Washington: Obesity is known to be causing a host of other illness. Now, a new study has found that people carrying extra kilos experience more pain then those with normal weight.

The study of more than one million people, published in the journal Obesity, found the heaviest individuals also reported highest rates of pain -- about 254 per cent more than the normal-weight people in some cases.

"Our findings confirm and extend earlier studies about the link between obesity and pain," study author Arthur Stone of Stony Brook University was quoted as saying by LiveScience.

Previous studies have also showed a link between weight and various painful conditions, including including lower back pain, tension-type or migraine headache, fibromyalgia, abdominal pain and chronic widespread pain.

In the new study, Stone and his colleagues analysed data from telephone surveys conducted between 2008 and 2010 by the Gallup Organisation. Respondents indicated their height and weight, which researchers used to calculate body mass index (BMI), and also answered questions about pain, including whether they had "experienced pain much of the day yesterday."

The participants were classified as normal weight if they have their BMI below 25; overweight (25 to below 30); obese I (30 to below 35); obese II (35 to below 40); and obese III (40 and over). Results showed that, 36.8 per cent of participants were classified as low-to-normal weight, 38.3 per cent were overweight, and the rest were obese.

Compared with participants who ranked as low-to-normal weight, the overweight group was 20 per cent more likely to report pain yesterday, while the obesity-I group reported 68 per cent higher rates of pain, a number that climbed to 136 per cent and 254 per cent for obesity-II and obesity-III groups, respectively.

To tease out the cause of the pain, the researchers also asked participants about any chronic pain conditions.

"We expect people who have chronic pain conditions to be more likely to report pain yesterday than those without such conditions, and that is what we found," Stone said.

But those conditions didn't account for all the reasons for the pain-obesity link. The researchers statistically accounted for any musculoskeletal disease, which is often linked to obesity due to the extra strain on joints from the weight.

"What we found is that the weight-pain link persisted, suggesting that there are other factors driving the association," study co-author Joan Broderick said.

One idea is that an obese person's excess fat triggers physiological processes that result in inflammation, which is associated with pain, the researchers said.

Another explanation, they said, could be depression which has been shown to be associated with pain. Obesity, depression and chronic conditions have genetic influences, suggesting underlying genetics could be partially to blame, they added.

(Agencies)