Medscape Medical News > Features
Marilynn Larkin
August 14, 2024
Dry fasting, the practice of going without food and water, has enthusiastic advocates on TikTok, X, YouTube, and other social media platforms. Devotees claim a wide range of health effects, but medical professionals advise caution to ensure that the practice does more good than harm, especially for individuals with diabetes.
Purported benefits and risks vary, depending on who is following the regimen and how long they abstain from food and water. Advocates on social media assert that dry fasting makes “intuition skyrocket” and puts autophagy on “overdrive.” Although such statements may rev up followers, there is little evidence to support these and many other dry-fasting claims. In fact, several physicians warned about unintended consequences.
“I had one patient who followed this fasting method often, and over time she developed kidney stones that led to a severe infection,” Deena Adimoolam, MD, an endocrinologist in private practice in New York City and New Jersey, told Medscape Medical News. “Lack of both water and food can fuel hunger and increase the likelihood of overeating or binge eating once the fast is completed, which does not lead to weight loss. Untreated dehydration can lead to loss of consciousness.”
“For individuals with type 2 diabetes, dehydration can exacerbate hyperglycemia and increase the risk of complications such as diabetic ketoacidosis (DKA),” Abeer Bader, lead clinical nutrition specialist at the Massachusetts General Hospital Weight Center in Boston, told Medscape Medical News. “Research also consistently shows that adequate hydration is crucial for maintaining physical and cognitive performance.”
Dry fasting also can lead to electrolyte imbalances, and the risk is higher for those with diabetes due to potential underlying kidney issues, Bader noted. “Prolonged dry fasting can result in nutrient deficiencies. For individuals with diabetes, maintaining adequate nutrition is crucial to manage blood sugar levels and overall health. The lack of both food and water can exacerbate deficiencies.”
Joanne Bruno, MD, an endocrinologist at NYU Langone Health, added, “Certain medications used for the management of type 2 diabetes, such as SGLT2 inhibitors, can cause dehydration. It is critical that patients stay well hydrated while on these medications to avoid serious side effects such as euglycemic DKA.”
What Exactly Is Dry Fasting?
Defining dry fasting, like any kind of fasting, has remained a challenge, according to authors of the first international consensus on fasting terminology, published on July 25 in Cell Metabolism. The clinical terminology “has remained heterogeneous and often confusing, with similar terms being used to define different fasting regimens…reflecting the manifold contexts in which fasting is practiced.”
Indeed, dry fasting was among the most discussed terms by the consensus panel and went through several rounds before the panelists came to agreement. A few experts were critical of the practice, whereas those familiar with religious fasting traditions, such as during Ramadan, were clear about the importance of including this term in the consensus process.
“The dissent was resolved by the clarification that this form of fasting has historical and geographical extensions and that the present consensus process did not aim at evaluating therapeutic effectiveness or safety for any term defined,” the authors wrote.
The panel concluded that dry fasting is not the same as total or complete fasting because the latter can include water (such as water-only fasting). Their final definition of dry fasting is ”a fasting regimen during which a voluntary abstinence from all foods and beverages, including water, is practiced for a certain period of time.”
Different types of fasting regimens, such as intermittent fasting, may include dry fasting, in which case it is referred to as “intermittent dry fasting.” This is defined in the consensus as intermittent fasting regimens that involve abstaining from food and fluid intake during the fasting interval, which typically lasts 9-20 hours.
Most dry fasts, including religious ones, are maintained for a specific interval and are followed by a refeeding period. These fasts are not starvation, defined as no food or water intake for days.
What the Evidence Says
All that said, dry fasting by any other name remains dry fasting. “Abundant” evidence from animal studies suggests the potential of various types of fasting for disease prevention and treatment in humans, noted the authors of the consensus report, Along with the risks described above, small studies have explored short-term effects in people, all of which have yet to be established by larger and longer-term studies.
In a recent small study, researchers at Baylor College of Medicine, Houston, Texas, reported that dawn-to-dusk dry fasting for 30 days reduced levels of inflammatory cytokines in the 13 participants with a high body mass index. Earlier work by the group showed that dawn-to-dusk dry fasting for 30 days induced “anti-atherosclerotic, anti-inflammatory, and anti-tumorigenic proteome” in peripheral blood mononuclear cells of 14 individuals with metabolic syndrome (The researchers declined to comment for this Medscape Medical News story.)
Importantly, the health effects can vary among individuals for unknown reasons, found a recent cross-sectional study of fasting blood glucose (FBG) changes in 181 patients with type 2 diabetes during Ramadan intermittent fasting (RIF), which involves dry fasting during daylight hours for 1 month. The researchers classified participants into three groups: reduced average FBG levels (44%), no change in FBG levels (24%), and increased FBG levels (32%). The authors wrote that further studies are needed to identify factors associated with the differences and to identify “those who are great candidates for RIF.”
In contrast to some of the concerns expressed by clinicians, an exploratory study of daytime dry fasting among 34 healthy Baha’i volunteers in Germany concluded that the 19-day regimen “is safe, has no negative effects on hydration, can improve fat metabolism and can cause transient phase shifts of circadian rhythms.” The authors acknowledge that a larger number and more diverse participants are needed to validate the findings and assess the impact on long-term health.
What to Advise Patients
For patients who want to fast as part of their weight loss regimen or to help manage diabetes, clinicians can consider suggesting “alternate ways of eating that might achieve similar goals,” Bader said. One is intermittent fasting without dry fasting: the 16:8 method (16 hours of fasting, 8 hours of eating) or the 5:2 method (normal eating for 5 days, reduced calorie intake for 2 days), which can support improved insulin sensitivity and metabolic health.
Caloric restriction can also work if the patient maintains a balanced diet that includes all essential nutrients, she said. A low-carbohydrate diet that focuses on limiting carbohydrate intake while increasing consumption of lean proteins and healthy fats has been shown to lower blood sugar levels and improve insulin sensitivity.
Other healthy strategies for patients include the Mediterranean diet, which emphasizes whole grains, fruits, vegetables, nuts, seeds, olive oil, and lean proteins such as fish, or a similar plant-based diet with less animal protein. Bader advises cultivating mindful eating, which involves paying attention to hunger and fullness cues, making thoughtful food choices, and focusing on being present during meals.
“Each of these dietary strategies offers potential benefits for managing type 2 diabetes and improving overall health,” Bader said. “I have not had any patients who have tried dry fasting specifically. However, I have encountered scenarios where individuals abstained from food and beverages due to religious practices. In those cases, we focused on ensuring that they maintained proper hydration and balanced nutrition during their eating periods to manage their diabetes effectively and prevent complications.”
Overall, Adimoolam suggests that clinicians help patients find a weight-loss plan that works best for them based on understanding the calories in the foods they like and don’t like. For fasting regimens, patients can be encouraged to choose one with fluids when possible, as well as intervals of time to fast and eat that work best for their lifestyle.
Bader, Bruno, and Adimoolam report no relevant conflicts.
Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, The Lancet (where she was a contributing editor), and Reuters Health.
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