Eric Hopton for redOrbit.com – Your Universe Online
If you have ever succumbed to a craving for high-calorie snacks, and most of us surely have, you may not feel quite so bad after reading a study by the School of Public Health and Health Systems and the Department of Kinesiology at Canada’s University of Waterloo. What you may have thought was a personal weakness could have been a simple evolutionary neurological response.
The researchers discovered that such over-indulgence may be due to lapses in a small and very specific area of your brain known as the dorsolateral prefrontal cortex, or DLPFC. The DLPFC is known to play a big part in the brain’s “executive functions,” helping the individual exercise control or restraint over otherwise automatic or “knee-jerk” reactions.
The report, which was published in the September edition of the Psychosomatic Medicine section of the Journal of Biobehavioral Medicine, describes the results of the study in detail. The aim of the research was to establish if there was any causal relationship between DLPFC function and “dietary self-control” as manifested by both visceral cravings and actual consumption.
The study used a sample of 21 young women aged between 19 and 26 years old, all students on undergraduate psychology courses who had admitted “strong and frequent cravings” for high-calorie foods like chocolate and potato chips. The students were either paid $40 or were given the chance to win a 16GB iPad in a drawing and, of course, got to try lots of their favorite foods in the interest of science.
The subjects were shown pictures of high-calorie foods in order to stimulate cravings. Then magnetic stimulation was applied to the DLPFC area of the brain using “continuous theta-burst stimulation” to suppress DLPFC activity. After the magnetic stimulation, the women exhibited increased cravings, in particular for the more appetizing choices like milk chocolate and potato chips. In subsequent taste tests they ate more of the appetizing foods than other foods like dark chocolate and soda crackers which were deemed to be less “appetitive.”
In effect, what these tests demonstrated was that suppressing DLPFC activity not only inhibits self-control but also increases “reward sensitivity.” In other words, the brain is subject to a double assault as high-calorie foods become more attractive and the pleasure response is heightened.
In what the study authors refer to as “the modern obesogenic environment,” this work may have important implications in understanding the neurological basis for “dietary self-restraint.” Human preference for calorie-dense foods is deep seated and, say the Waterloo scientists, “potentially driven by evolutionary pressures to optimize investment return per unit of energy spent foraging.” This preference would have been an evolutionary advantage when our species had unreliable food resources and needed to maximize opportunities when they arose. But in the modern developed world high-calorie choices are abundant and pushed at us relentlessly in what the authors call “ubiquitous environmental cuing of such foods through media advertising.” These changes have helped to bring about a rapid and serious increase in global levels of obesity and other chronic food-related illnesses.
“Interventions aimed at enhancing or preserving dorsolateral cortex function in healthy populations may reduce the likelihood of obesity and other chronic conditions” says Peter Hall, a senior author of the study. According to Hall, regular aerobic exercise, controlling alcohol intake, and getting plenty of sleep can all keep the brain in good shape and help us fight the demons of temptation.
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