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Obesity linked to asthma

Obese people face a greater risk of developing asthma, a study has revealed.

In a study of some 4,500 men and women from the National Health and Nutrition Examination Survey for 2005-2006, researchers in the US found the risk of developing the allergy was more than tripled for the most obese individuals compared to people considered to be "normal" weight.

After splitting the group into three separate weight categories - normal, overweight and obese - the team from the Palo Alto Medical Research Institute in California, writing in the journal Allergy, found that 12% of those in the obese category suffered from asthma compared to 6% in the normal weight group.

The likelihood of developing asthma also rose in line with an individual's body mass index (BMI), the researchers said.

Despite the apparent link between the two factors, the researchers said they could still only speculate on why obese people are more likely to have asthma.

One possible cause is the system-wide, low-grade inflammation witnessed in obese people, while others have suggested that a resistance to insulin could also lead to the development of the allergy.

Dr Jun Ma of the Palo Alto Medical Research Institute said that although no evidence had yet been found linking insulin-resistance to asthma, it remained a potential cause.

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