Researchers warn that water-only fasting diets, which have become popular on social media, carry potential health risks and should only be attempted under medical supervision. A recent international study examined the effects of a 10-day water-only fast—where participants consume nothing but water—on 20 overweight volunteers. While participants lost an average of 7.7% of their body weight, many experienced side effects such as headaches, insomnia, and low blood pressure.
Contrary to the researchers’ initial hypothesis that prolonged fasting would reduce inflammation, the study found that it actually increased inflammation and stress in the body. Blood tests showed elevated levels of pro-inflammatory proteins, including C-reactive protein (CRP) and interleukin 8 (IL-8). This heightened inflammatory response raises concerns, especially for individuals with existing heart or vascular conditions, as it may increase the risk of complications.
The study also revealed some positive effects. Levels of proteins linked to muscle and bone breakdown decreased, and amyloid beta proteins associated with Alzheimer’s disease were reduced. However, these findings are preliminary, based on a small sample size, and may not apply to people with different body types or health statuses.
Experts emphasize that prolonged deprivation of food can have serious downsides. The inflammatory response observed might be a temporary adaptive mechanism, but it could also lead to lasting cardiometabolic effects after refeeding. The researchers call for further studies to understand the long-term molecular and clinical impacts of such fasting across diverse populations.
Previous research has highlighted benefits of intermittent fasting—shorter fasting periods combined with calorie control—in reducing inflammation and slowing cell aging, illustrating that fasting effects vary widely depending on the method used. There is no universal fasting strategy suitable for everyone, and any fasting regimen should be carefully managed under medical guidance.
Professor Luigi Fontana from the University of Sydney, who led the study, stated: “While the effects of water-only fasting can be dramatic, more work is needed to understand its impact on the body over longer periods. People should seek medical advice before attempting such diets, especially those with health conditions”.
In summary, water-only fasting can lead to rapid weight loss but also poses risks due to increased inflammation and stress on the body. Medical supervision is essential to minimize potential harm and to ensure safe management of any fasting regimen.
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