Researchers Find Mental Tasks Cause People to Eat More

As a so-called knowledge worker, who spends more time on my computer then on my mattress, I found the following article by Lee Dye, published on ABC News, Online, September 10, 2008, fascinating and frightening. The majority of women hold “Think-Work” positions. If focus and concentration stimulates our appetites as indicated in the sited study, we are going to have to find a new strategy for “desk-bound” wellness.

Angelo Tremblay noticed something odd every time he worked up a grant application for his research program in a Quebec university. He had a craving for chocolate chip cookies.

Now, thanks to research in his lab at the Universite Laval, he has a better understanding of why. It turns out that performing mental tasks, like trying to solve problems while working at a computer, stimulates the appetite so much that people tend to eat significantly more calories than they burned while performing the “knowledge-based” tasks.

In a study published in the current issue of Psychosomatic Medicine, researchers found a physiological basis for the spike in appetite. Mental work “destabilizes” the levels of insulin and glucose, two critical components in the body’s regulatory and energy machinery, thus stimulating the appetite, said Jean-Philippe Chaput, lead author of the study.

“The brain uses only glucose for energy,” unlike the “muscles, which use fat and glucose,” Chaput said in a telephone interview. So when the level of glucose, or sugar, becomes unstable, the brain demands more.

According to the research, participants consumed far more calories after performing mental tasks than they consumed after relaxing for the same period of time.

The study is quite small, involving only 14 women, so the results are only tentative, but Chaput said he and his fellow researchers have already embarked on a larger study involving 50 men and 50 women. Only women were used in the pilot study because it has been well established that men and women react differently to stress, and the researchers did not want to cloud the results.

At this point, however, the study indicates that a rapidly changing lifestyle toward “knowledge-based work,” like time spent at the computer or trying to solve mental challenges, may be a significant factor in the current obesity epidemic, Chaput said.

“There are a lot of people doing this kind of work now, compared to physical work in the past, so we postulate that it can explain in part” why so many people in so many countries are getting fat, he said.

As the researchers put it in their paper, “knowledge-based work represents the main working modality in a context of modernity.” In other words, many are spending fewer calories, but taking more in, because of changes in the work environment.

That’s true not only in the world of employment, but in the world of entertainment as well. Many people are spending more time playing computer games, some of which can be intellectually challenging, than playing tennis, for example.

The researchers are members of the university’s department of medicine, and they specialize in kinesiology, the mechanics and anatomy of human movement. The 14 women in the study were all students, ranging in age from 20 to 30 years. All were in good health, with no eating disorders, normal weight, and free of food allergies.

During a two-month period they were each required to participate in three 45-minute exercises consisting of relaxing in a chair, reading a document and writing a summary of 350 words, and “a cognitive task consisting of a comprehensive battery of computerized tests.”

Each participant was tested separately from the others.

Each “came into the lab at 8 a.m., and we gave each participant a standardized breakfast,” Chaput said. “After that we started the exercise at 10:30 a.m., one participant at a time, and they came every two weeks. At about 11:30 a.m. we gave them a buffet type of meal, comprising a lot of food.”

The food in the buffet was weighed and analyzed before and after the lunch, so researchers knew precisely how much and which type of food each participant had eaten. Various tests during each exercise also told the researchers precisely how many calories the participants were burning at the time.

The participants burned only about three calories more during each of the two “knowledge-based” experiments than during the 45 minutes when they rested in a comfortable chair. So the caloric expenditures were relatively quite low for mental tasks compared to the period spent relaxing.

But the intake was significantly higher. Participants consumed 203 more calories after the reading experiment, and 253 more calories after the computer tests, than the resting participants. That’s an increase of 23.6 percent and 29.4 percent, respectively.

Measurements of glucose and insulin became quite erratic during the mental tests. Glucose soared almost immediately when the participants were reading and then dropped dramatically. It dropped and remained below normal during the computerized tests. Insulin rose slightly during the reading test, and then dropped, and it dropped steadily during the computer tests.

