What Is 16/8 Intermittent Fasting? A Beginner’s Guide

Intermittent fasting involves limiting your daily food intake to a certain window of time. It’s become popular for weight loss and overall health improvements. For weight loss, knowing what to eat while intermittent fasting will make a difference.

Fasting has been practiced for thousands of years and is an important tradition in many religions and cultures worldwide.

Today new varieties of fasting put a spin on this ancient practice.

One of the most popular styles of fasting is 16/8 intermittent fasting. Proponents claim that it’s an easy, convenient, and sustainable way to lose weight and improve overall health.

This article explains how to do 16/8 intermittent fasting and whether it’s right for you.

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The practice of 16/8 intermittent fasting involves limiting your intake of foods and calorie-containing beverages to a set window of 8 hours per day. You abstain from food for the remaining 16 hours, though you’re still allowed to drink water and other no-calorie beverages, like plain coffee or tea.

You can repeat this cycle as frequently as you’d like — from just once or twice per week to every day, depending on your preference.

The popularity of this fasting method has grown widely among those looking to lose weight and burn fat. 16/8 intermittent fasting is also believed to improve blood sugar control and enhance longevity ( 1 ).

While other diets often set strict rules, 16/8 intermittent fasting is simple to follow and may provide measurable results with minimal disruption to your diet. It’s generally considered less restrictive and more flexible than many other diets and works with most lifestyles.

Summary

With 16/8 intermittent fasting, you restrict your food intake to an 8-hour window and fast for the remaining 16 hours. This practice may support weight loss, improve blood sugar, and increase longevity.

This is what you need to know to do 16/8 intermittent fasting.

Choosing a time window

To get started, begin by picking an 8-hour window and limiting your food intake to that time span.

Popular 16/8 time windows include:

• 7 a.m. to 3 p.m.
• 9 a.m. to 5 p.m.
• 12 p.m. to 8 p.m.
• 2 p.m. to 10 p.m.

Many people prefer to eat between noon and 8 p.m., since you need to fast only overnight and skip breakfast but can still eat a balanced lunch and dinner, along with a few snacks throughout the day.

Others opt to eat between 9 a.m. and 5 p.m., which allows plenty of time for a healthy breakfast around 9 a.m., a standard lunch around noon, and a light, early dinner or large snack around 4:30 p.m. before starting your fast.

However, you can experiment and pick the time frame that best fits your schedule.

It may help to set timers at both the beginning and the end of your eating window to remind you when to start and stop eating.

Foods list and meal plan

To maximize the potential health benefits of your diet, it’s important to stick to nutritious whole foods and beverages during your eating periods.

Filling up on nutrient-rich foods helps round out your diet and supports a healthy weight. Try balancing each meal with a wide variety of whole foods, such as:

• Fruits: apples, bananas, berries, oranges, peaches, pears, tomatoes, etc.
• Veggies: broccoli, Brussels sprouts, cauliflower, cucumbers, leafy greens, etc.
• Whole grains: barley, buckwheat, quinoa, rice, oats, etc.
• Healthy fats: olive oil and avocados
• Protein sources: eggs, fish, legumes, meat, poultry, nuts, seeds, etc.

Drinking calorie-free beverages like water and unsweetened tea and coffee, even while fasting, also helps control your appetite while keeping you hydrated.

It’s best to limit ultra-processed foods like packaged snacks, deep-fried items, sugary drinks, and most frozen meals. These negate the positive effects of 16/8 intermittent fasting.

Summary

To begin 16/8 intermittent fasting, choose an 8-hour window and limit your food intake to that time span. Be sure to follow a balanced diet based in whole foods.

One of the main advantages of 16/8 intermittent fasting is its convenience. It can cut down on the time and money you need to spend on cooking and preparing food each week.

It has been associated with a long list of health benefits.

Increased weight loss

Restricting your eating window to a few hours per day can cut your calorie intake over the course of the day, which in turn may contribute to weight loss.

In fact, research reveals that fasting may boost weight loss.

For example, one review found that 11 of 13 studies on intermittent fasting reported statistically significant weight loss in participants ( 2 , 3 ).

Improved blood sugar control

Intermittent fasting has been shown to reduce fasting insulin and blood sugar levels, potentially decreasing your risk of diabetes ( 4 , 5 ).

Extended longevity

Evidence in humans is limited, but some animal studies note that intermittent fasting may extend longevity.

