Does Junk Food Make You Lazy?
Obesity and overweight are famously big problems in modern America. But despite the fact that being super-sized is no longer a novelty, there’s still a stigma attached to being grossly overweight. The notion that obese people are lazy is widespread. And there’s some evidence that extra-large people are, in fact, less active. In many studies, overweight and obese people have reported feeling fatigued and having little energy. And that, of course, means they’re less likely to spend time exercising. Or even moving around.
But does being fat make you lazy? Or does being lazy make you fat? Or, to put it in less potentially offensive terms: Do less active people become overweight, or does being overweight make you less active? Research suggests that the latter is more likely. Earlier this year, psychology experts at the University of California Los Angeles reported on experiments conducted on mice. The mice were divided into two groups. One group was fed a poor-quality diet featuring lots of sugar and processed foods. The other got a diet featuring relatively unprocessed foods, such as ground corn and fishmeal.
Not surprisingly, mice in the “junk food” group became obese, while the other mice remained lean. But what was surprising was the change in the animals’ activity levels. Obese mice became markedly less active, even though activity led to a reward. They took longer breaks and appeared to be less inclined to expend effort. The investigators came to several interesting conclusions: 1) a junk food diet leads directly to obesity. 2) fatigue (which may lead to behavior that is interpreted as “laziness”) is a result of obesity, not the other way around. 3) the junk-food-diet animals grew numerous tumors. Which suggests that such a diet encourages cancer.
In a story about the research by Stuart Wolpert (UCLA Newsroom) lead researcher, Aaron Blaisdell, said the research showed “…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.” His recommendation for humans? Avoid processed foods and added sugar and get back to a more ancestral diet featuring fruits, vegetables, whole grains, seafood, meat and eggs. And say “no thanks” to junk food. You’ll stay lean and have more energy.
Aaron P. Blaisdell, Yan Lam Matthew Lau, Ekatherina Telminova, Hwee Cheei Lim, Boyang Fan, Cynthia D. Fast, Dennis Garlick, David C. Pendergrass. Food quality and motivation: A refined low-fat diet induces obesity and impairs performance on a progressive ratio schedule of instrumental lever pressing in rats. Physiology & Behavior, 2014; 128: 220 DOI: 10.1016/j.physbeh.2014.02.025