Why am I not losing weight with intermittent fasting? The most common reasons
The essentials at a glance
The most common answer is uncomfortable and stated very clearly in the sources: intermittent fasting does not work because of the fasting itself, but because of the calories eliminated as a result. If the total amount remains the same, the scale will remain unchanged too.
IQWiG states the principle as follows: What matters when losing weight is taking in less energy than you expend (as of 24 August 2022). Regarding intermittent fasting, the DGE concludes that it is equivalent to continuous energy restriction, but not superior (2018).
You will read what the professional societies say about the method, the most common reasons for a plateau in an overview, what magnitude of weight loss has actually been demonstrated, and why your body makes it harder with every kilo you lose.
What to expect in this article
1. What intermittent fasting is and which variants exist
2. What the professional societies say about the method
3. The sentence everything hinges on
4. The most common reasons the scale stops moving
5. Why the first kilos come off quickly
6. What the body goes through when losing weight
7. What magnitude has been demonstrated
8. What helps when progress stalls
9. Who the method is not intended for
10. Where a test can provide 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 variants exist
The DGE describes intermittent fasting as a form of fasting in which food is avoided for periods of days or hours, generally with the goal of achieving long-term weight loss. Unlike other forms of fasting, it is intended to be used as a long-term eating pattern (2018).
The variants differ in the duration and frequency of abstinence. With the 5:2 diet, people eat normally on five days and consume about one quarter of their usual energy intake on two fasting days. With alternate-day fasting, fasting days with around 25 percent of the usual amount alternate with days without restrictions (DGE, 2018).
Key takeaway
The variants with fasting days explicitly reduce energy intake. The variants with eating windows, by contrast, only shorten the time. The sources do not say whether this ultimately results in lower energy intake.
The best-known variant 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 numerical designation. The DGE calls it Leangains and describes how skipping breakfast results in a fasting period of about 16 hours (2018).
IQWiG describes the same thing without using a name: eating dinner at around 8 p.m. and then not eating anything again until 12 p.m. the next day. It adds a sentence that is important for this article: No diet is necessary during the eight hours between lunch and dinner (as of August 24, 2022).
This exact sentence is often read as a free pass in many guides. It describes the method and does not say that the amount consumed during the eating window is irrelevant.
The other variants in the sources
The DGE lists several others, and the list helps put what one encounters online into context. With the 2-day diet, no more than 650 kilocalories are consumed on each of two consecutive days of the week; the food choices are supposed to be low in carbohydrates and high in protein.
With dinner cancelling, dinner is skipped on two to three days a week, creating an eating break of at least 14 hours until breakfast. With the Warrior Diet, only one meal is eaten, in the evening. The DGE also counts fasting during Ramadan as a form of intermittent fasting (2018).
What this list shows is that the term encompasses very different approaches. Anyone reading that intermittent fasting works in one way or another should therefore always check which variant is meant.
What the professional societies say about the method
This is where the answer to the question in the title appears, and it comes from several directions that all reach the same conclusion.
Documented source
“As with other diets, it is primarily the reduced energy intake that leads to weight loss.”
Consumer Advice Centre
From metabolic diets to food combining, section on the 5:2 diet
The sentence is grammatically flawed in the original and appears that way on the website. Its meaning is clear: Weight loss results from the amount of energy consumed, not from the timing pattern.
What the DGE compiled
The most comprehensive assessment comes from the German Nutrition Society and dates from 2018. Its conclusion: The available data suggested that intermittent fasting appeared to be equivalent to continuous energy restriction and had no negative side effects.
And more clearly, with reference to a meta-analysis: In terms of weight loss, fat mass, and fat-free mass, intermittent fasting is a valid but not superior alternative 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 or twelve months. The dropout rate was 38 percent for alternate-day fasting and 29 percent for daily energy restriction (DGE, 2018).
How IQWiG classifies it
IQWiG discusses intermittent fasting under the heading of what to make of diet promises and nutrition trends. So far, there have been only a few studies on it, and it is particularly unclear how successful the method is in the long term and whether it works better than other weight-loss programs. In principle, however, there is nothing to prevent trying it (as of August 24, 2022).
This is a milder formulation than a rejection, but it is not a promise of effectiveness either. The consumer advice center adds that there are still no meaningful long-term studies on the health benefits of intermittent fasting.
