Are Obese Kids Prone to Allergies?Tuesday, March 17, 2009
Several studies have suggested a link between the increasing rates of obesity and the increasing rates of allergies. However, much about this link remains doubtful.
The largest study on this issue was recently published by Cynthia Visness and colleagues from the University of Chapel Hill, North Carolina, USA in the Journal of Allergy and Clinical Immunology.
In this study, Visness and colleagues examined data from the 2005-2006 National Health and Nutrition Examination Survey (NHANES), which included data from over 4000 kids aged 2-19. Allergies were determined both by a symptom questionnaire on previous diagnoses of hay fever, eczema, and allergies as well as measurement of allergen-specific serum IgE levels.
Obese kids had significantly (~30%) higher total IgE levels and a ~60% higher rate of food sensitization compared to normal-weight kids. C-reactive protein levels were also higher in obese kids suggesting signs of systemic inflammation. It is however important to note that there was no relationship between obesity and reported allergy symptoms or hay fever
Nevertheless, the authors conclude that there may indeed be a higher risk for (food-related) allergies in obese kids.
Obviously, there are limitations to the interpretation of these findings. As this is a cross-sectional study, no inference can be made on what causes what – does obesity contribute to food allergies (obese kids have been shown to eat a greater variety of foods – see yesterdays post in this regard) – or do food allergies contribute to obesity? Or are both obesity and allergies related to some common phenomenon such as reduced breast feeding, and simply associated without being causally linked?
Obviously, as we do not know if the relationship is causal, it would be premature to suggest that preventing or treating obesity would reduce allergies or that treating allergies would reduce the risk for obesity – this can only be shown by appropriately designed intervention studies.