How well does intermittent fasting help you lose weight?
"...the current evidence does not justify the enthusiasm that can be observed in the social media."
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Intermittent fasting has been very trendy for some time now - especially in social media: it is said to reduce weight and have a positive effect on metabolism. A recently published Cochrane Review examines the question: How much do adults who are overweight or obese lose weight through intermittent fasting? In simple terms, it shows that they may not lose more weight with intermittent fasting than with other diets - but probably slightly more than without targeted nutritional intervention.
"Intermittent fasting may be a sensible option for some people," says Luis Garegnani, one of the review authors and director of the Cochrane Center at the Universidad Hospital Italiano de Buenos Aires. "But the current evidence does not justify the enthusiasm that can be observed on social media."
The new review summarizes different forms of intermittent fasting and shows, based on the evaluation of 21 randomized controlled trials with a total of 1430 participants Compared to other diets, intermittent fasting may not reduce body weight in people who are overweight or obese, or only minimally.
The wording "possibly" is important from a scientific point of view because this review result is subject to a relatively high degree of uncertainty. The review authors rate its reliability as "low" - this is the second lowest of four possible levels in the so-called GRADE system, which is used to assess the reliability of scientific findings. Many of the studies evaluated were small and had methodological flaws. In other words, new study results could well lead to the evidence on intermittent fasting changing.
The review authors not only compared intermittent fasting with other diets, but also with "no structured dietary intervention". (In simple terms, this means: no diet or largely maintaining one's own eating habits). Six studies with 427 overweight or obese participants were analyzed. This probably shows a small effect: Intermittent fasting probably reduces body weight by an average of 3.4 percent more than people without a targeted nutritional intervention. The review authors classify the reliability of these figures as "moderate". (This corresponds to the second highest of four levels in the GRADE system.) From a scientific perspective, this second review result is therefore also subject to a certain but lower level of uncertainty.
An intermittent fasting person with a body weight of 100 kilos would therefore probably lose around 3.4 kilos more on average than someone who is not actively intermittent fasting. However, clinical guidelines recommend a weight loss of at least five percent for people who are overweight or obese, as health risks only decrease above this threshold.
Prof. Dr. Jörg Meerpohl, Scientific Director of Cochrane Germany in Freiburg, explains that the current review is limited by the fact that almost all of the studies evaluated were only conducted over a period of six to twelve months. "Based on the available evidence, it is not possible to make a reliable statement as to whether overweight and obese people succeed in reducing their weight so significantly in the long term with intermittent fasting that they become healthier as a result," says Meerpohl. "There is also a lack of data on how satisfied people are with intermittent fasting, whether they can sustain it well in everyday life in the medium and long term and whether it has any undesirable effects. It also remains unclear what effect intermittent fasting has on concomitant obesity-related illnesses and whether it helps to prevent type 2 diabetes, for example. There is also a lack of data on this so far."
The studies included in the Cochrane Review mainly investigated the following forms of intermittent fasting:
- Time-restricted feeding: Daily food intake is restricted to a fixed time window, usually to a maximum of 8 to 10 hours per day. The rest of the time is spent fasting, often overnight for at least 14 hours.
- Periodic fasting: One or two days a week are spent fasting or hardly eating at all. The remaining five to six days are spent eating normally.
- Alternate-day fasting: Fasting days and days with normal food intake alternate. On fasting days, either nothing or very little is eaten.
- Modified alternate-day fasting (e.g. 5:2 diet): Calorie intake is greatly reduced on two days per week, while eating normally on the other five days. Food is not completely avoided on the fasting days.
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
Original publication
Luis I Garegnani, Gisela Oltra, Diego Ivaldi, Mariana Andrea Burgos, Paola J Andrenacci, Sabrina Rico, Melinda Boyd, Diane Radler, Camila Micaela Escobar Liquitay, Eva Madrid; "Intermittent fasting for adults with overweight or obesity"; Cochrane Database of Systematic Reviews, Volume 2026, 2026-2-16
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