Dr. Michael Omidi discusses a clinical study that found that the brains of overweight women react differently to exercise than the brains of fit women.

A new study published in The International Journal of Obesity suggests that women’s brains react differently to images of exercise depending upon if they are fit or overweight.[1]

The study, conducted by medical scientist affiliated with the Key Laboratory of Cognition and Personality at Southwest University in Chongqing, China, studied 26 women – half of which were fit, while the other half were overweight or obese – and measured their brain activity when shown pictures of women either sedentary or enjoying vigorous exercise.

Before the images were shown, the subjects filled out a questionnaire, which included questions relating to if they were likely to feel embarrassed by exercising in public, if they felt being healthy and active would make them more popular and if they were likely to feel physical discomfort after or during exercise. The answers to these and other questions were to help the scientists gauge the extent to which the subjects found exercise pleasant or unpleasant.

Next, the subjects were placed inside an MRI (magnetic resonance imaging) machine, which measures brain activity via the amount of blood flow to different areas. The subjects were then shown 90 photographs of women happily engaged in different physical activities – dancing, running and playing sports. The subjects were then asked to actively imagine themselves engaged in these activities, and even use gestures as much as they could while in the MRI machine.

Next, the women were shown pictures of women sitting, reclining and lying down. Again, the subjects were asked to imagine themselves doing the same.

The two categories of women demonstrated the opposite results. While the overweight/obese women had more activity in the regions of the brain that indicate feelings of displeasure during the exercise photographs, the fit women’s brains were more active in the areas that process feelings of being rewarded. Conversely, the overweight/obese women felt rewarded during the sedentary images.

A previous study centered on fit and overweight women’s reactions to images of eating and food yielded similar results. When overweight women were shown pictures of food being prepared, the putamen, or reward section of the brain, showed increased activity.

When fit women were shown pictures of food, the portion of the brain that registers satiety was active. In other words, the overweight/obese women felt happy and comforted when shown pictures of food, but thin women felt full.

It would be interesting to know how many of our natural reactions to exercise and food are determined by our sense of ourselves as thin or overweight people. Did the reactions trigger the weight gain, or did the weight gain trigger the reactions? Ideally, there will be follow-up studies, which will hopefully answer lingering questions.

Would the results change if the overweight women lost weight or began exercising? Were the fit women used for the study always fit? Does your personal response to exercise and food predict whether or not you are at risk for becoming overweight?

It is interesting to note that although many of the overweight women stated that they believed that they would be embarrassed by public exercise, they also believed that exercise and being healthy would make them more popular.

By Michael Omidi

[1] Reynolds, Gretchen: How Being Heavy or Lean Shapes Our View of Exercise New York Times 1/8/2014

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