Water fasting—a practice of abstaining from all food and beverages except water—has become a notable health trend in the U.S. in recent years. While fasting has a long history in religious and spiritual practices, today, many people try it for purported health benefits, such as weight loss, reduced inflammation, and improved metabolic function.
Health.com notes that “water fasting may allow cells to break down old, damaged parts through autophagy,” potentially reducing risk factors for several diseases.
However, medical professionals advise against unsupervised fasting beyond the 24 and 72 hour period, as extended fasts can lead to serious health risks such as dehydration, hypoglycemia, and worsening of pre-existing health conditions like diabetes, cardiovascular disease and kidney disease.
Newsweek spoke with Nelly J. Aguilar, a writer and creator who recently undertook a 30-day water-only fast. “I’m no stranger to fasting,” Aguilar explained. “I’ve experimented with several shorter fasts, and intermittent fasting is how I usually space my meals. But a 30-day water-only fast was unfamiliar territory—something I felt compelled to dive into, for better or worse.”
Nelly J. Aguilar pictured before (L) and after (R) losing 25 pounds on her 30-day water fast.
Nelly J. Aguilar pictured before (L) and after (R) losing 25 pounds on her 30-day water fast.
Nelly J. Aguilar
“Fasts are remarkable, but integrating them as a practice of faith is even better,” Aguilar said.
“The closeness you feel with your creator, with the foundational truths that make up your existence, is different when you set aside food to worship, pray, and study. While there were times when I was violently famished, I reminded myself to be in the present. I kept telling myself this was a season and it would eventually come to a close.”
Reflecting on the physical impact of her journey, Aguilar noted she lost 25 pounds, which left her feeling physically lighter and more connected to her body. “I could move and bend more easily, and I had more reign over my body without all those unnecessary pounds holding me down,” she shared.
“My complexion turned brighter and I felt healthier. The dark circles under my eyes went away and I saw a glow in my eyes because of how good my body was feeling. Looking in the mirror was animating; I could see a lean body emerge from what was once lazy weight gain. It felt fruitful to do something nourishing and revitalizing for my body.”
While some people fast for spiritual or religious purposes, with participants often describing a heightened sense of well-being and clarity, experts warn that prolonged water-only fasts can be dangerous without supervision.
Marcelle Rose Bant, a registered nutritionist and eating disorder specialist, told Newsweek, “Extended water-only fasting beyond 48 hours can pose serious physical and psychological risks. Prolonged fasting deprives the body of essential nutrients, which can lead to muscle breakdown, electrolyte imbalances, and impaired cognitive function.”
She adds, “For those with a history of disordered eating or an unhealthy relationship with food, such extreme restrictions may trigger the reemergence of disordered behaviors, obsessive thoughts about food, and even binge eating once the fast ends. This rise in long fasts likely reflects societal pressures for quick fixes and unrealistic body ideals.”
Ana Casas, M.D., a longevity medicine expert, told Newsweek, “A recent narrative review of clinical trials on prolonged water fasting published in Nutrition Reviews identified some short-term metabolic benefits, but these did not last beyond the fasting period itself. In addition, weight loss during prolonged fasting was found to primarily impact lean muscle mass, accounting for two-thirds of the total loss, with only one-third being fat.”
Dr. Casas highlighted that intermittent fasting could be a healthier approach. “With intermittent fasting, eating is limited to an 8-hour window while fasting occurs for the remaining 16 hours, during which non-caloric beverages like water can help prevent dehydration. This is a healthier way of fasting for weight loss and additional health benefits.”
Anyone considering a fast longer than 72 hours should consult a healthcare provider and conduct the fast under medical supervision.
Update 10/29/2024 10:53 a.m. ET: This article was updated with expert comment to reflect safety concerns regarding prolonged water fasting.