Intermittent Fasting: Methods, 16:8 Plan, and Benefits

By the nucoach editorial team · Updated September 18, 2026 · approx. 12 min read

What is intermittent fasting?

Intermittent fasting is not a diet in the classic sense but an eating pattern: it determines when you eat, not what you eat. The day or the week is divided into phases with and without food intake, and during the fasting phases you only have calorie-free drinks.

The idea behind it is old: over millennia, the human body has coped with periods without food and developed mechanisms for it. In the first hours after a meal, it uses the energy it has just taken in; then it draws on the carbohydrate stores in the liver and muscles, and only when these run low does fat metabolism take a bigger share of energy production. This is exactly the switch that intermittent fasting aims to bring about regularly.

In practice, though, another point matters more than the biochemistry: an eating window of 8 hours automatically limits the opportunities to eat. The late dinner in front of the TV, the 11 p.m. snack, the breakfast eaten out of habit without being hungry all drop out. For many people, that is the easiest way to eat less without counting calories, and it is the real reason the method works. The connections behind this are explained in the weight loss guide.

Which intermittent fasting methods are there?

The methods differ in the length of the fasting phase and in whether you fast daily or only on certain days. For beginners, the daily time-window methods are the most accessible.

The recommendation for getting started is clear: begin with 12:12, work up through 14:10 to 16:8, and stay there. The longer fasting windows and the one-meal variant bring no added benefit for most goals, but they significantly raise the risk of cravings, muscle loss, and a drop in performance during training. 5:2 is an alternative for people who prefer to eat completely normally on 5 days and concentrate the restraint into 2 days, but it requires more discipline on the fasting days.

More on 5:2: on the 2 fasting days, which shouldn’t fall directly one after the other, you eat only 500 to 600 kcal, usually as one or two protein-rich, vegetable-heavy meals. On the 5 normal days, you eat as needed but without compensating. The math behind it: 2 days with a deficit of around 1,500 kcal each add up to 3,000 kcal per week, which equals a daily deficit of about 430 kcal. If you keep the normal days disciplined, you get the same effect as with 16:8, just distributed differently. If you make up for it on the normal days, the effect fizzles out.

How does 16:8 work in everyday life?

With 16:8 you set an eating window of 8 hours and eat nothing with calories outside of it. Which window is right is decided by your daily routine, not by the clock.

Most people choose noon to 8 p.m.: breakfast drops out, lunch and dinner stay, and most of the fasting happens while you sleep. If you’re hungry in the morning and can easily skip the evening, go for 9 a.m. to 5 p.m. If you eat late because family or work require it, go for 1 to 9 p.m. What matters is that the window fits your fixed commitments, because a window that clashes with the family dinner every day won’t last 2 weeks.

Allowed during the fasting phase are water, unsweetened tea, and black coffee. Anything with calories ends the fast, including a splash of milk in your coffee, juice, or beer. Diet drinks are calorie-free and technically allowed, but many people deliberately fast without sweeteners because in some people they stimulate appetite. A typical 16:8 day with a window from noon to 8 p.m. looks like this: water and coffee in the morning, the first meal at noon with a clear protein source, a snack around 4 p.m., dinner at 7 p.m., and after that only water or tea. The 16 hours of fasting run from 8 p.m. in the evening until noon the next day, and you sleep through half of that.

Here is what 3 typical 16:8 days can look like, depending on your daily routine:

All 3 variations involve fasting for 16 hours, but they differ in when daily life calls for food. With the standard window, the night owl would sit at the family table every evening without eating along, and it’s exactly such conflicts that end most attempts at fasting. So: look at your daily routine first, then set the window.

What does the transition feel like?

The first 1 to 2 weeks are the hardest, after which most people report that the morning hunger goes away and the window becomes a habit. If you know what’s coming in week 1, it’s easier to get through.

Hunger comes in waves, not as a constant state. The feeling of hunger is tied to your usual mealtimes and initially shows up exactly when breakfast used to be. The wave usually lasts 15 to 20 minutes and then subsides, even without food. A large glass of water, a coffee, or a short walk gets you through it. After about 10 days, the release of the hunger hormone adapts to the new window, and the morning hunger stops.

