Despite a widely held belief that the potential benefits of exercise on weight management are related to ‘burning’ calories, I recently proposed that the real effect of exercise is in helping regulate food intake.
This is because exercise directly affects many of the psychological and emotional factors that can drive overeating and promote weight gain.
A study by Goldfield and colleagues from the Children’s Hospital of Esatern Ontario in Ottawa, just published in the Journal of Physical Activity and Health, now examined the relationship between physical activity and psychological adjustments in adolescents.
The study included a total of 746 girls and 513 boys, who responded to surveys on leisure time physical activity, depressive symptoms, anxiety, and body image.
The researchers found a ‘dose-response’ relationship between the reported intensity of regular physical activity and psychological distress, in that those who performed greater bouts of vigorous exercise exhibited better psychological adjustment than adolescents engaging in mild to moderate intensity activity.
Interestingly, there were gender differences in this relationship: while vigorous physical activity was associated with less depression but not less anxiety in boys, girls with higher activity levels reported less anxiety but not less depression.
As readers may already guess, the main problem with interpreting the finding of this cross-sectional study is that it shows a relationship but cannot prove or even imply causality (a common mistake in the reporting of this type of study).
Thus, it could well be that boys with less depression and girls who are less anxious are the ones who participate more in vigorous physical activity and that treating depression and anxiety in boys and girls, respectively, would lead to increased physical activity.
It would, certainly take an intervention study before we can conclude that psychological function can indeed be improved by exercise.
Nevertheless, there are other intervention data that do suggest that regular physical activity can improve mental health including self-esteem and it is very likely that any such improvements may translate into better ingestive behaviours.
As suggested before, studies exploring the effect of physical activity on body weight should probably also carefully assess the impact of such activity on psychological factors and ingestive behaviours before equating any weight loss with the impact of exercise on ‘calories out’.
Goldfield GS, Henderson K, Buchholz A, Obeid N, Nguyen H, & Flament MF (2011). Physical activity and psychological adjustment in adolescents. Journal of physical activity & health, 8 (2), 157-63 PMID: 21415442