Why am I not losing weight with intermittent fasting? The most common reasons

28. Juli 2026 ca. 24 Minuten

What to expect in this article

1. What intermittent fasting is and which versions there are
2. What professional associations say about the method
3. The sentence everything hinges on
4. The most common reasons the scale stops moving
5. Why the first few kilos come off quickly
6. What happens to your body as you lose weight
7. What amount is supported by evidence
8. What helps when progress stalls
9. Who the method is not intended for
10. Where a test can offer clues
11. Limitations: what a DNA test cannot do
12. What you can change starting tomorrow
Frequently asked questions
Sources

What intermittent fasting is and which versions there are

The DGE describes intermittent fasting as a form of fasting in which food is avoided for whole days or during certain hours, usually with the aim of long-term weight loss. Unlike other forms of fasting, it is intended to be followed as a long-term eating pattern (2018).

The versions differ in how long and how often food is avoided. With the 5:2 diet, you eat normally on five days and consume about a quarter of your usual energy intake on two fasting days. With alternate-day fasting, fasting days, when you also consume around 25 percent of your usual amount, alternate with unrestricted days (DGE, 2018).

The best-known version has no name in the sources

The eight-hour eating window is the most common form, and it appears in the reviewed sources without the familiar numeric label. The DGE calls it Leangains and explains that skipping breakfast results in a fasting period of about 16 hours (2018).

IQWiG describes the same thing without a name: have dinner at around 8 p.m. and then do not eat again until noon the next day. It adds a sentence that matters for this article: No diet is needed during the eight hours between lunch and dinner (as of August 24, 2022).

This very sentence is read as a free pass in many guides. It describes the method; it does not say that the amount eaten during the window does not matter.

Other variations in the sources

The DGE lists several others, too, and the list helps put what you come across online into context. With the 2-day diet, no more than 650 kilocalories are consumed on each of two consecutive days of the week, and the food choices should be low in carbohydrates and high in protein.

With dinner-cancelling, dinner is skipped two to three days a week, creating a fasting period of at least 14 hours before breakfast. With the Warrior Diet, only an evening meal is eaten each day. The DGE also counts fasting during Ramadan as a form of intermittent fasting (2018).

What this list shows is that the term covers very different approaches. So when you read that intermittent fasting works one way or another, you should always check which variation is meant.

What the professional associations say about the method

The answer to the question in the title is here, and it comes from several directions to the same conclusion.

The sentence is grammatically flawed in the original and appears that way on the page. Its meaning is clear: Weight loss comes from the amount of energy, not the timing.

What the DGE has compiled

The most comprehensive assessment comes from the German Nutrition Society and dates to 2018. Its conclusion: The available data suggested that intermittent fasting appeared to be on a par with continuous energy restriction and had no negative side effects.

More explicitly, citing a meta-analysis: Intermittent fasting is a valid alternative in terms of weight loss, fat mass and fat-free mass, but is not superior to continuous energy restriction (DGE, 2018).

The same source cites a study in which weight loss did not differ significantly between alternate-day fasting and daily energy restriction after six and twelve months. The dropout rate was 38 percent for alternate-day fasting and 29 percent for daily energy restriction (DGE, 2018).

How the IQWiG views it

The IQWiG discusses intermittent fasting under the heading of what to make of diet claims and nutrition trends. So far, there have been few studies on it, and it is especially unclear how successful the method is in the longer term and whether it works better than other weight-loss programs. In principle, however, there is nothing against trying it (as of 24.08.2022).

This is a more cautious formulation than a rejection, but it is not a promise of results either. The consumer advice center adds that so far there have been no meaningful long-term studies on the health benefits of intermittent fasting.

Where some of its good reputation comes from

Some expectations around intermittent fasting are based on studies that were not conducted on humans. The DGE notes that animal studies suggest regular food abstinence may reduce the risk of chronic diseases (2018).

Such findings are a reason for further research, not a statement about humans. The IQWiG writes elsewhere, more generally, that many studies are animal experiments, which have limited relevance to humans (2022).

For you, this means that if an article about intermittent fasting makes arguments based on cellular processes or metabolic switches, it’s worth checking who was studied.

The sentence everything hinges on

The IQWiG puts it in a nutshell: When losing weight, what matters is taking in less energy than you use. The composition of your diet is not what matters (as of 24.08.2022).

