Diet and nutritionFasting — a way to improve health or a dangerous fad?
Sources: 16 · Article: 18 429 characters
Fasting may support health and metabolism, but there is no basis for considering it beneficial for everyone.
- Prof. David Ludwig notes that long-term evidence is very limited and that people differ in how well they tolerate fasting.
- Prof. David Ludwig warns that prolonged calorie restriction may increase hunger and slow metabolism; Ewa Dąbrowska also points to the risk of an acute porphyria attack in people who are predisposed.
What the authors write
Bracia Rodzeń
Healthy fasting means voluntarily and willingly not eating for a set period of time to achieve health benefits.
„Healthy fasting means voluntarily and willingly not eating for a set period of time to achieve specific health benefits. Fasts differ in length and in which drinks are allowed during the fast—water, tea, coffee, and broth.
Fasting is simply any period when you do not eat.”Post zdrowy to dobrowolne, niewymuszone niejedzenie przez określony okres czasu, celem osiągnięcia określonych korzyści zdrowotnych. Posty różnią się długością trwania oraz dozwolonymi produktami do picia w trakcie – woda, herbata, kawa, rosół.
Post to tak naprawdę każdy okres, w którym nie jesz.
Bracia Rodzeń
Intermittent fasting 16/8 means going 16 hours without eating and having 8 hours for meals.
„A day has 24 hours. Divide it into 8 hours when you eat and the remaining 16 hours when you fast—that is, 16 hours without eating, or #healthyNOTeating. These 8 hours are called the eating window. During these 8 hours, when you eat your meals, you decide and adjust your eating window to fit your life, work, and responsibilities.”Doba ma 24 godziny, podziel ją na 8 godzin, w trakcie których jesz i pozostałe 16 godzin, podczas których pościsz,czyli jest to 16 godzin niejedzenia, #zdrowegoNIEjedzenia. Te 8 godzin nazywamy okienkiem żywieniowym. W ciągu tych 8 godzin, w których jesz posiłki, to właśnie Ty decydujesz i dostosowujesz sobie okienko żywieniowe do życia, pracy i obowiązków, które masz.
Ewa Dąbrowska
Ewa Dąbrowska links fasting to lower insulin levels, weight loss, and a reduction in visceral fat, which she says can limit the causes of metabolic disorders.
„During fasting, insulin levels fall, triggering processes that reduce body weight and reverse metabolic diseases. Abdominal obesity is particularly dangerous: visceral fat acts like a gland that releases pro-inflammatory substances (adipokines), which contribute to insulin resistance and inflammation. Fasting reduces visceral fat, curbing adipokine production and thereby eliminating one of the main causes of metabolic disorders.”W czasie postu poziom insuliny spada, co uruchamia procesy redukcji masy ciała i cofania się chorób metabolicznych. Szczególnie groźna jest otyłość brzuszna – tłuszcz trzewny działa jak gruczoł wydzielający substancje prozapalne (adipokiny), które sprzyjają rozwojowi insulinooporności i stanów zapalnych. Post redukuje tłuszcz trzewny, hamując produkcję adipokin, i w ten sposób eliminuje jedną z głównych przyczyn zaburzeń metabolicznych.
Ewa Dąbrowska
According to Ewa Dąbrowska, fasting reduces excess body fat and fatty liver and improves the sensitivity of cells to insulin.
„Fasting helps reduce excess body fat and reverse fatty liver. As a result, cells become more sensitive to insulin. This is crucial because insulin resistance is at the root of many metabolic diseases: type 2 diabetes, atherosclerosis, high blood pressure, lipid disorders, and gout.”Post wspomaga redukcję nadmiaru tkanki tłuszczowej i cofa stłuszczenie wątroby. W efekcie poprawia się wrażliwość komórek na insulinę, co jest kluczowe, ponieważ insulinooporność leży u podstaw wielu chorób metabolicznych: cukrzycy typu 2, miażdżycy, nadciśnienia, zaburzeń lipidowych czy dny moczanowej.
Ewa Dąbrowska
Ewa Dąbrowska describes reversing insulin resistance as one of the most important effects of fasting and links it to metabolic diseases.
„One of the most important effects of fasting is reversing insulin resistance—the main cause of obesity, type 2 diabetes, fatty liver, atherosclerosis, and other metabolic diseases.
A common effect during the treatment is a surge in energy, improved physical fitness, and better heart function.”Jednym z najważniejszych efektów postu jest odwracanie insulinooporności – głównej przyczyny otyłości, cukrzycy typu 2, stłuszczenia wątroby, miażdżycy i innych chorób metabolicznych.