That erratic performance by both glucose and insulin caused the appetite to rise, apparently in response to a need to restore the energy balance, the researchers conclude. The results probably would have been different if men had been included in the study, as they will be in future research. That’s because mental challenges provoke stress, and it “is expected to be higher in females than in males,” according to Chaput. That is also reflected in many other studies. He said women also tend to eat more following stress than men do, although “we don’t know why yet.”

Although the first study was limited to college-aged participants, Chaput said other research in his lab suggests that the same findings will apply to children as well as to older adults.

But if mental challenges cause people to eat more food, why aren’t nearly all college professors fat?

Simple, Chaput said. Eating is only part of the weight control “package,” he added. It’s possible to spend a lot of time working out problems at the computer if that is balanced with a reasonable amount of time working out, literally.

Some college professors, of course, are fat. Maybe the skinny ones use their computers on the treadmill.

Lee Dye is a former science writer for the Los Angeles Times. He now lives in Juneau, Alaska.

©2012 An Inconvenient Woman. All Rights Reserved.

American medical researcher Catherine Berkey and colleagues from Harvard Medical School (Boston, Massachusetts, U.S.A.), the Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital (Boston, Massachusetts, U.S.A.); and the Alvin J. Siteman Cancer Center, Washington University School of Medicine (St. Louis, Missouri, U.S.A.) led the research study based on the “Growing Up Today Study” (GUTS).

Their article “Weight Gain in Older Adolescent Females: The Internet, Sleep, Coffee, and Alcohol” appears online in The Journal of Pediatrics. Its authors are Catherine S. Berkey, Helaine R.H. Rockett, and Graham A. Colditz.

The objective of the study was to determine whether adolescent girls gained additional weight from the excessive use of the Internet, from insufficient sleep, and from the regular consumption of coffee and alcoholic beverages.

The researchers tested 5,036 girls from all fifty states of the United States between the ages of 14 and 21 years. The GUTS surveys were completed and returned to the researchers in 2001.

The surveys given to the young female subjects included typical activities during the past year on four exposures: (1) the recreational use of the Internet time, (2) amount of sleep, (3) consumption of caffeinated coffee, and (4) consumption of alcohol.

The researchers analyzed height and weight changes of the girls during a one-year period from 2000 to 2001, including body mass index (BMI), a measure of weight in relation to height. They adjusted the statistics with respect to adolescent growth and development, activity and inactivity, and other related factors.

What did the researches find from the results of their study?

The researchers found that the weight of the girls, on average went up faster with increased recreational use of the Internet, with decreased amounts of sleep, and with increased amounts of alcohol.

However, they also found that the weight of the girls was not affected—did not increase or decrease—when they drank coffee containing caffeine. In other words, coffee was found not to be a factor in weight gain or loss.

Specifically, they found that female subjects 18 years or old who slept five hours or less (on average) per night and who consumed two or more servings of alcohol per week gained more weight (in terms of BMI) than 18-year-or-older female subjects who slept eight hours per night and consumed less than two servings of alcohol per week.

In fact, the researchers found that the 18-year-old-or-older females gained, on average, four pounds (1.8 kilograms) over the one year-period when they did not get an adequate amount of sleep and when they drank more alcohol.

According to the abstract to their paper, the researchers concluded, “Older girls may benefit from replacing recreational Internet time with sleep and by avoiding alcohol.”

They also commented that, for example, a 19-year-old woman of average weight and height would gain 4 pounds (1.8 kilograms) if she were in the high-risk groups for Internet use, sleep, and alcohol consumption.

They suggested that spending recreational hours on the internet contributes to weight gain by reducing time spent doing physical activity.

Other comments from the researchers included the likelihood that sleep deprivation may make women (and men) less active during the day because of feelings of tiredness. In addition, insufficient sleep may also affect hormones and metabolism so that weight is more likely to be increased.

©2012 An Inconvenient Woman. All Rights Reserved.