It’s thought that fasting affects metabolic pathways, improves insulin sensitivity, and leads to behavioral changes that together may lengthen your life span. However, these mechanisms aren’t fully understood ( 6 , 7 ).

Summary

Animal and human studies suggest that intermittent fasting may increase weight loss, improve blood sugar levels, and extend longevity.

Although 16/8 intermittent fasting is associated with several health benefits, it has a few side effects and may not be right for everyone.

Be sure to start your fasting regimen gradually and consider stopping or consulting your doctor if you have any concerns or experience negative symptoms.

Overeating and potential weight gain

Restricting your intake to just 8 hours per day may cause some people to eat more than usual during eating periods in an attempt to make up for hours spent fasting. This may lead to weight gain, digestive problems, and unhealthy eating habits.

Interestingly, current research doesn’t suggest that intermittent fasting leads to any more weight loss than typical diets that recommend overall calorie restriction. Both eating patterns may lead to modest weight loss ( 3 , 8 ).

If weight loss is your primary goal, you may therefore prefer to lower your calorie intake, exercise more, eat more whole foods, or sleep sufficiently instead of fasting intermittently to prevent the overeating that may occur when restricting intake to a certain time window.

In addition, weight loss may occur while fasting, but when returning to normal eating patterns, it’s common to regain the weight.

Short-term physical symptoms

The practice of 16/8 intermittent fasting may cause short-term negative side effects when you’re first getting started, such as hunger, weakness, and fatigue — though these often subside once you get into a routine.

Hormonal changes and menstrual cycles

Some animal research suggests that intermittent fasting may lead to hormonal changes and undereating. In people with ovaries, these changes may negatively affect menstrual cycles and fertility ( 9 , 10 ).

However, most studies are old and have been conducted in animals. Human studies are needed to fully understand how intermittent fasting may affect reproductive health.

Furthermore, postmenopausal individuals may experience different effects from intermittent fasting. Menopause causes changes that can decrease insulin sensitivity and lead to weight gain, and intermittent fasting may help improve these outcomes ( 11 ).

Summary

Restricting daily food intake to a particular time window may cause increased food intake and weight gain, as well as short-term hunger and weakness. Older animal studies indicate that intermittent fasting may interfere with fertility.

It’s true that 16/8 intermittent fasting can be a sustainable, safe, and easy way to improve your health when paired with a nutritious diet and healthy lifestyle.

However, it shouldn’t be viewed as a substitute for a balanced diet rich in whole foods. Plus, you can still be perfectly healthy if you don’t follow intermittent fasting.

Though 16/8 intermittent fasting is generally considered safe for healthy adults, you should talk with your doctor if you have any underlying health conditions. This is key if you’re taking any medications or have diabetes, low blood pressure, or a history of disordered eating.

Intermittent fasting is likewise discouraged if you’re trying to conceive, pregnant, or nursing.

If you have any concerns or experience any side effects while fasting, be sure to consult your doctor.

What You Should Know About the 16:8 Diet Before You Start Fasting

This popular weight-loss method can backfire if you’re not careful.

Silicon Valley moguls, celebrities, and social media influencers alike prescribe to the 16:8 diet, a form of intermittent fasting also known as the 8-hour diet. Proponents claim that restricting mealtimes — you eat during an 8-hour window each day and fast the rest of the time — helps with everything from weight loss to lowering the risk of chronic disease.

The problem with this popular method is that you’re not making decisions based on how full or hungry you feel, but rather on a restricted time window — a setup that can backfire in the long run if you’re not careful. Here’s what you need to know about 16:8 fasting before you start missing meals.

Editor’s note: Weight loss, health and body image are complex subjects — before deciding to go on this diet, we invite you gain a broader perspective by reading our exploration into the hazards of diet culture.

What is the 16:8 diet?

The 16:8 diet is a type of time-restricted fasting done to achieve better health or lose weight. (The 5:2 diet followed by Jimmy Kimmel, where you eat whatever you want five days a week and only consume 500 calories or less on the other two days, is also a modified form of fasting.)

On the 16:8 diet, you spend 16 hours of each day consuming nothing but unsweetened beverages like water, coffee, and tea. The remaining eight-hour window is when you eat all of your meals and snacks. Most people do this by starting a fast at night, skipping breakfast, and eating their first meal in the middle of the day. No foods are inherently off limits during that time, but some people will follow the keto diet at mealtimes to supercharge their weight loss.

While the term intermittent fasting (or IF) may be new to many of us, the practice isn’t all that different from the way our ancestors likely lived: Hunt, gather, and eat during daylight; sleep and fast during darkness.