W trakcie kuracji częstym objawem jest przypływ energii, poprawa wydolności fizycznej i pracy serca.
Ewa Dąbrowska
Ewa Dąbrowska presents short, periodic fasts as a way that may support health and help prevent chronic diseases.
„Even short, periodic fasts help cleanse the body of toxins, provide bioactive plant compounds and trace minerals, and restore the body’s physiological balance. Regular fasting may help prevent many chronic diseases.”Nawet krótkie, okresowe posty pomagają oczyszczać organizm z toksyn, dostarczać bioaktywnych związków roślinnych i mikroelementów, a także przywracać fizjologiczną równowagę organizmu. Regularnie praktykowany post może zapobiegać wielu chorobom przewlekłym.
Ewa Dąbrowska
Ewa Dąbrowska links fasting to possible health improvements in people with certain diseases and to a stronger immune system.
„It has been observed that people with diabetes, atherosclerosis, peptic ulcer disease, or collagen diseases who adopt a healthy plant-based diet and fast often experience an improvement in their health. Fasting may also help treat infertility.
One of the key effects of fasting is strengthening the immune system. Infections, colds, and tonsillitis then disappear, while sleep quality, concentration, and memory improve.”Zaobserwowano, że osoby z cukrzycą, miażdżycą, chorobą wrzodową czy kolagenozami, które przechodzą na zdrową dietę roślinną i stosują posty, często doświadczają poprawy stanu zdrowia. Post może również wspomagać leczenie niepłodności.
Jednym z kluczowych efektów postu jest wzmocnienie układu odpornościowego, wtedy znikają infekcje, przeziębienia, anginy, poprawia się jakość snu, koncentracja, pamięć.
Ewa Dąbrowska
Ewa Dąbrowska attributes possible benefits for physical and mental health, as well as disease prevention, to regular fruit-and-vegetable fasts.
„Supporting health
Regular fruit-and-vegetable fasts can effectively help cleanse the body and support health, both physical and mental. Although fasting is most often associated with treatment, it is above all an effective method of prevention.”Wzmacnianie zdrowiaRegularne stosowanie postów warzywno-owocowych może skutecznie wspierać oczyszczanie organizmu i wzmacniać zdrowie, zarówno ciała, jak i ducha. Post, choć najczęściej kojarzony z leczeniem, jest przede wszystkim skuteczną metodą profilaktyki.
Ewa Dąbrowska
Ewa Dąbrowska says that fasting may reduce inflammation, pain, and swelling and improve joint mobility in rheumatoid arthritis, especially in its early stages.
„Fasting may reduce inflammation, pain, and swelling and improve joint mobility—especially in the early stages of the disease. It is important to rule out food intolerances (most often involving milk, eggs, grains, and yeast).
Systemic lupus erythematosus
Antibodies attack cell nuclei (ANA).”Post może zmniejszyć stan zapalny, ból i obrzęki oraz poprawić ruchomość stawów – szczególnie w początkowym stadium choroby. Ważne jest wykluczenie nietolerancji pokarmowych (najczęściej dotyczą one: mleka, jaj, zbóż i drożdży).
Toczeń rumieniowaty układowy
Przeciwciała atakują jądra komórek (ANA).
Ewa Dąbrowska
Ewa Dąbrowska presents a cleansing fast as a way to detoxify the body and a fruit-and-vegetable diet as a modified version of it.
„The most effective and also the most natural way to rid the body of toxins proved to be a cleansing fast[iii], or its modified version—a fruit-and-vegetable diet[iv]. We have already had more than a decade of experience with the vegetable diet.”Najskuteczniejszą i zarazem najbardziej naturalną metodą odtruwania organizmu z toksyn okazała się oczyszczająca głodówka[iii], lub jej modyfikacja – dieta warzywno – owocowa[iv]. Ze stosowaniem diety warzywnej posiadamy już kilkunastoletnie doświadczenie.
Ewa Dąbrowska
Ewa Dąbrowska states that fasting can trigger an acute intermittent porphyria attack in people with a genetic predisposition.
„A deficiency of protoporphyrinogen can lead to an acute porphyria attack, but only in people who are genetically predisposed. In rats, fasting increased porphyrin excretion 23, whereas in patients with PCT we observed a decrease; the improvement was proportional to the duration of treatment.”Niedobór protoporfirynogenu może prowadzić do napadu ostrej porfirii, ale tylko u osób predysponowanych genetycznie. U szczurów głodówka zwiększała wydalanie porfiryn 23, natomiast u pacjentów z PCT obserwowaliśmy jego obniżenie; poprawa była proporcjonalna do czasu trwania kuracji.
