They compared these mice to another group of mice eating relatively lean foods with just 11 percent calories from fat, reports Huffington Post. To the surprise of no one, the mice that scarfed down the high-fat diet increased their waist size by 11 percent at the end of the six-week study.
After the mice raised on a high-fat diet were switched to a healthier one, they acted more anxious and depressed. The researchers then examined the brains of the mice and discovered significant changes had occurred: Mice on the high-fat diet had increased levels of corticosterone — a hormone associated with stress — and CREB, a protein closely linked to dopamine functioning.
The new study offers the first evidence that these withdrawal-like symptoms can occur when people cut down on highly processed foods, said lead study author Erica Schulte, a doctoral candidate in psychology at the University of Michigan. Based on the participants' self-reported symptoms, withdrawal symptoms were most intense between the second and fifth days after attempting to reduce junk-food consumption, which parallels the time span people live through during drug withdrawal, Schulte told Live Science.
The idea that food may be addictive after "heavy" use by some individuals is a controversial subject, Schulte said. Although prior research studies in animals and humans have shown some biological and behavioral similarities between substance-use disorders and addictive-like consumption of highly processed foods, no studies have looked at whether reducing junk food can trigger withdrawal symptoms in people, she noted. In the study, the researchers developed a new tool modeled after the withdrawal scales that are used to assess symptoms that occur after people quit smoking or stop using marijuana.
This modified questionnaire was given to more than adults who had dieted during the past year by attempting to cut down on junk food. The new study is believed to be the first of its kind to evaluate withdrawal symptoms that people go through when they stop eating highly processed foods, such as pastries, French fries, and pizza.
Researchers agree that the addictive qualities of tobacco, drugs, or alcohol affect the brain similarly and cutting back can lead to negative side effects that can make it difficult to reduce intake. Anxiety, headaches, irritability, and depression are some of the outcomes.
Understanding whether withdrawal may also occur with highly processed foods was an essential next step in evaluating whether these foods might be capable of triggering similar addictive processes, researchers say.
Schulte and colleagues created the first self-report tool to measure the physical and psychological withdrawal symptoms among people, then asked adults to report what happened when they reduced the amount of highly processed foods they ate in the past year.
The participants reported that sadness, irritability, tiredness, and cravings peaked during the initial two to five days after they quit eating junk food, then the negative side effects tapered off, which parallels the time course of drug withdrawal symptoms, according to the study.
Schulte says future studies will analyze the behavior in real time rather than the retrospective approach in the current findings. The study suggests that withdrawal symptoms may make dietary changes challenging, which may contribute to people reverting back to bad eating habits, says coauthor Ashley Gearhardt, associate professor of psychology.
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