The DGE had already stated the same thing in 2012 in a specialist information sheet on meal frequency: energy balance is what determines changes in body weight. No scientifically established conclusion could be drawn about a link between meal frequency and weight regulation in healthy adults, so the DGE made no recommendation on the subject.

What this means for your eating window

If energy balance is what matters and meal frequency has no proven role, then a shorter eating window only has an indirect effect: people who have fewer opportunities to eat often eat less. The DGE describes this mechanism from the other side, noting that more eating occasions throughout the day also mean more opportunities to consume too much energy (2012).

However, this workaround only works as long as the calories aren’t made up for. Two larger meals can contain the same amount of energy as three smaller ones. This isn’t speculation, but the logical consequence of the statement above, and the reason this article had to be written at all.

Why composition matters less than expected

The IQWiG statement has a second part that is often overlooked: the composition of the diet is not decisive for weight loss (2022). The Verbraucherzentrale makes the same point when comparing the two camps, stating that for healthy people who want to lose weight, what matters is consuming fewer calories, regardless of whether it’s a low-carb or low-fat diet.

This applies to quantity, not quality. A diet can meet energy balance and still provide too few nutrients. That’s why Chapter 8 puts food choices first, even though they aren’t decisive for energy balance alone.

The most common reasons the scale isn’t moving

The following overview groups the reasons according to what the reviewed sources substantiate. It doesn’t replace looking for causes in individual cases, but it shows where there are documented explanations and where there aren’t.

What stands out in this overview is that only one of the eight reasons has to do with the method itself, and even that one concerns food choices, not the fasting schedule. Six relate to energy intake, expectations, or sticking with it, one to body composition, and one to energy expenditure.

That’s the real answer to the question in the title. If you’re not losing weight with intermittent fasting, you’re usually not doing intermittent fasting wrong.

Why the first few kilos come off quickly

Almost every change in routine shows progress in the first few days that doesn’t last. The consumer advice center describes this for the start of low-carb diets: people often lose weight quickly at first, but mostly lose 2 to 3 kilograms of water.

This effect hasn’t been specifically confirmed for intermittent fasting, but the pattern is the same: the starting weight on the scale isn’t a benchmark for what comes next. If you measure your progress from week four against week one, you’re comparing it to a number that won’t come around again.

In practice, that means it’s worth comparing over four weeks, not four days. The consumer advice center gives a typical rate of 500 grams to a maximum of one kilogram per week, depending on starting weight.

What else the scale measures

The only thing confirmed in the sources reviewed is the water loss at the start: the consumer advice center says that low-carb diets lead to a loss of 2 to 3 kilograms of water at first. The sources reviewed don’t say anything about other day-to-day fluctuations on the scale.

The practical takeaway still holds: Tuesday’s reading compared with Monday’s isn’t a trend. To see a change, you need weeks, not days.

What the body goes through when losing weight

The most important paragraph in this article comes from the IQWiG overview on severe overweight and explains why hitting a plateau after a few months is the rule, not the exception.

According to the report, keeping the weight off for good after losing it is usually harder than losing it in the first place. Metabolism, hormone levels, and the central nervous system are geared toward keeping the body in balance, not toward losing weight (as of 24.08.2022).

And the sentence that explains the plateau: Losing weight also reduces muscle mass, which means the body needs less energy. The more weight you lose, the harder it becomes to maintain your new weight or lose more (IQWiG, 2022).

What energy needs are made up of

IQWiG explains this in a dedicated overview. Resting energy expenditure, also called basal metabolic rate, includes the calories needed for vital bodily functions and accounts for around 70 percent of total energy needs on average. Its level depends mainly on the proportion of muscle mass in body weight (2022).

This leads to the key point taken up in Chapter 8: Sport and other activities burn calories and build muscle, and the latter increases resting energy expenditure (IQWiG, 2022).

What the evidence supports

Many disappointments arise not from the result, but from the expectation. The following figures come from the sources reviewed and refer to weight-loss programs in general, not specifically to intermittent fasting.

Evidence-based weight-loss ranges

Source: IQWiG, gesundheitsinformation.de, Weight-loss programs and medications and Severe obesity, both as of 24.08.2022. The figures refer to weight-loss programs in general.