Ewa Dąbrowska
Ewa Dąbrowska reports that a very-low-energy fruit-and-vegetable diet improved selected biochemical measures in people with porphyria cutanea tarda.
„Conclusions: In patients with porphyria cutanea tarda, a very-low-energy fruit-and-vegetable diet had a beneficial effect on selected biochemical measures. Given its clinical and economic benefits, its use in treating PCT is worth considering.”Wnioski: W grupie chorych z porfirią późną skórną dieta warzywno-owocowa o bardzo niskiej wartości energetycznej korzystnie wpłynęła na wybrane parametry biochemiczne. Ze względu na korzyści kliniczne i ekonomiczne warto rozważyć jej zastosowanie w leczeniu PCT.
Ewa Dąbrowska
Ewa Dąbrowska notes that fasting can trigger an acute intermittent porphyria attack, although in the described cases of PCT, a VLED diet reduced porphyrin excretion.
„Calorie restriction also affects porphyrin metabolism: fasting can trigger an acute intermittent porphyria attack (Welland 35, Smith 32), but in rats and our patients with PCT, a VLED reduced porphyrin excretion and accelerated the healing of skin lesions.”Restrykcje kaloryczne wpływają też na metabolizm porfiryn: głodówka może wywołać atak ostrej przerywanej porfirii (Welland 35, Smith 32), lecz u szczurów i naszych pacjentów z PCT VLED zmniejszyło wydalanie porfiryn i przyspieszyło gojenie zmian skórnych.
Nathan S. Bryan
Nathan S. Bryan presents fasting as a possible way to lose weight, improve insulin sensitivity, blood sugar control, and cholesterol levels, and reduce inflammation.
„Fasting has been shown to improve the following:
Weight loss: Fasting reduces calorie intake, which can lead to weight loss.
Improved metabolic health: Fasting can improve insulin sensitivity, blood sugar control, and cholesterol levels.
Reduced inflammation: Fasting may reduce inflammation throughout the body.”Fasting has been shown to improve the following:
Weight loss: Fasting reduces calorie intake, which can lead to weight loss.
Improved metabolic health: Fasting can improve insulin sensitivity, blood sugar control, and cholesterol levels.
Reduced inflammation: Fasting may reduce inflammation throughout the body.
Nathan S. Bryan
Nathan S. Bryan presents fasting as safe and effective, and also mentions the emotional and spiritual benefits associated with fasting during Lent.
„It is safe, it is cheap (actually it is cost saving when you are not buying food) and it is very effective. In fact, there is not a single medication that can do all the things that fasting has been proven to do.
Fasting has been shown to improve the following:
Weight loss: Fasting reduces calorie intake, which can lead to weight loss.”It is safe, it is cheap (actually it is cost saving when you are not buying food) and it is very effective. In fact, there is not a single medication that can do all the things that fasting has been proven to do.
Fasting has been shown to improve the following:
Weight loss: Fasting reduces calorie intake, which can lead to weight loss.
prof. David Ludwig
Prof. David Ludwig allows that intermittent fasting may have metabolic benefits, including improved insulin sensitivity, but emphasizes the limited long-term evidence and differences in how well people tolerate it.
„For those who can tolerate it, intermittent fasting may provide significant metabolic benefits, such as improved insulin sensitivity. In addition, fasting results in the production of ketones, considered by some a sort of superfuel for brain and body. Of course, intermittent fasting can also save time, since you’ll make fewer meals.
However, the evidence basis to support intermittent fasting is very limited, with virtually no long-term trials. And people differ greatly in their ability to tolerate fasting, so it’s critical to pay attention to your body’s responses.”For those who can tolerate it, intermittent fasting may provide significant metabolic benefits, such as improved insulin sensitivity. In addition, fasting results in the production of ketones, considered by some a sort of superfuel for brain and body. Of course, intermittent fasting can also save time, since you’ll make fewer meals.
However, the evidence basis to support intermittent fasting is very limited, with virtually no long-term trials. And people differ greatly in their ability to tolerate fasting, so it’s critical to pay attention to your body’s responses.
prof. David Ludwig
Prof. David Ludwig describes a study in which people who ate a few larger meals had worse lipid and glucose results and produced more stress hormones than people who ate many small meals.
