New York- Obesity is known to be associated with metabolic diseases including diabetes, hypertension and cardiovascular diseases. Researchers have found that excess weight may also cause mental fatigue.The research has been published in the April issue of The FASEB Journal.
Earlier studies have shown that obesity can increase the risk of high blood sugar and other metabolic disorders if untreated. But compromised cognitive function, however, has not been associated as strongly with obesity as physical limitations.
"Although we were not fully surprised by this finding, this is the first study, to our knowledge, to be reporting mental exhaustion in high-fat diet-induced obese rats," said study principal investigator Chaya Gopalan from Southern Illinois University-- Edwardsville in the US.
In the instant study the researchers aimed to learn more about the onset of obesity and its impact on both physical and mental abilities by studying two groups of rats.
One group was fed a high-fat diet, and the other ate a standard diet for six weeks.
The research team measured the rats' weight, blood glucose and ketone levels twice a week. Ketones are chemicals made by the liver when there is not enough insulin in the body to convert glucose into energy.
In the fifth week, the researchers administered an open-field test, which measures speed and distance as the animals move through a maze in a given time frame and determine physical exhaustion.
A novel object recognition test, which measures mental exhaustion by analyzing the time the rats spend examining new and familiar objects, was given in the final week of the trial.
Both rat groups gained weight during the trial, but the high-fat diet group, not surprisingly, gained more than the control group.
The high-fat diet group performed poorly on the novel recognition test when compared with the control group. "Although we were not fully surprised by this finding, this is the first study, to our knowledge, to be reporting mental exhaustion in high-fat diet-induced obese rats," explained Chaya Gopalan, PhD, principal investigator of the study.
"One message from this study is to avoid [a] high-fat diet, which not only makes one become obese, but also has consequences on cognitive capability," the authors wrote.