The 16/8 intermittent fasting method is a daily time-restricted eating schedule where you fast for 16 consecutive hours and eat only during the remaining 8 hours of the day. In practice, this often means skipping either breakfast or dinner.
For example, you might eat all your meals between 12:00 pm and 8:00 pm, then fast overnight until noon the next day. Outside of the 8-hour window, no calorie-containing foods or drinks are consumed. Water, black coffee, and herbal tea are generally allowed.
This pattern became popular through fitness communities, notably Martin Berkhan’s “Leangains” protocol, and has since been adopted broadly for health and weight loss. The origin of the 16/8 intermittent fasting method lies in its simplicity and compatibility with daily life. By only narrowing the eating window, it doesn’t dictate what foods to eat, only when to eat them.
Many beginners find it an accessible introduction to intermittent fasting because the 16-hour fast includes your normal overnight sleep.
A typical daily schedule on the 16/8 intermittent fasting method might look like:
- 8:00 PM: Finish your last meal of the day (window closes).
- 8:00 PM – 12:00 PM next day: Fasting period (16 hours overnight and morning). Drink water, black coffee, or tea as needed.
- 12:00 PM: Break your fast with lunch (window opens).
- 12:00 – 8:00 PM: Eating window of 8 hours. Consume lunch, an optional snack, and dinner within this period.
This structure can be adjusted earlier or later to fit your routine. Some prefer 10 am-6 pm, others 1 pm-9 pm. The key is consistency: aim for roughly the same eating hours each day so your body’s clock adapts.
Sixteen hours of fasting gives your body an extended break from digestion, which proponents believe triggers various healthful processes.
This is just one of several intermittent fasting approaches. For a full breakdown of popular methods, visit our Intermittent Fasting Methods page.
How Does the 16/8 Intermittent Fasting Method Work?
During a 16-hour fast, your body undergoes a series of metabolic shifts that make intermittent fasting unique. After you finish your last meal, blood sugar and insulin levels begin to fall as you enter the fasted state.
By around 12 hours into fasting, the body has used up much of its readily available glucose and starts burning stored fat for energy, producing ketones as fuel. This metabolic switch can aid weight loss by tapping into fat reserves. Additionally, fasting gives your digestion a rest and may spur cellular maintenance processes.
Research suggests that time-restricted eating “pushes” cells to focus on repair and triggers autophagy, a cleanup process where cells remove and recycle damaged components. In essence, the 16/8 method works not by magic but by creating a daily calorie deficit and optimizing hormonal balance.
Biologically, the 16:8 intermittent fasting method can also align with circadian rhythm fasting principles when you choose the right hours. Our bodies are more insulin-sensitive and metabolically active earlier in the day, so setting your 8-hour window between 9 a.m. and 5 p.m. may help you leverage your natural body clock for better glucose control and energy balance.
However, even if your window is later (e.g., skipping breakfast and eating until evening), you are still extending the nightly fast well beyond the standard overnight period. During fasting hours, insulin stays low, which can facilitate fat burning and possibly improve insulin sensitivity over time.
Benefits of 16/8 Fasting
The 16/8 intermittent fasting method has been studied in both clinical trials and real-world settings, and it shows a range of potential benefits, especially for weight management and metabolic health.
Below are some evidence-based benefits of the 16/8 intermittent fasting method:
Weight Loss and Fat Reduction
One of the primary reasons people adopt 16/8 is to lose weight. Research supports that it can be effective.
In a 12-week pilot study on obese adults, those following a 16/8 time-restricted eating schedule ate about 350 fewer calories per day and lost roughly 3% of their body weight. They also saw a 7 mmHg drop in systolic blood pressure on average. Notably, participants were not required to count calories as the weight loss came naturally from the restricted time window.
Heart Health Markers
Short-term 16/8 fasting has been linked to improvements in certain cardiovascular risk factors. For example, the same 12-week study noted above found lower blood pressure in the 16/8 group.
Other research and reviews have noted reductions in LDL (“bad”) cholesterol and triglycerides with intermittent fasting, though results can be mixed. Overall, research reviews indicate IF can reduce blood pressure, improve cholesterol profiles, and decrease markers of inflammation in the short term.
Metabolic Flexibility and Autophagy
By routinely extending the fasting period, the 16/8 intermittent fasting method may train the body to better switch between burning carbs and burning fat for fuel. After ~12-16 hours of fasting, you deplete stored glycogen and begin to mobilize fat, potentially entering mild ketosis. This can improve metabolic flexibility, the body’s ability to efficiently use different fuel sources.