Where some of its good reputation comes from
Some expectations surrounding intermittent fasting are based on studies that were not conducted in humans. The DGE notes that findings from animal studies indicate that regular fasting may reduce the risk of chronic diseases (2018).
Such results are a reason for further research, not a statement about humans. IQWiG writes elsewhere in general that many studies are animal experiments with only limited relevance to humans (2022).
For you, this means that when a text about intermittent fasting argues using cellular processes or metabolic switches, it is worth looking at whom this was observed in.
The sentence everything hinges on
IQWiG puts it in one line: When losing weight, what matters is taking in less energy than you use. The composition of the diet is not decisive in this regard (as of August 24, 2022).
The DGE had already stated the same thing in 2012 in a dedicated technical briefing on meal frequency: Energy balance is what determines changes in body weight. No scientifically substantiated conclusion could be drawn about the relationship between meal frequency and weight regulation in healthy adults, which is why the DGE makes no recommendation on the subject.
What this means for your eating window
If energy balance is what determines the outcome and meal frequency has no proven role, then a shortened eating window works only indirectly: People who have fewer opportunities to eat often eat less. The DGE describes this mechanism from the opposite perspective, noting that more frequent opportunities to eat during the day also mean more frequent opportunities to consume too much energy (2012).
However, this workaround only works as long as it is not offset. Two larger meals can contain the same amount of energy as three smaller ones. This is not a guess, but the logical consequence of the sentence above, and it is why this article had to be written in the first place.
Why composition matters less than you might think
The IQWiG statement contains a second part that is often overlooked: The composition of the diet is not decisive for weight loss (2022). The Verbraucherzentrale says the same when comparing two camps and states that, for healthy people who want to lose weight, what matters is consuming fewer calories, regardless of whether it is a low-carb or low-fat diet.
This applies to quantity, not quality. A diet can balance energy intake and expenditure while still providing too few nutrients. That is why Chapter 8 puts food choices first, even though they are not decisive for the energy balance alone.
The most common reasons why the scale is not moving
The following overview organizes the reasons according to what is supported by the sources examined. It does not replace looking for causes in an individual case, but it shows where the documented explanations lie and where they do not.
| Reason | What lies behind it | Evidence |
|---|---|---|
| The amount consumed within the window | The window is shorter, but total energy intake stays the same or increases | This follows directly from IQWiG's energy-balance statement (2022) |
| No dietary change | The same foods, just at different times | The DGE states that intermittent fasting alone generally does not change food choices (2018) |
| Making up for it on eating days | With the 5:2 approach, the non-fasting days offset the fasting days | The Verbraucherzentrale writes that unrestricted feasting on days when the fast is broken does not lead to weight loss |
| The comparison with week one | Part of the rapid initial loss was water | The Verbraucherzentrale gives 2 to 3 kilograms of water as the initial loss on low-carbohydrate diets |
| Less muscle mass | Energy requirements decrease with weight | IQWiG describes exactly this relationship (2022); see Chapter 6 |
| Too little physical activity | Diet alone has limited reach | Documented magnitude: just under 2 kg difference after twelve months (IQWiG, 2022) |
| Expectations are too high | The scale is moving, just more slowly than expected | The documented magnitudes are given in Chapter 7 |
| Dropping out after a few weeks | The method is not followed through, not done incorrectly | The DGE gives a dropout rate of 38 percent for alternate-day fasting (2018) |
What stands out about this overview is that only one of the eight reasons has to do with the method itself, and even that one does not concern the fasting pattern but rather the lack of dietary changes. Six concern the amount of energy consumed, expectations, or adherence; one concerns body composition, and one concerns energy expenditure.
This is the real answer to the question in the title. People who do not lose weight with intermittent fasting are usually not doing intermittent fasting incorrectly.
Why the first kilos come off quickly
Almost every change in routine produces an initial success in the first few days that later fails to continue. The Verbraucherzentrale describes this for the start of low-carbohydrate diets: People often lose weight quickly at first, but in doing so they mainly lose 2 to 3 kilograms of water.
This effect has not been specifically documented for intermittent fasting, but the pattern is the same: The initial value on the scale is not a benchmark for what follows. Anyone who measures the trend from week four against the trend in week one is measuring against a number that will not recur in that form.
In practice, this means that comparison is worthwhile over four weeks, not four days. The Verbraucherzentrale gives a range of 500 grams to a maximum of one kilogram per week, depending on starting weight.