The only figure specifically for intermittent fasting

The sources reviewed contain exactly one. The DGE reports a study in which alternate-day fasting over eight weeks led to a weight loss of around 4 percent compared with starting weight, without any change in glucose metabolism (2018).

Four percent of 90 kilograms is around 3.6 kilograms in eight weeks. That is a real result, and it is well below what most guides promise.

Why these figures should be treated with caution

Regarding the available evidence, the DGE notes that clinical human studies on the effects of intermittent fasting are still few in number and their findings are inconclusive. It also notes that no scientific studies are available on long-term effects (2018).

Another limitation is the age of the source. The most detailed German assessment dates from 2018 and reflects literature available up to 2017. That is a real limitation for a topic that has been widely discussed since then, and it belongs here rather than at the end.

What helps when progress stalls

The sources support three approaches, none of which concerns the fasting schedule.

First: food choices

The DGE identifies this as a weakness of the method itself: most intermittent fasting approaches include no recommendations, or only very vague recommendations, on food choices, so fasting alone generally does not lead to a shift toward healthier choices (2018).

This is also the biggest gap and the easiest place to start. Keeping the eating window while also changing food choices fills precisely the gap the method leaves open.

Second: exercise, including strength training

The consumer advice center notes that additional strength training is well suited to preventing unwanted muscle loss during weight loss (as of 12.08.2026). This directly targets the mechanism described in Chapter 6.

IQWiG quantifies the contribution of exercise: after twelve months, physically active participants had lost almost two kilograms more than those who only changed their diet. At the same time, studies showed that increased physical activity alone is generally not enough to lose sufficient weight (2022).

Third: duration

IQWiG advises people not to have unrealistic expectations with any diet and not to give up in disappointment if they regain some weight afterward. Those who stick with it can maintain at least some of the weight they have lost over the longer term (2022).

The greatest chances of success come from combining a diet that meets the body’s energy needs with sufficient exercise (IQWiG, 2022). Both together, not just one of them.

Fourth: feeling full

A fourth approach concerns not the amount, but the feeling of fullness. The consumer advice center explains that high-protein diets do not lead to weight loss so much by changing metabolism, but rather because people avoid high-calorie foods and feel fuller on a high-protein diet.

This is useful in the context of an eating window, because the consumer advice center explicitly lists intense hunger as a possible side effect on fasting days. However, the same source also specifies an upper limit: healthy people should keep their daily protein intake below 2 grams per kilogram of body weight over the long term.

According to the same source, people with kidney damage should avoid high-protein diets containing more than 1.3 grams per kilogram of body weight. This is one of the few explicit cautions found in the sources reviewed.

Who This Method Is Not For

The evidence is thinner than you might expect, and that needs to be said. None of the sources reviewed provides an explicit list of groups excluded specifically from intermittent fasting.

What is documented: Regarding the 5:2 approach, the Verbraucherzentrale says that headaches and difficulty concentrating may occur on fasting days, along with fatigue and intense hunger. People with diabetes and other chronic illnesses should always consult their doctor before starting.

For several days of complete fasting, which is different from intermittent fasting, the Verbraucherzentrale considers medical supervision during fasting advisable in all cases, especially for people who regularly take medication, use insulin, or have other pre-existing conditions (as of February 17, 2026).

Regarding the effects of intermittent fasting on mood, physical capacity, cognitive performance, or the risk of eating disorders, the DGE explicitly states that these cannot currently be assessed (2018). Anyone with a history in this area should therefore not start the method without consulting a doctor.

Where a test can provide guidance

If the method isn't the problem, the question remains whether it's right for you. According to the provider, the mybody®x (MYBODY Lab GmbH) saliva DNA test aims to provide some guidance. Chapter 11 states the limits of this guidance plainly, before you click.

The test includes the MY FOODBOOK with 60 recipe ideas tailored to your results. It shows how to turn a result into actual meals, rather than another list of forbidden foods.

Limitations: what a DNA test cannot do

This chapter is here because it is the only honest continuation of the previous one. The consumer advice center has a clear position on DNA-based approaches to weight loss, and it does not favor these tests.

