Obese people could be more likely to be injured on the job, according to a new study published in the May issue of the American Journal of Epidemiology.

Having a body mass index (BMI) in the overweight or obese range increases the risk of traumatic workplace injury, said the study by researchers at the Johns Hopkins Bloomberg School of Public Health's Center for Injury Research and Policy.

BMI is a measure of body fat based on an adult's height and weight. It is used to screen for weight categories that may lead to health problems. According to the Centers for Disease Control and Prevention, a BMI below 18.5 is considered underweight, 18.5- 24.9 is normal; 25-29.9 is overweight and over 30 is obese.

The researchers used medical and injury surveillance data on hourly workers employed in eight plants of the same aluminum manufacturer to determine whether increased BMI was a risk factor for workplace injury. The plants were scattered across the United States. Employees are grouped into five categories: underweight, normal, overweight, obesity levels I and II and obesity level III.

Of the 7,690 workers included in the study, 29 percent were injured at least once between January 2, 2002, and December 31, 2004. Approximately 85 percent of the injured workers were classified as overweight or obese. More than 28 percent of injuries occurred among employees classified as overweight, 30 percent in the obese I and II category and almost 34 percent in the obese III category.

The severely obese group who had a BMI of greater than 40 also had the most injuries to the hand/wrist/finger (22 percent) when compared to the same injuries in the other weight categories.

The researchers say that more work will be needed to test the effectiveness for reducing weight among hourly (non-office) employees who face a number of barriers to participating in worksite physical activity programs, such as the need to remove protective clothing for midday exercise and a lack of time because of additional employment or home responsibilities.