Headaches and fatigue in the first week often have 2 causes that have nothing to do with the fasting itself: too little fluid, because breakfast also included drinks, and caffeine withdrawal if you cut out coffee. Both are easy to fix: 2 to 3 liters over the course of the day, and black coffee stays allowed. If you sweat a lot or train a lot, you can add a pinch of salt to your water during the fasting phase to support your electrolyte balance.

After 2 to 3 weeks, many people report 3 effects: clearer satiety, because real hunger returns between meals; fewer thoughts about food, because the clock takes over the decision; and a more stable energy level in the morning. If you don’t notice these effects after 4 weeks and instead think about food constantly, you should lengthen the window or switch methods. Both are legitimate.

Does intermittent fasting help you lose weight?

Yes, but for a different reason than many people think: it helps because it makes the calorie deficit easier, not because the fasting itself burns fat. Studies that compare intermittent fasting with conventional calorie restriction at the same calorie intake find similar results for both approaches.

That’s not bad news but an honest assessment: intermittent fasting is a tool for eating less, and for many people a very good one. If you’ve failed so far because of snacking, evening nibbling, and eating without being hungry, the fixed window gives you a clear rule that doesn’t use up willpower on every single decision. The clock answers the question “can I eat this now?” That is exactly what makes the method easier for many people to stick with than counting calories.

The flip side: if you eat more in your eating window than before, because the fasting built up hunger or because “I fasted, after all” counts as a free pass, you won’t lose weight. The 8-hour window is no protection against a surplus; it’s just a structure. That’s why it’s worth looking at the overall balance even with intermittent fasting: how much energy you burn and where your deficit should be is shown in the guide How to Calculate a Calorie Deficit. Once you know your number, you quickly see whether the window works for you.

Intermittent fasting or counting calories: Which is right for whom?

Both paths lead to the same goal, the deficit. The difference lies in which kind of rule is easier for you in everyday life: a time rule or a quantity rule.

Combining both is the best path for most people: the time window provides the structure and cuts out the snacks, and 2 to 3 weeks of tracking show how much actually adds up within the window. After that, you know your standard meals and need neither app nor scale. If you constantly struggle with the window but like to plan, you’re better off with 3 to 4 fixed meals and a rough calorie orientation. There is no prize for the harder method.

What else does intermittent fasting do, and what’s a myth?

Besides weight loss, many effects are attributed to intermittent fasting. Some are plausible and have been observed in studies; others are marketing. The honest breakdown:

The practical conclusion: decide for or against intermittent fasting based on whether it makes eating easier for you, not because of promised miracle effects. If you do well with the window, snack less, and feel energized, you’ve found a good tool. If you’re constantly hungry, crash in the afternoon, and overeat in the evening, a classic split into 3 to 4 meals is the better choice. Both get you to the goal if the balance is right. What really influences energy expenditure is explained in the guide Boost Your Metabolism.

The 4-week starter plan

The most common mistake is jumping from 3 meals plus snacks straight to 16:8. If you shorten the window in 3 steps, you get your body and mind used to it without cravings derailing the changeover.

Two rules for all 4 weeks: the eating window stays the same on 6 out of 7 days so the rhythm settles in, and on one day a week it may be shifted or skipped if family, a celebration, or work demand it. A fasting plan that allows no exceptions won’t survive the first birthday party. And after week 4, you decide honestly. If the window stresses your daily life, that’s not a failure but information that a different structure suits you better.

What do you eat in your eating window?

The shorter window makes the quality of your meals more important, not less. In 8 hours, you have to fit in protein, vegetables, fiber, and energy, otherwise something is missing at the end of the day.

Protein first: 1.6 to 2.2 g per kilogram of body weight per day, spread across the 2 to 3 meals in the window. At 70 kg, that is 110 to 150 g of protein, so a good 50 g per meal, which corresponds to roughly 200 g of low-fat quark or 180 g of chicken breast or 250 g of skyr. Protein keeps you full the longest, protects muscle in a deficit, and is the first thing to fall short when fasting, because many people fill the first meal with carbohydrates. Which foods deliver the most protein per serving is listed in the guide High-Protein Foods.