In its overview of weight-loss programs, it lists this as a point warranting caution when investigations into the causes or individually tailored programs are based on DNA tests or stool samples. While there may be early indications that such tests could eventually provide insights, scientific research is still nowhere near advanced enough to make truly well-founded recommendations based on them. And, to quote it directly: They only make programs unnecessarily expensive (as of 12.08.2026).

On another page, the consumer advice center cites a study published in 2023, which found that a genotype-based dietary recommendation for weight loss did not work, and that weight loss after twelve weeks showed no significant difference between the groups.

This leads to a clear boundary for this article: a DNA test does not predict whether or how much you will lose weight, and this article makes no such claim at any point. What such a test can provide are pointers to guide your own choices, not a replacement for the energy balance discussed in Chapter 3 and not a shortcut.

The same source generally recommends seeking advice from qualified professionals: doctors specializing in nutrition, nutrition scientists or ecotrophologists, dietitians, and psychologists (as of 12.08.2026). This remains unchanged, even though the test is presented here.

What you can change starting tomorrow

If you take one thing away from this article, let it be this: for a week, write down what actually ends up in your eating window. Not to count, but to see whether the amount has really decreased.

The reason is in Chapter 3. If energy balance is what matters and the eating window only works indirectly by affecting opportunities to eat, then the question isn't whether you're fasting correctly, but whether it's actually making you eat less.

The second action concerns expectations. According to IQWiG's figures, five to six kilograms in six to twelve months is a normal result. Knowing that, you won't quit after eight weeks because you think it isn't working.

And a third action, if you're thinking about quitting right now: Don't change the method; change one of the eight lines in Chapter 4. Switching to the next fasting variation is the most common detour because it feels like progress but does nothing to change your energy balance.

It started with the question of why the scale stops moving during intermittent fasting. The evidence-based answer is unremarkable and, in a way, reassuring: According to the sources reviewed, the method is about as good as others, not better. What matters is the total at the end of the week.

Frequently asked questions

Sources

1. German Nutrition Society (DGE): Intermittent fasting, DGEinfo 2/2018, pages 18 to 25 – dge.de
2. Institute for Quality and Efficiency in Health Care (IQWiG): Weight-loss programs and medications, gesundheitsinformation.de (as of 24.08.2022) – gesundheitsinformation.de
3. Institute for Quality and Efficiency in Health Care (IQWiG): Severe overweight (obesity), gesundheitsinformation.de (as of 24.08.2022) – gesundheitsinformation.de
4. Institute for Quality and Efficiency in Health Care (IQWiG): Causes of obesity, gesundheitsinformation.de (as of 24.08.2022) – gesundheitsinformation.de
5. Consumer Advice Center: From metabolic diets to food combining – verbraucherzentrale.de
6. Consumer Advice Center: Weight-loss programs, what to consider when choosing one (as of 12.08.2026) – verbraucherzentrale.de
7. Consumer Advice Center: How to fast properly, tips for feeling good and sticking with it during the fasting period (as of 17.02.2026) – verbraucherzentrale.de
8. German Nutrition Society (DGE): Meal frequency and weight regulation in adults, technical information (as of July 2012) – dge.de

The description of intermittent fasting and its variations, the assessment that it is equivalent but not superior, the dropout rates of 38 and 29 percent, the estimate of around 4 percent weight loss in eight weeks, and the statements about the state of the evidence and the lack of food selection options come from source [1] and reflect the literature as of 2017. The energy balance statement, the classification of intermittent fasting, the figures of 3 to 8 and 5 to 6 kilograms, and the nearly two kilograms attributable to exercise come from [2]. The statements about regaining weight, the decline in muscle mass, and the range of 5 to 10 percent come from [3]; the explanation of resting energy expenditure and muscle mass comes from [4]. The statements about the 5:2 diet, reduced energy intake as its mechanism of action, 2 to 3 kilograms of water weight at the beginning, 500 grams to one kilogram per week, the lack of long-term studies, and the 2023 study on genotype-based recommendations come from [5]. The assessment of DNA tests as a basis for weight-loss programs, the statement about strength training, and the note on expert interpretation come from [6]. The guidance on medical supervision during fasting comes from [7]. The statements about energy balance and meal frequency come from [8] and reflect the state of knowledge in 2012. Information on price, sample type, processing time, and what is included comes from the mybody®x product page, accessed on 28.08.2026. All sources were accessed and checked on 28.08.2026.