Simplicity and Lifestyle Fit
Beyond clinical measures, an important benefit of 16/8 is its relative ease and flexibility. There are no complicated rules besides timing, and no special foods or purchases required. This makes it sustainable as a long-term habit for many.
As researcher Krista Varady notes, “there are options for weight loss that do not include calorie counting… the 16:8 diet is another tool… one of the benefits may be that it is easier for people to maintain.”
Drawbacks and Challenges of 16/8
While 16/8 fasting is considered one of the more sustainable IF methods, it’s not without its challenges and potential downsides. It’s important to approach this eating pattern with realistic expectations and awareness of what could go wrong.
Here are common drawbacks and challenges associated with the 16/8 method:
Hunger and Adjustment Period
Especially in the first week or two, you will likely experience hunger pangs during the fasting hours. If you’re used to eating breakfast early, for instance, pushing your first meal to noon can cause morning hunger, irritability (“hanger”), and difficulty concentrating initially.
The good news is that many people adapt after 1-2 weeks as the body’s ghrelin (hunger hormone) rhythm adjusts. Side effects like headaches, dizziness, and constipation tend to subside after the early adjustment period.
Social and Lifestyle Constraints
Only eating within an 8-hour window can conflict with social norms, depending on how you schedule it. For example, if your family or friends typically enjoy big breakfasts, skipping that meal can isolate you from those social eating experiences.
Alternatively, if you stop eating by 7 pm, you might have to decline late-night dinners or snacks at social gatherings. Skipping either breakfast or dinner can impact social life – breakfast meetings or evening outings that involve food become tricky.
Potential Overeating or Nutrient Gaps
Some individuals may respond to the 8-hour window by overeating or choosing poor foods because they feel extra hungry or “entitled” to indulge after fasting. If one breaks the fast with very large, high-calorie meals or eats continuously throughout the 8-hour window, it can erase the calorie deficit and even lead to weight gain.
Additionally, fitting all your nutrition into two meals a day means you have to plan carefully to meet your needs for protein, fiber, vitamins, and minerals. Skipping an entire meal can create nutrient gaps if you don’t compensate.
Unclear Long-Term Risks (and One Notable Study)
The long-term effects of the 16/8 intermittent fasting method are still uncertain. While short-term research shows benefits, extended use hasn’t been fully studied.
A 2024 observational study of 20,000 U.S. adults found that those eating within an 8-hour window had a 91% higher risk of cardiovascular death over 15 years compared to those with >12-hour eating spans.
Experts stress caution: the study was associational, based on self-reported timing, and may reflect preexisting health issues. For now, mainstream experts recommend monitoring health markers like blood pressure and labs if practicing 16/8 long term, since risks may vary by individual.
Not Suitable for Everyone
Certain individuals should not attempt the 16/8 intermittent fasting method (or any fasting) without medical guidance. For example, pregnant or breastfeeding women, people with a history of eating disorders, and individuals with certain medical conditions should avoid strict fasting routines.
Additionally, if you are very active in the mornings or have a physically demanding job, skipping breakfast might initially impair your performance or safety. Low blood sugar during heavy labor or intense workouts can be an issue. These challenges don’t mean 16/8 is “bad,” but they underscore the need to personalize the approach.
Who Should Try the 16/8 Method?
Let’s break down who might benefit most from the 16/8 intermittent fasting method, and who should avoid it or seek medical advice before trying it:
Ideal Candidates for 16/8
- Adults Looking for Weight Loss or Weight Maintenance: If you have excess weight and struggle with traditional calorie-counting diets, 16/8 can be a great alternative. It naturally limits calorie intake and has research-backed weight loss results.
- Individuals with Busy or Structured Schedules: If you’re someone who “forgets to eat” breakfast or doesn’t mind delaying meals, 16/8 fits well. Many working professionals enjoy not worrying about breakfast on rushed mornings. They can have coffee/tea and focus on work, then have a hearty lunch.
- People Interested in Health Span and Metabolic Health: Even if weight loss isn’t the primary goal, folks interested in potential metabolic or longevity benefits might try 16/8. There is intrigue around intermittent fasting for improving insulin sensitivity, possibly reducing the risk of type 2 diabetes, and inducing cellular repair mechanisms.
- Those Who Prefer Larger Meals and Fewer Eating Occasions: If you dislike “grazing” or small, frequent meals and instead enjoy eating a couple of bigger meals, 16/8 can be psychologically satisfying. Within your 8-hour window, you might have just lunch and dinner (and perhaps a small snack), but those meals can be reasonably substantial.
