is Intermittent Fasting Helpful or Harmful? A Look at the Latest Research
Intermittent fasting (IF) has gained notable popularity as a weight loss strategy, but recent research challenges its purported benefits and highlights potential risks. A 2025 study, co-lead by Manuel Dote-Montero and Antonio Clavero-Jimeno at the Sport and Health University Research Institute in Spain, found that IF offers no advantage over a traditional Mediterranean diet when it comes to reducing abdominal fat, irrespective of the length of the fasting window.
The study revealed a concerning trend: participants following IF protocols experienced a loss of muscle mass. This was not observed in individuals who consumed the same number of calories consistently throughout the day. A meta-analysis examining various forms of interval fasting corroborated these findings, demonstrating a decrease in fat-free mass – essentially, muscle – across study participants.
This muscle loss is linked to protein intake. According to nutritionist Sebastian Kabisch, the body typically utilizes 20 to 40 grams of protein per meal, while adults require 70 to 90 grams daily. Concentrating this protein intake into fewer meals,as often happens with IF,can easily lead to protein deficiency. This deficiency can not onyl hinder weight loss but also contribute to muscle loss and even fat gain.
The risks associated with IF appear to increase with age. Eline Slagboom, a professor of epidemiology focused on aging research at Leiden University in the Netherlands, emphasizes that fasting signals the body to break down muscle, “That’s the last thing you need if you want to stay fit and independent in old age.” Consequently, Kabisch generally advises against IF for individuals over the age of 50.
The benefits for those without underlying health concerns are also questionable. Tinh-Hai Collet, a diabetologist, succinctly states, “If you’re healthy, you won’t benefit from intermittent fasting-you can’t improve an ideal metabolism.”
Individuals with pre-existing medical conditions require particular caution. Diabetes patients must carefully adjust medication dosage and timing under a doctor’s supervision. Similarly, those taking medication for hypertension should be aware that meal breaks can lower blood pressure.
Specific populations should avoid IF altogether. Collet advises against it for people with eating disorders and cancer, as food restriction can worsen the prognosis for cancer patients who are frequently enough already experiencing weight loss. The German Heart foundation also advises against fasting for individuals with pronounced cardiac insufficiency, recommending a maximum calorie reduction of 500 to 800 kilocalories for those with other heart conditions seeking weight loss.
Experts suggest that IF may only be advisable for healthy individuals up to middle age attempting weight loss, and even then, the positive effects are only sustained while the fasting schedule is maintained.Ultimately, a balanced diet and regular exercise remain the cornerstones of a healthy lifestyle. Intermittent fasting is not a guaranteed path to health, and for many, it may be more harmful than helpful.
(This article is based on information originally published in *Spektrum der Wissenschaft and reproduced with permission.)*
