Research is turning on its head the idea that lazy people naturally gain weight. Instead, a new study from UCLA says junk food can stifle motivation. That means it's likely that weight gain makes people lazy.
"Now you can blame laziness on your diet, instead of your personality," says an article in USA Today. "Researchers at UCLA have conducted experiments that suggest laziness does not beget weight gain; weight gain begets laziness. More specifically, and a bit surprisingly, junk food begets laziness."
The research is published in the journal Physiology and Behavior.
For the study, life scientists devised two different diets and then placed 16 rats on each one for six months, according to background information on the study, which was funded in part by the National Science Foundation. While both diets were similar in fat, protein and total carbohydrates, the junk food diet had simple carbohydrates, while the healthful diet used complex carbohydrates.
Over three months, the rats gained weight very differently based on their diets; the rats who ate junk food "became noticeably fatter," said the researchers, who were led by Aaron Blaisdell, professor of psychology and a member of UCLA's Brain Research Institute.
They found that junk food may lead to fatigue, which leads to laziness and to weight gain.
According to an article on the study in the Los Angeles Times, "Anecdotally, Blaisdell said the two groups of rats seemed to have the same energy level — so it's not that the obese rats had grown more lethargic overall than the thin rats. Instead, he thinks it is possible that the refined diet is changing the chemistry inside these rats' brains."
"Overweight people often get stigmatized as lazy and lacking discipline," Blaisdell said. "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."
He also noted that rats and humans have similar physiological systems, so the findings are likely to hold true for humans, as well.
Researchers switched the rats' diets six months later to see what would happen. For nine days, the heavier rats ate more nutritiously, but it neither reduced their weight or improved their reaction time on assigned tasks. The leaner rates who ate junk food for nine days didn't gain noticeable weight or lose ground on their assigned tasks.
"These findings suggest a pattern of consuming junk food, not just the occasional binge, is responsible for obesity and cognitive impairments," Blaisdell said in the background information.
"There's no quick fix," he added.
The news release from UCLA said that "Blaisdell, 45, changed his own diet more than five years ago to eat 'what our human ancestors ate.' He avoids processed food, bread, pasta, grains and food with added sugar. He eats meats, seafood, eggs, vegetables and fruits, and he has seen dramatic improvements in his health, both physically and mentally."
"I've noticed a big improvement in my cognition," he said. "I'm full of energy throughout the day, and my thoughts are clear and focused."
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