„In a classic feeding study, volunteers were given the same calories either as many small meals (Nibbling) or as a few big meals (Gorging) each day. The Nibbling group showed better blood lipid and glucose levels, and lower stress hormone production. So at least under some conditions (especially, a high carbohydrate diet), restricting calorie intake to just a few hours a day can have negative effects.”In a classic feeding study, volunteers were given the same calories either as many small meals (Nibbling) or as a few big meals (Gorging) each day. The Nibbling group showed better blood lipid and glucose levels, and lower stress hormone production. So at least under some conditions (especially, a high carbohydrate diet), restricting calorie intake to just a few hours a day can have negative effects.
prof. David Ludwig
Prof. David Ludwig notes that restricting eating to a few hours may have negative effects under certain conditions, especially with a high-carbohydrate diet.
„The Nibbling group showed better blood lipid and glucose levels, and lower stress hormone production. So at least under some conditions (especially, a high carbohydrate diet), restricting calorie intake to just a few hours a day can have negative effects.”The Nibbling group showed better blood lipid and glucose levels, and lower stress hormone production. So at least under some conditions (especially, a high carbohydrate diet), restricting calorie intake to just a few hours a day can have negative effects.
prof. David Ludwig
Prof. David Ludwig warns that restricting calories for longer periods may increase hunger and slow metabolism.
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The problem is what happens later, after the first few weeks or months. Your body is going to start fighting back with increasing hunger, slowing metabolism. If you keep cutting back calories you only make that situation worse.”Trending: Best Happiness Books of 2025 (So Far)
The problem is what happens later, after the first few weeks or months. Your body is going to start fighting back with increasing hunger, slowing metabolism. If you keep cutting back calories you only make that situation worse.
prof. David Ludwig
Prof. David Ludwig emphasizes that short-term weight loss after calorie restriction does not determine later success, and that the body’s response also depends on the type of food.
„Yes you lose the same weight on 1,000 calories of junk food versus 1,000 calories of high nutrition. But you’ll be feeling entirely differently. Your metabolic state will be different and the likelihood that you’ll succeed for the next two months, let alone the rest of your life, will be dramatically different.”Yes you lose the same weight on 1,000 calories of junk food versus 1,000 calories of high nutrition. But you’ll be feeling entirely differently. Your metabolic state will be different and the likelihood that you’ll succeed for the next two months, let alone the rest of your life, will be dramatically different.
Research from PubMed · Europe PMC
We selected 3 studies with the best, positive results. This is a selection, not a full review of all research.
Total number of studies on this topic in PubMed: 129 513.
A review found that various forms of intermittent fasting reduced body weight compared with unrestricted eating.
Aim of the study: To assess the effect of intermittent fasting diets, with continuous energy restriction or unrestricted (ad-libitum) diets on intermediate cardiometabolic outcomes from randomised clinical trials.
Results: 99 randomised clinical trials involving 6582 adults of varying health conditions (720 healthy, 5862 existing health conditions) were identified. All intermittent fasting and continuous energy restriction diet strategies reduced body weight when compared with ad-libitum diet. Compared with continuous energy restriction, alternate day fasting was the only form of intermittent fasting diet strategy to show benefit in body weight reduction (mean difference -1.29 kg (95% CI -1.99 to -0.59), moderate certainty of evidence). Additionally, alternate day fasting showed a trivial reduction in body weight compared with both time restricted eating and whole day fasting (mean difference -1.69 kg (-2.49 to -0.88) and -1.05 kg (-1.90 to -0.19), respectively, both with moderate certainty of evidence).
Money for the studycompany together with others · The Diabetes and Nutrition Study Group (DNSG) of the European Association of the Study of Diabetes (EASD), Canadian Institutes of Health Research, Canada Foundation for Innovation (CFI)
Do the authors have ties to companies?yes — the authors reported it
Did a manufacturer help with the study?YES
Type of studycombined analysis of many studies (meta-analysis)
Participants6 582
“Not stated” does not mean nobody paid — the database does not always record it.
In people with obesity, fasting and calorie restriction supported weight loss, while fasting also improved insulin sensitivity markers in the short term.
Aim of the study: fasting-based strategies (FBS) and continuous caloric restriction (CCR) are popular methods for weight loss and improving metabolic health. FBS alternates between eating and fasting periods, while CCR reduces daily calorie intake consistently. Both aim to create a calorie deficit, but it is still uncertain as to which is more effective for short- and long-term weight and metabolic outcomes.