What else the scale measures
The only thing supported by the sources reviewed is the water loss at the beginning: The Verbraucherzentrale cites 2 to 3 kilograms of water at the start of low-carbohydrate diets. The sources reviewed say nothing about further day-to-day fluctuations on the scales.
The practical conclusion can still be drawn: A Tuesday value compared with a Monday value is not a trend. Anyone who wants to see a development needs weeks, not days.
What the body goes through when losing weight
The most important paragraph in this article comes from IQWiG’s overview of severe overweight and explains why a plateau after several months is the rule rather than the exception.
According to the source, permanently avoiding regaining weight after losing it is usually more difficult than losing the weight in the first place. Metabolism, hormone balance, and the central nervous system are geared toward keeping the body in balance, not toward losing weight (as of August 24, 2022).
And this is the sentence that explains the plateau: Weight loss also leads to a reduction in muscle mass, which means the body needs less energy. The more weight one loses, the more difficult it becomes to maintain the weight achieved or lose even more (IQWiG, 2022).
Chapter at a glance
A plateau after several months is not a sign that the method is ineffective. As weight decreases, muscle mass decreases; as muscle mass decreases, energy requirements decrease, and the same routine that initially produced a calorie deficit eventually results in energy balance. IQWiG explicitly describes this relationship as the reason why losing weight becomes more difficult with every kilogram.
What energy requirements consist of
IQWiG explains this in a separate overview. Resting energy expenditure, also called basal metabolic rate, includes the calories needed for vital bodily functions and accounts on average for about 70 percent of total calorie requirements. Its level depends mainly on the proportion of muscle mass in body weight (2022).
This leads to the lever addressed in Chapter 8: Exercise or other activities would burn calories and build muscle, and the latter would increase resting metabolic rate (IQWiG, 2022).
What range is supported by the evidence
Many disappointments arise not from the result, but from expectations. The following figures come from the reviewed sources and refer to weight-loss programs in general, not specifically to intermittent fasting.
Evidence-based ranges for weight loss
5 to 6 kg
on average in 6 to 12 months with weight-loss programs (IQWiG)
5 to 10%
of initial body weight in 6 to 12 months as the medically recommended amount (IQWiG)
2 kg
about that much more after twelve months with additional exercise (IQWiG)
Source: IQWiG, gesundheitsinformation.de, “Weight-loss programs and medications” and “Severe overweight,” both current as of August 24, 2022. The figures refer to weight-loss programs in general.
The only figure specifically for intermittent fasting
Exactly one can be found in the reviewed sources. The DGE reports a study in which alternate-day fasting over eight weeks resulted in a weight loss of around 4 percent of initial body weight, without changing glucose metabolism (2018).
Four percent of 90 kilograms is around 3.6 kilograms in eight weeks. That is a real result, and it is far below what most guides promise.
Why these figures should be read with caution
The DGE states regarding the evidence base that only a small number of clinical studies in humans on the effects of intermittent fasting had been conducted to date, and that their findings were inconclusive. It also states that no scientific studies on long-term effects were available (2018).
The age of the source also matters. The most detailed German assessment dates from 2018 and is based on literature available through 2017. For a topic that has been widely discussed since then, this is a significant limitation, and it belongs here rather than at the end.
What helps when progress stalls
The sources support three approaches, and none of them concerns the fasting schedule.
First: food choices
The DGE identifies this as a weakness of the method itself: Most intermittent-fasting concepts contain no, or only very vague, recommendations about food choices, which is why fasting alone generally does not lead to a shift toward healthier choices (2018).
This is also the biggest gap and the easiest starting point. Anyone who keeps the time window but also changes their 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 August 12, 2026). This directly targets the mechanism discussed in Chapter 6.
IQWiG quantifies the contribution of exercise: After twelve months, physically active participants had lost nearly 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 a sufficient amount of weight (2022).
Third: duration
IQWiG advises against having unrealistic expectations with any diet and against giving up in disappointment if weight subsequently increases somewhat. Those who stick with it can maintain at least part of the weight they have lost over the longer term (2022).
The chances of success are greatest with a combination of a diet that matches the body's energy needs and sufficient physical activity (IQWiG, 2022). Both together, not one or the other.
Fourth: satiety
A fourth point concerns not the amount, but the feeling. Regarding high-protein diets, the consumer advice center explains that weight loss is less a result of adapting the metabolism and more a result of avoiding high-calorie foods and feeling fuller through a high-protein diet.
