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LOS ANGELES — A diet full of processed food isn't only a potential cause of obesity, it can also lead to fatigue and laziness, according to new research.
In a study, rats were split into two groups and either given a normal diet of mostly unprocessed foods, like fish and corn, or a highly processed diet with lower quality ingredients, according to researchers from the University of California Los Angeles. They said the rats on the simulated junk food diet gained a significant amount of weight and became more tired and sedentary.
The findings apply to humans because their physiological systems are similar to rats, according to lead researcher Aaron Blaisdell.
"Overweight people often get stigmatized as lazy and lacking discipline," lead researcher Aaron Blaisdell said in a statement. "We interpret our results as suggesting that the idea commonly portrayed in the media that people become fat because they are lazy is wrong. Our data suggest that diet-induced obesity is a cause, rather than an effect, of laziness. Either the highly processed diet causes fatigue or the diet causes obesity, which causes fatigue."
Researchers measured the rats' activity levels by giving the rats tasks like pressing a lever to receive rewards of food or water. The overweight rats did not perform as well, according to the study.
"The rats on the junk food diet demonstrated impaired performance, taking substantially longer breaks than the lean rats before returning to the task," a release from UCLA reads. "In a 30-minute session, the overweight rats took breaks that were nearly twice as long as the lean ones."
Blaisdell said the study also suggests obesity and cognitive impairments are caused by a pattern of consuming junk food and not just the occasional binge. After six months, researchers switched the rat's diets for a period of nine days, but didn't see any significant change in weight or activity during that time.
There doesn't seem to be a quick fix to the problem, he said.
Researchers said other side effects of the junk food included the growth of numerous large tumors throughout the rats' bodies and an increased appetite.
On a personal note, Blaisdell said he cut processed foods out of his diet five years ago and has noticed a big improvement in his health and cognition.
"We are living in an environment with sedentary lifestyles, poor-quality diet and highly processed foods that is very different from the one we are adapted to through human evolution," he said. "It is that difference that leads to many of the chronic diseases that we see today, such as obesity and diabetes."
The research was published in the April 10 edition of the journal "Physiology and Behavior."
