UNIVERSITY PARK, Pa.,  Nov. 27 -- Obesity gradually numbs the taste sensation in rats to sweet foods and drives them to consume larger and ever-sweeter meals, U.S. researchers said.

"When you have a reduced sensitivity to palatable foods, you tend to consume it in higher amounts," Andras Hajnal of the Pennsylvania State University said in a statement. "It is a vicious circle."

Previous studies have suggested that obese persons are less sensitive to sweet taste and crave sweet foods more than lean people, Hajnal said.

Hajnal and colleague Peter Kovacs investigated differences by studying the taste responses of two strains -- OLETF and LETO rats.

The study, published in the Journal of Neurophysiology, found that compared to the lean and healthy LETO rats, the taste responses in OLETF rats mirror those in obese humans. These rats have normal body weight at first, but they tend to chronically overeat due to a missing satiety signal -- become obese and develop diabetes. The obese rats also show an increased preference for sweet foods and also are willing to work harder to obtain sweet solutions as a reward for their learning.

"When you have excess body weight, the brain is supposed to tell you not to eat more, or not choose high caloric meals," Hajnal said in a statement. "But this control apparently fails and thus the obesity epidemic is rising." (UPI)