This is useful in the context of an eating window because the consumer advice center explicitly identifies a strong feeling of hunger as a possible side effect on fasting days. However, the same source also gives an upper limit: For healthy people, daily protein intake should remain below 2 grams per kilogram of body weight over the long term.
According to the same source, people with damaged kidneys should avoid high-protein diets containing more than 1.3 grams per kilogram of body weight. This is one of the few explicit reservations found in the sources reviewed.
Who the method is not intended for
The evidence here is thinner than one 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 established: Regarding the 5:2 variant, the consumer advice center writes that headaches and difficulty concentrating may occur on fasting days, along with fatigue and a strong feeling of hunger. People with diabetes and others with chronic illnesses should definitely consult their doctor before starting.
For multi-day complete fasting—meaning something other than intermittent fasting—the consumer advice center always considers medical supervision during fasting advisable, 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 resilience, 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 begin the method without consulting a doctor.
People who do not lose weight with intermittent fasting are usually not doing intermittent fasting incorrectly.
Where a test can provide indications
If the method is not the problem, the question of personal suitability remains. According to the provider, a saliva-based DNA test from mybody®x (MYBODY Lab GmbH) aims to provide indications in this regard. Chapter 11 states the limits of these indications plainly, before you click.
DNA test from saliva
DNA Metabolism Analysis | incl. 28-day plan & recipe book
According to the product page, it provides insights into genetic foundations and helps identify foods that fit your daily routine. The product page makes no statement about how much weight you will lose. The test does not provide a diagnosis or predict weight-loss success.
Laboratory analysis 15–25 business days after sample receipt
Product page information, accessed 28 August 2026
The test includes the MY FOODBOOK with 60 recipe ideas tailored to your personal analysis. It shows how a result becomes concrete meals instead of another list of forbidden foods.
Limitations: what a DNA test cannot do
This chapter appears here because it is the only honest continuation of the previous one. The consumer advice center takes a clear position on DNA-based approaches to weight loss, and it does not support such tests.
In its overview of weight-loss programs, it lists this as a point warranting caution when research into the causes or the individually tailored program is based on DNA tests or stool samples. Although there are initial indications that such tests may one day allow conclusions to be drawn, scientific research is currently still far from being advanced enough for truly well-founded recommendations to be made on the basis of these tests. It continues, in the original wording: They only make programs unnecessarily more expensive (as of 12 August 2026).
On another page, the consumer advice center refers to a study published in 2023, according to which a genotype-based dietary recommendation for weight reduction did not work and weight loss after twelve weeks showed no significant difference between the groups.
This leads to an unequivocal 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 anywhere. What such a test can provide are indications to help you make your own choices—not a substitute for the energy balance discussed in Chapter 3 and not a shortcut.
The same source generally advises seeking guidance from qualified professionals: doctors specializing in nutrition, nutrition scientists or ecotrophologists, dietitians, and psychologists (as of August 12, 2026). This remains unchanged even though the test is presented here.
What you can change starting tomorrow
If you take away just one action from this article, let it be this: For one 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 given in Chapter 3. If the energy balance is decisive and the eating window works only indirectly by affecting opportunities to eat, then the question is not whether you are fasting correctly, but whether it leads to eating less for you at all.
The second step concerns expectations. Five to six kilograms over six to twelve months is a normal result according to IQWiG's figures. Anyone who knows this will not give up after eight weeks because they think it is not working.
And a third step, if you are currently considering giving up: Do not change the method; change one of the eight lines from Chapter 4 instead. Switching to the next fasting variation is the most common detour because it feels like progress while changing nothing about the energy balance.
The starting question was why the scales stop moving during intermittent fasting. The evidence-based answer is unremarkable and reassuring in a way: According to the sources reviewed, the method is about as effective as other methods, and no better. What matters is what adds up at the end of the week.
Frequently asked questions
Why am I not losing weight with intermittent fasting?
The most common reason is that the total energy intake has remained the same. IQWiG notes that the decisive factor in losing weight is consuming less energy than you expend (as of August 24, 2022). The consumer advice center puts it this way for intermittent fasting: as with other diets, weight-loss success is primarily caused by reduced energy intake. A shorter eating window only reduces the amount consumed if it is not compensated for elsewhere.