Is 16:8 fasting good for weight loss?

Some studies have found that there’s virtually no difference between people who regularly practiced intermittent fasting and those who simply cut back their calorie intake overall.

A growing body of research demonstrates that a better strategy is optimizing the nutritional quality of what you already eat (veggies, fruit, lean protein, whole grains, and healthy fats) versus fasting or counting calories. 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.

But some dieters may benefit from daily fasting if they have trouble sticking to prescribed meal plans or restrictive diets; a 2018 pilot study published in the Journal of Nutrition and Healthy Eating suggests that a 16:8 fasting plan can help obese dieters lose weight without having to count every single calorie they eat. This approach to fasting could also aid those battling other weight-related issues — namely, high blood pressure. A new scholarly review published in the New England Journal of Medicine suggests that a 16:8 fasting plan may help the body naturally improve blood sugar regulation, as well as decrease blood pressure overall in the long run.

Is fasting 16 hours a day healthy?

Forms of intermittent fasting like the 16:8 diet rely on the concept that fasting reduces oxidative stress on the body, which can decrease inflammation and the risk of chronic diseases.

It’s also theorized that fasting gives your vital organs, digestive and absorptive hormones, and metabolic functions a “break,” according to a recent study published in Cell Metabolism. Since our bodies secrete insulin to help our cells absorb sugar, fasting is linked to reducing our susceptibility to insulin resistance over time. (High insulin levels ultimately put us at risk for a whole host of diseases.)

However, research has also linked fasting to increases in LDL cholesterol (the “bad” kind). Intermittent fasting can make you feel dizzy and nauseated and cause periods of low-blood sugar and dehydration. Despite the fact that most 16:8 enthusiasts drink water during fasting periods, it may not be enough (reminder: food itself provides quite a bit of water).

I also have a much deeper concern about the disordered eating behaviors that may arise from intermittent fasting. Research shows that fasting for a period of time followed by a limited window for eating primes you to overeat. It’s a cycle that can be difficult to get out of because it impairs our body’s natural hunger cues and metabolism. Restricted eating may also lead to an increased risk of depression and anxiety.

This is especially concerning for women, who have historically been more likely to develop eating disorders. The allotted periods of restriction followed by eating lends itself to binge-purge tendencies that cannot (and should not) be ignored. According to the National Eating Disorders Association, periods of fasting and binging are considered risk factors for eating disorders.

Should you try 16:8 fasting?

Ultimately, it’s a personal choice. But there are a few beneficial behaviors you can try without committing to the riskier elements of 16-hour fasts. The first is to better understand mindfulness and how it relates to your food choices. To get started, consider these questions when you’re deciding when and what to eat:

Where are you physically when you decide to eat?

Many of us eat based on scenario, not hunger levels. Case in point: Raise your hand if you’ve ever gone to the movies after dinner and suddenly wanted popcorn? Yep, me too!

By considering the moments when you eat, you may become aware of patterns you didn’t notice before. Say you’re a person who loves to graze during The Bachelor. If you’re fasting after 8 p.m., you’ve automatically cut hours — and subsequently, calories — from your post-dinner snacking.

Are you getting enough sleep?

If you’ve cut out late-night snacking, that alone could help you go to bed earlier — a very crucial component to any weight loss plan. Getting seven hours of sleep per night has been linked to better weight management, reduced risk of chronic disease, and improved metabolism.

The bottom line: It’s simply not feasible for many of us to restrict food entirely for set periods of time in order to achieve better health. In addition to being difficult socially (who wants to skip happy hour or dinners with friends?), self-imposed rules are simply not as joyful as having the right information and making choices that empower you versus hold you back. It’s best to find ways to make eating nutritious food work for you in the context of your day-to-day life. If you are considering intermittent fasting, I’d encourage you to try it by starting small and keeping it as simple as possible: Close your kitchen after dinner, aim to get more sleep, and sit down for a full breakfast at your usual time tomorrow.

A registered dietitian with a Bachelor of Arts degree from Northwestern University and a Master of Science degree in Clinical Nutrition from New York University, Jaclyn “Jackie” London handled all of Good Housekeeping’s nutrition-related content, testing, and evaluation from 2014 to 2019. Prior to joining GH, she was a clinical dietitian at Mount Sinai Hospital. Jackie has also appeared as an expert guest on The Dr. Oz Show and The Today Show. She is also author of the book Dressing on the Side (and Other Diet Myths Debunked).