While there is still some debate about the effect of physical activity on our appetite, several studies have shown that exercise alters appetite-related hormones, leading to a suppression in hunger and caloric intake.[1],[3] Other studies have linked side effects of exercise such as body temperature, dehydration, and digestive function to the reduction of food intake.[4] Now, for the first time, recent research has shown that exercise actually changes the way our brain responds to the very idea of food.
According to a small study published in the March Journal of Applied Physiology, "60 minutes of moderate exercise reduced neuronal responses in brain regions consistent with reduced pleasure of food, reduced incentive motivation to eat, and reduced anticipation and consumption of food."
Brain MRIs of 30 healthy subjects were performed immediately after both a 60 minute non-exercise rest state, and after 60 minutes of moderate exercise on a stationary bike. Visual food cues and questionnaires were used to determine the level of the subject's appetite. Results from the MRIs revealed a decreased neuronal response in food reward regions (insula, putamen, rolandic operculum, and orbitofrontal cortex) after aerobic exercise, as well as reduced activity in the right rolandic operculum, which is consistent with reduced incentive to eat, anticipation of food consumption, and reduced pleasure of food. These images were consistent with the subject's self-reported decrease in hunger, prospective food consumption, and significantly increased feelings of fullness after the exercise trial. In other words, exercise makes you think less about eating, and reduces the pleasures and feelings of reward we get from food.
While this data pertains to the effects of one isolated episode of exercise on the behavior of these brain regions, another recent study from the February issue of Physiology and Behavior of 12 overweight/obese but otherwise healthy adults observed that six months of chronic exercise training significantly reduced brain activity in the food reward region (insula) and other visual brain regions known to be important in food intake regulation.
These findings provide new insight into the extensive benefits of exercise for not only our physical health, but also our mental health and behavior. So the next time you're craving that candy bar, maybe take a moment to do a round of jumping jacks, or better yet, jog those cravings right out of your memory!
References:
[1.] Broom DR, Stensel DJ, Bishop NC, Burns SF, Miyashita M. "Exercise-induced
suppression of acylated ghrelin in humans." J Appl Physiol 102: 2165-2171, 2007
http://jap.physiology.org/content/102/6/2165.full
[2.] Cornier M-A, Melanson EL, Salzberg AK, Bechtell JL, Tregellas JR. "The effects of exercise on the neuronal response to food cues." Physiology & Behavior 105: 1028-1034, 2012.
http://www.sciencedirect.com/science/article/pii/S0031938411005531
[3.] King, James A., Lucy K. Wasse, and David J. Stensel. "The Acute Effects of Swimming on Appetite, Food Intake, and Plasma Acylated Ghrelin." Journal of Obesity 2011 (2011): 1-8
http://www.hindawi.com/journals/jobes/2011/351628/
[4.] Nero, Evero, Laura C. Hackett, Robert D. Clark, Suzanne Phelan, and Todd A. Hagobian. "Aerobic Exercise Reduces Neuronal Responses in Food Reward Brain Regions." Journal of Applied Physiology 112.5 (2012).
http://jap.physiology.org/content/early/2012/02/27/japplphysiol.01365.2011.full.pdf+html?sid=8a327ba6-d25a-42d6-90bb-0a6f2a1151b9
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