Being sedentary increases the risk of being overweight; however, a new UCLA study has found that eating junk food makes you lethargic and fat. The study is currently available online and is scheduled for publication in the April 10 print edition of the journal Physiology and Behavior.
A research team led by Aaron Blaisdell PhD, placed 32 female rats on one of two diets for six months. One group received a standard rat diet, consisting of relatively unprocessed foods such as ground corn and fish meal. The food fed to the other group was highly processed, lower quality, and had a high sugar content: a junk food diet. After three months, a significant difference was found in the amount of weight the rats had gained; the 16 rats on the junk food diet were noticeably fatter. Dr. Blaisdell noted, “One diet led to obesity, the other didn’t.” He added that the study also suggested that fatigue may result from a junk food diet. The study included giving the rats a task in which they were required to press a lever to receive a food or water reward. The rats on the junk food diet exhibited impaired performance; they took significantly longer breaks than the lean rats before returning to the task. In a 30 minute session, the overweight rats took breaks that were nearly twice as long as the lean ones.
In the second phase of the study, the rats’ diets were switched, and the overweight rats were given the more nutritious diet for nine days. However, this change, however, did not result in weight loss or improved lever responses. Furthermore, placing the lean rats on the junk food diet for nine days did not noticeably increase their weight or result in any reduction in their motivation on the lever task. Dr. Blaisdell noted that these findings suggest that a pattern of consuming junk food, not just the occasional binge, is responsible for obesity and cognitive impairments. He said, “There’s no quick fix.”
Blaisdell is of the opinion that the study’s findings are extremely likely to apply to humans, whose physiological systems are similar to rats. He noted, “Junk food diets make humans—and rats—hungrier. He explained, “Overweight people often get stigmatized as lazy and lacking discipline. 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.”
A disturbing finding of the study was that the rats on the junk food diet grew large numbers of tumors throughout their bodies by the end of the study. The rats on the healthy diet had fewer and smaller tumors that were not as widespread.
Dr. Blaisdell is 45 years old. More than five years ago he changed his diet to consume “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. He noted, “I’ve noticed a big improvement in my cognition. I’m full of energy throughout the day, and my thoughts are clear and focused.”
Dr. Blaisdell’s research is focused on the relationship between health and lifestyle (diet and exercise) and the relationship between a junk food diet and cognitive impairments it may induce. He noted, “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. It is that difference that leads to many of the chronic diseases that we see today, such as obesity and diabetes.”