Then volume: vegetables, salad, legumes, fruit. They fill you up for few calories and provide the fiber that tends to be missing when you fast. The plate method is the simplest rule: half vegetables, a quarter protein source, a quarter side such as potatoes, rice, or whole grains.

And the most important rule: no compensation. Fasting is not permission to make up for everything within the window. If you start with a pizza plus dessert after 16 hours of fasting, you’ve blown the day’s balance within 30 minutes. That’s why the first meal should be planned, with protein and volume, so that hunger doesn’t make the choice. If you also want to safeguard your deficit within the window with simple strategies, you’ll find them in the guide Weight Loss Tips.

An example eating window from noon to 8 p.m. with around 1,600 kcal: at noon, a large bowl with 150 g of chicken or tofu, plenty of vegetables, a portion of rice, and olive oil, about 600 kcal. At 4 p.m., 250 g of skyr with berries and a handful of nuts, about 350 kcal. At 7 p.m., salmon or lentils with roasted vegetables and potatoes, about 650 kcal. That makes 3 meals, around 130 g of protein, plenty of volume, and no hunger crash before the next lunch.

How do intermittent fasting and training fit together?

They go together well if you keep 2 things in mind: intense training belongs in the eating window or right before it, and the meal after training must not be skipped.

Easy endurance training, walks, mobility work, and yoga work fine on an empty stomach in the morning for most people, and some even feel more alert doing it. Strength training and intense intervals are a different matter: without energy in your stores, performance drops, and without protein after the session, the material for recovery is missing. If you train hard at 7 a.m. and don’t eat until noon, you give away part of the training effect and risk muscle loss in a deficit.

The practical solution: coordinate your training times and your eating window. If you train in the evening, set the window to noon to 8 p.m. and eat after the workout. If you can only train in the morning, shift the window to 9 a.m. to 5 p.m. and train right before the first meal, or accept that the window starts 30 minutes earlier on training days. The rule of “16 hours to the minute” is less important than the meal after training. What a strength training plan for beginners looks like and why it’s indispensable in a deficit is covered in the guide Strength Training for Beginners, and nutrition around your workouts in the guide Muscle Building Nutrition.

Which mistakes are typical?

Most people who give up on intermittent fasting do so for the same 5 reasons, and all of them can be avoided.

A sixth point that is often overlooked: sleep. If you stretch your window to 10 p.m. and go to bed at 11 p.m., you often sleep worse because digestion is still working. A gap of 2 to 3 hours between the last meal and sleep improves sleep quality for many people, and good sleep stabilizes the hunger hormones, which are challenged during fasting anyway.

Who is intermittent fasting not suitable for?

For healthy adults, intermittent fasting is a safe eating structure. In some situations, however, the decision belongs in a doctor’s hands, and in others the method is unsuitable.

Intermittent fasting is not suitable during pregnancy and breastfeeding, for children and teenagers, if you are underweight, and with a history of eating disorders, because fixed fasting rules can reactivate old patterns there. You should have it checked by a doctor if you have diabetes, especially with medication tied to meals, with heart, kidney, or liver conditions, with low blood pressure, with thyroid conditions, and with any medication that has to be taken with food. If you exercise a lot or do hard physical work, you should choose a more generous window so that enough energy fits in.

One honest note to finish: if fasting leads to brooding over food, a compulsion to control, or fear of the window after 4 weeks, that is a sign to stop, regardless of weight. An eating structure should free your mind, not occupy it. In that case, a conversation with a doctor or a qualified nutrition professional is the right step.

Frequently asked questions about intermittent fasting

This guide is for general information and does not replace medical or nutrition therapy advice. If you have pre-existing conditions, take medication, are pregnant or breastfeeding, or if the topic of food weighs heavily on you, talk to your doctor before you start. You can find, compare, and book verified coaches in the nucoach app, for Berlin and Hamburg.