- People with some experience in fasting or skipping meals: If you’ve successfully done shorter fasts (like the occasional 24-hour fast or a 14/10 pattern) and felt okay, moving to a 16/8 routine is a logical next step. Your body is likely already somewhat accustomed to extending the time between meals.
Who Should Avoid or Be Cautious
- People with a History of Eating Disorders: Leading clinics warn that IF patterns like 16/8 are not healthy for those with eating disorders. In these cases, a regular, balanced meal schedule is usually safer for recovery and mental health.
- Pregnant or Breastfeeding Women: During pregnancy and lactation, the body has increased energy and nutrient needs to support the baby. Fasting for long stretches could deprive the mother and baby of steady nutrition.
- Individuals with Diabetes or Serious Medical Conditions (unless under medical supervision): While some people with type 2 diabetes have used intermittent fasting to improve their condition, this must be done under close medical guidance. Similarly, those with conditions like advanced liver or kidney disease, or who are on medications that must be taken with food at certain times, should be very cautious.
- Underweight or History of Nutritional Deficiencies: If someone’s BMI is below the healthy range or they’ve struggled with malnutrition, fasting is not appropriate. The focus should be on nutrient-dense caloric intake, not restriction.
- Those who find skipping meals extremely difficult or stressful: This might sound obvious, but if you know that going without food triggers migraines, extreme weakness, or profound unhappiness for you, 16/8 may not be the right choice. Some people simply feel better eating a healthy breakfast to start their day and might get anxious or depressed if they don’t.
How to Start the 16/8 Intermittent Fasting Method
Here are practical steps and tips on how to begin the 16/8 intermittent fasting method:
1. Pick Your Window
Decide which 8 hours of the day will work best for your eating. Popular choices are 12-8 pm, 10-6 pm, or 8-4 pm. Many people find skipping breakfast easiest, while others prefer skipping dinner for better alignment with natural rhythms. The best window is the one you can stick to consistently.
2. Ease Into It
Jumping straight into 16 hours of fasting can be tough. Try starting with 14/10 (14 hours fasting, 10 eating) for a week, then move to 15/9, and finally 16/8. Gradually pushing your first meal later each day makes the transition smoother.
3. Hydrate Generously
Water is your best ally during fasting hours. Begin your morning with a couple of glasses and keep sipping throughout the day. Black coffee, unsweetened tea, or sparkling water are also fine. If you feel lightheaded, a pinch of salt or a squeeze of lemon in your water can help balance electrolytes.
4. Plan Your Meals
When your eating window opens, it’s easy to overdo it if you don’t plan. Aim for meals built around protein, vegetables, fiber, and healthy fats. For example, a hearty chicken and quinoa salad or eggs with whole-grain toast and veggies. Balanced meals help stabilize blood sugar and keep you satisfied.
5. Manage Hunger Cues
Hunger pangs are common in the first week, often at times your body is used to eating. Keep water or tea handy, chew sugar-free gum, or distract yourself with work or a walk. Hunger usually fades within 20 minutes. Staying busy during fasting hours makes the time pass more easily.
6. Listen and Adjust
Mild hunger and fatigue are normal at first, but if you feel dizzy, irritable, or unable to function, shorten your fast temporarily. Some people thrive with a 14-hour fast, while others do better shifting their eating window earlier or later.
7. Work Out Smart
Light activity, like walking, fits well in a fasted state. If you enjoy weight training or high-intensity exercise, experiment with timing. Some do fine training fasted, others prefer exercising within their eating window. Either way, refuel with protein once your window opens.
8. Stay Consistent, Not Perfect
Aim to follow your schedule most days, but adjust when social events or family meals come up. You might shift your window later for a dinner out or earlier for a brunch. If you go off plan for a day, simply return to 16/8 the next.
Wrapping It Up: Is 16/8 Your Fit?
The 16/8 intermittent fasting method has earned its reputation as one of the most approachable styles of fasting. By sticking to an 8-hour eating window, many people see meaningful weight loss, steadier blood sugar, and improvements in heart health markers without obsessing over every calorie.
Still, it isn’t a magic fix. It comes with an adjustment period, and like any lifestyle change, it works best when paired with mindful eating and a willingness to listen to your body.
As always, check in with a healthcare professional if you have underlying health conditions or unique dietary needs. Fasting works best when we share and support each other. What’s your biggest curiosity or challenge with the 16/8 intermittent fasting method?