Is intermittent fasting better than other diets?
Not according to the sources reviewed. The DGE concludes that intermittent fasting is a valid alternative, but not superior to continuous energy restriction (2018). IQWiG states that it is above all unclear how successful the method is in the long term and whether it works better than other weight-loss programs, but that there is nothing to prevent trying it (as of August 24, 2022).
How much weight can I realistically lose?
IQWiG generally gives around 3 to 8 kilograms within 6 to 12 months for weight-loss programs, with an average of around 5 to 6 kilograms, and doctors recommend losing 5 to 10 percent of body weight within 6 to 12 months, depending on starting weight (as of 24 August 2022). Specifically for intermittent fasting, the DGE cites a study showing around 4 percent weight loss over eight weeks with alternate-day fasting (2018).
Why does losing weight become more difficult over time?
IQWiG describes the connection as follows: Weight loss also leads to a reduction in muscle mass, so the body needs less energy. The more weight you lose, the harder it becomes to maintain the weight you have reached or lose more (as of 24 August 2022). According to the same source, resting energy expenditure depends primarily on the proportion of muscle mass and accounts for an average of about 70 percent of calorie requirements.
Can a DNA test help with weight loss?
Not a prediction. The consumer advice center lists DNA tests as a basis for weight-loss programs among the areas requiring caution: As of now, scientific research is nowhere near advanced enough for such tests to provide truly well-founded recommendations; they only unnecessarily make programs more expensive (as of 12 August 2026). It also refers to a 2023 study according to which a genotype-based dietary recommendation for weight loss did not work. Anyone taking such a test should have the results professionally interpreted.
Next step
Guidance for making your own choices
If you want to know which foods fit your everyday life, the test provides some guidance. It does not predict weight-loss success and does not replace nutritional counseling. The assessment from Chapter 11 remains unchanged.
View DNA Metabolism Analysis Low Carb for BeginnersRead more
You might also be interested in this
The same range of 5 to 10 percent, this time for a method with a list of foods to avoid.
Relevant to muscle preservation from Chapters 6 and 8.
Sources
- German Nutrition Society (DGE): Intermittent fasting, DGEinfo 2/2018, pages 18 to 25 – dge.de
- Institute for Quality and Efficiency in Health Care (IQWiG): Weight-loss programs and medications, gesundheitsinformation.de (as of 24 August 2022) – gesundheitsinformation.de
- Institute for Quality and Efficiency in Health Care (IQWiG): Severe overweight (obesity), gesundheitsinformation.de (as of 24 August 2022) – gesundheitsinformation.de
- Institute for Quality and Efficiency in Health Care (IQWiG): Causes of obesity, gesundheitsinformation.de (as of 24 August 2022) – gesundheitsinformation.de
- Consumer Advice Centre: From metabolic diets to food combining – verbraucherzentrale.de
- Consumer Advice Centre: Weight-loss programs: what to consider when choosing one (as of 12/08/2026) – verbraucherzentrale.de
- Consumer Advice Centre: How to fast properly, tips for feeling good and sticking with it during the fasting period (as of 17/02/2026) – verbraucherzentrale.de
- 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 variants, the assessment that it is equivalent rather than superior, the dropout rates of 38 and 29 percent, the figure of around 4 percent weight loss over eight weeks, the statements about the evidence and the lack of food selection, come from source [1] and reflect the state of the literature in 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 metabolic rate and muscle mass comes from [4]. The statements about the 5:2 diet, reduced energy intake as the mechanism of action, 2 to 3 kilograms of water at the beginning, 500 grams to 1 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 professional classification come from [6]. The advice 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 scope of delivery comes from the mybody®x product page, accessed on 28/08/2026. All sources were accessed and reviewed on 28/08/2026.
mybody®x editorial & expert team
Nutritional science Laboratory diagnostics Blood analysis interpretation Nutrigenetics
This article was created by the mybody®x editorial and expert team. The team combines laboratory diagnostics, nutritional science, and the interpretation of blood analyses. Those who contribute to it are listed on the authors’ page.
Published on 28/08/2026 · Last updated on 28/08/2026
The content is intended for general information and does not replace medical advice, diagnosis, or treatment. Reference ranges depend on the laboratory, method, and age—the information on your test report is always authoritative.
Share now:
What boosts fat burning? The levers, honestly assessed
Regeneration: What your body really needs after training, stress, and during sleep