Water is often recommended as a way to help people lose weight, but usually because it can help people feel full, reducing their appetite or food intake, or because it's a healthy, zero-calorie alternative to sugary drinks. Scientists may have now identified a physiological reason why drinking water can help reduce food consumption, and by extension, obesity. Reporting in JCI Insight, researchers found that the intake of sugar water intake stimulated the release of a hormone called vasopressin, and that water (without sugar) can reduce the levels of this hormone.
"The clinical significance of this work is that it may encourage studies to evaluate whether simple increases in water intake may effectively mitigate obesity and metabolic syndrome," said the senior study author Miguel A. Lanaspa, Ph.D., an associate professor at the University of Colorado School of Medicine.
Lanaspa and colleagues were interested in the connection between obesity and diabetes, and vasopressin, which helps control the levels of water in the body. In those metabolic disorders, vasopressin levels are abnormally high.
Using a mouse model, the researchers determined that when mice were given fructose water to drink, their brains produced more vasopressin. That increase in vasopressin caused the water in the mice to be stored as fat, leading to obesity and dehydration. When the mice were given regular water without added sugar, their obesity was alleviated.
Lanaspa suggested that this is the first time researchers have revealed how vasopressin can act on dietary sugar in this way and cause the development of obesity and diabetes.
"We found that it does this by working through a particular vasopressin receptor known as V1b," Lanaspa explained. "This receptor has been known for a while but no one has really understood its function. We found that mice lacking V1b were completely protected from the effects of sugar. We also show that the administration of water can suppress vasopressin and both prevent and treat obesity."
This study also suggests that dehydration can trigger fat formation.
"This explains why vasopressin is so high in desert mammals as they do not have easy access to water," said study co-author Richard Johnson, M.D. "So vasopressin conserves water by storing it as fat."
This research can explain why obese people have symptoms of dehydration, and how diets that are high in salt can lead to obesity and diabetes.
Water was a simple remedy, effectively protecting an animal model against a spectrum of conditions known as metabolic syndrome, which includes elevated measurements of blood pressure, blood sugar, and triglycerides that collectively increase the risk of type 2 diabetes, heart disease, and stroke.
"The best way to block vasopressin is to drink water," Lanaspa said. "This is hopeful because it means we may have a cheap, easy way of improving our lives and treating metabolic syndrome."
"Sugar drives metabolic syndrome in part by the activation of vasopressin. Vasopressin drives fat production likely as a mechanism for storing metabolic water," noted Johnson. "The potential roles of hydration and salt reduction in the treatment of obesity and metabolic syndrome should be considered."