The advice to try a fasting diet that uses only water may be filling your social media feed, but due to potential negative effects, researchers are warning people to seek medical advice before starting these diets.
A team of international researchers published a new study that analyzed the effects of a 10-day 10-day drinking diet on 20 people (so there is no drink other than water). Participants lost an average of 7.7% of their weight, but also experienced side effects, including headache, insomnia, and hypotension.
Overall, fasting appears to increase inflammation and put more stress on the body, which can lead to health complications, especially for patients with heart or vascular conditions.
“Our hypothesis is that prolonged water reduces inflammation in the body,” said Luigi Fontana, a physician scientist at the University of Sydney.
“However, we found the opposite to this is correct – prolonging fasting can put stress on the body and increase the amount of pro-inflammatory protein in the blood, which may increase the risk of health problems for people with heart and blood vessel conditions.”
The researchers analyzed how fasting affects plasma proteins in the body. (Comsissati et al., Molecular metabolism2025)
The main way researchers measure the effects of fasting on the body is through protein levels. Many proteins associated with inflammation, including C-reactive protein (CRP) and interleukin 8 (IL-8), became more abundant in the blood plasma of the participants.
Other effects were also seen: the levels of proteins associated with breaking down muscle and bones were reduced, and amyloid beta protein was closely associated with the development of Alzheimer’s disease.
However, the evidence remains relatively uncertain. These are just a preliminary discovery from a small group of people, all of whom classify them as being overweight. The effects may vary in people with larger sample sizes or body types.
For a long time, there seem to be very serious disadvantages to deprive the body of food – which means that medical advice should always be sought before starting this diet.
“While acute inflammatory response during prolonged fasting may be a transient adaptation mechanism, it raises concerns about the underlying cardiac metabolic effects,” the researchers wrote in a published paper.
“Further research is necessary to elucidate the long-term molecular and clinical implications of prolonged fasting in different populations.”
The team noted previous research highlighting the potential benefits of intermittent fasting in slowing cellular aging, reducing inflammation (as opposed to what is seen here), and reducing disease risk, so this is a complex situation.
In recent years, intermittent fasting has been paid more attention to than prolonged fasting. It seems that intermittent fasting must be combined with calorie control in order to see any benefits when it comes to weight loss, and some disadvantages need to be considered.
It seems clear that there is no strategy for a certain size when fasting – any attempt to lose weight by turning off the body’s food and energy supply requires careful management.
“People are looking for effective ways to manage their weight, and while the fasting effect of only water can be dramatic, more work needs to be done to understand the effects of these diets on the body,” Fontana said.
The study has been published in Molecular metabolism.
