lunch is even over, and so on.

This mild obsessiveness can lead to binging, food addiction, emotional eating (and thus weight gain), or just to placing undue importance on food that the person would rather not harbor.

Time-restricted eating, with intermittent fasting, can, in some cases, cut back on the mental space that food is occupying in your head.

Some people find they think about food less during the day because it’s a smaller portion of their day.

It’s important to note that the opposite can also be true. Some people find that restricting their eating window makes them obsess about it all day and binge once it’s time to break the fast.

A plate of healthy food, a smoothie and a clock.

Potential Drawbacks of Intermittent Fasting 16/8

Intermittent fasting doesn’t work well for everyone. If you have diabetes or issues regulating your blood sugar, a history of an eating disorder, are pregnant or breastfeeding, or have certain other medical conditions, you should speak to your healthcare provider before starting intermittent fasting.

Additionally, if you are an endurance athlete or training heavily for a sport, 16:8 intermittent fasting might be a challenging eating pattern to maintain while properly fueling your workouts.

Although not impossible, runners and endurance athletes are encouraged to work with a sports nutritionist or registered dietitian if they’re interested in following intermittent fasting with long fasts, like intermittent fasting 16/8.

There are potential drawbacks to 16:8 intermittent fasting, including the following:

  • Headaches
  • Lightheadedness
  • Low blood sugar 
  • Difficulty fueling and recovering from workouts
  • Moodiness and irritability 
  • A tendency to binge when the eating window opens 

Note that you may or may not experience these drawbacks depending on what you eat during your eating window, your activity level, and your overall health status.

A glass of water being poured.

Tips for 16:8 Intermittent Fasting

It’s important to remember that intermittent fasting is really just a tool, and its success as a weight loss diet is contingent upon how you use the strategy and your food and lifestyle choices

Here are some tips for intermittent fasting 16/8:

  • Try to avoid gorging or overeating when your eating window begins by planning your meals ahead of time.
  • Keep a food diary to track how you feel and what meals satiate you the most.
  • Be mindful of your diet quality. Focus on minimally-processed whole foods such as high-quality lean proteins, vegetables, eggs, fruit, seeds, legumes, and healthy fats like avocados and nuts.
  • Be deliberate in the timing of your workouts relative to your eating and fasting windows so that you are well-fueled and able to refuel afterward.
  • Listen to your body to determine if you’re feeling better or worse after starting intermittent fasting.
  • Feel free to play around with your eating and fasting windows, and adjust accordingly. You don’t have to keep the same schedule every day.

Intermittent fasting can be a successful and sustainable dietary regimen for some people, but it’s important to remember that your metabolism, physiology, lifestyle, and preferences are unique. 

The diet that works best for you may be different than what works best for someone else.

If you are interested in doing a 24-hour or 36-hour fast, check out our guides!

A white plate and utensils and a gold alarm clock.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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