Reducing obesity may be as simple as replacing sweetened drinks with water, but the process by which it happens is more complex than just a drop in calories. Researchers at the University of Colorado found fructose stimulates the release of vasopressin, a hormone linked to obesity, and drinking water can suppress vasopressin.
Vasopressin, which is also linked to diabetes, is responsible for helping the body maintain its water levels. Scientists wanted to know why vasopressin is typically elevated in people who are obese or have diabetes.
Miguel Lanaspa, PhD and Richard Johnson, MD found when they fed mice fructose (sugar water) it stimulated the brain to make vasopressin. The vasopressin then caused the mice to store the sugar water as fat which led to obesity and caused the mice to be dehydrated. By removing the sugar and just giving the mice water they were able to reduce the obesity.
"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," Lanaspa said. He believes this is the first time scientists have been able to see how vasopressin works with dietary sugars to cause obesity and diabetes.
"We found that it does this by working through a particular vasopressin receptor known as V1b," Lanaspa said. "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."
The researchers say by studying vasopressin they have a better understanding of how dehydration can stimulate the formation of fat and why high salt diets may cause obesity and diabetes.
"This explains why vasopressin is so high in desert mammals as they do not have easy access to water," Johnson said. "So vasopressin conserves water by storing it as fat."
The study showed how drinking water protected against metabolic syndrome, which is a collection of conditions such as high blood pressure, high blood sugar and elevated triglyceride levels that increase the risk of heart disease, diabetes 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."
His colleague summed up their study by saying, "Sugar drives metabolic syndrome in part by the activation of vasopressin,” Johnson said. “Vasopressin drives fat production likely as a mechanism for storing metabolic water. The potential roles of hydration and salt reduction in the treatment of obesity and metabolic syndrome should be considered."