Results: both interventions led to weight loss, with a reduction of 5.5 to 6.5 kg observed at the six-month mark. However, the results showed that FBS led to slightly greater short-term reductions in body weight (-0.94 kg, p = 0.004) and fat mass (-1.08 kg, p = 0.0001) compared to CCR, although these differences are not clinically significant. Both interventions had similar effects on lean mass, waist and hip circumference, blood pressure, lipid profiles, and glucose metabolism. However, FBS improved insulin sensitivity, with significant reductions in fasting insulin (-7.46 pmol/L, p = 0.02) and HOMA-IR (-0.14, p = 0.02). despite these short-term benefits, FBS did not show superior long-term outcomes compared to CCR. Both strategies are effective for weight management, but more research is needed to explore the long-term clinical relevance of FBS in obese populations.
Money for the studynot stated
Do the authors have ties to companies?no — the authors say so
Did a manufacturer help with the study?NO
Type of studycombined analysis of many studies (meta-analysis)
“Not stated” does not mean nobody paid — the database does not always record it.
The review describes metabolic benefits associated with intermittent fasting and time-restricted eating.
Aim of the study: We have long known that subjects with obesity who fast for several weeks survive. Calculations that assume the brain can only use glucose indicated that all carbohydrate and protein sources would be consumed by the brain within several weeks yet subjects with obesity who fasted for several weeks survived.
Results: Intermittent fasting and its variants such as time-restricted eating are fasting models that are far less regimented than starvation and severe calorie restriction; yet they produce metabolic benefits. The mechanisms that produce the metabolic changes that intermittent fasting elicits are relatively unknown. In this article, we review the physiology of starvation, starvation adaptation diets, diet-induced ketosis, and intermittent fasting. Understanding the premise and physiology that these regimens induce is necessary to draw parallels and provoke thoughts on the mechanisms underlying the metabolic benefits of intermittent fasting and its variants.
Money for the studygovernment, public institutions · NIA NIH HHS, NIGMS NIH HHS
Do the authors have ties to companies?not stated
Did a manufacturer help with the study?unknown
Type of studydiscussion of other studies
“Not stated” does not mean nobody paid — the database does not always record it.
Perspectives and opinion materials
The content below presents the authors’ opinions, interpretations and hypotheses. It is not treated as equal to scientific studies and systematic reviews.
Orthomolecular Medicine News Service Opinion material
„5.2 Intermittent Fasting Improves Vitamin D Resistance Recent studies indicate that intermittent fasting and prolonged fasting can improve vitamin D levels and its metabolism, particularly in individuals with various health conditions. Effects of Prolonged Fasting on Vitamin D: Both intermittent and prolonged fasting have shown promise in enhancing vitamin D levels and may serve as beneficial strategies in managing vitamin D resistance and related health conditions.”5.2 Intermittent Fasting Improves Vitamin D Resistance Recent studies indicate that intermittent fasting and prolonged fasting can improve vitamin D levels and its metabolism, particularly in individuals with various health conditions. Effects of Prolonged Fasting on Vitamin D: Both intermittent and prolonged fasting have shown promise in enhancing vitamin D levels and may serve as beneficial strategies in managing vitamin D resistance and related health conditions.
Orthomolecular Medicine News Service Opinion material
„Intermittent fasting for metabolic diseases Intermittent fasting has been shown to have a range of potential benefits for metabolic health. It can improve metabolic and inflammatory parameters, particularly when combined with regular physical exercise (Zhang 2023). Different intermittent fasting approaches, such as alternate day fasting and time-restricted eating, have been found to be effective in weight loss and improving cardiometabolic risk factors (Zhu 2020). Aligning food habits with the circadian clock through early time-restricted feeding can also improve metabolic health (Charlot 2021).”Intermittent fasting for metabolic diseases Intermittent fasting has been shown to have a range of potential benefits for metabolic health. It can improve metabolic and inflammatory parameters, particularly when combined with regular physical exercise (Zhang 2023). Different intermittent fasting approaches, such as alternate day fasting and time-restricted eating, have been found to be effective in weight loss and improving cardiometabolic risk factors (Zhu 2020). Aligning food habits with the circadian clock through early time-restricted feeding can also improve metabolic health (Charlot 2021).
Orthomolecular Medicine News Service Opinion material
„Fasting also lowers inflammation, improves insulin sensitivity, and promotes metabolic flexibility [39-41]. Exercise Endurance Benefits: Both ketogenic metabolism and intermittent fasting increase reliance on fat oxidation, sparing glycogen and reducing lactate buildup.”Fasting also lowers inflammation, improves insulin sensitivity, and promotes metabolic flexibility [39-41]. Exercise Endurance Benefits: Both ketogenic metabolism and intermittent fasting increase reliance on fat oxidation, sparing glycogen and reducing lactate buildup.
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