Temple University researchers in Philadelphia found that obese women reported their activity levels most accurately, when compared to overweight and normal weight women.

Lead author Tracy Oliver compared the amount of activity reported by the women to the actual amount of activity as measured by an accelerometer -- a device that measures movement and acceleration in the course of a year.

At the first measurement, and a second three months later, obese women most accurately reported the amount of physical activity they were getting. After 12 months, all three groups were reporting on their activity levels more accurately.

"The ability to estimate the amount of minutes engaged in physical activity is a difficult task for many, however the accuracy of this estimate can increase with education and participation in physical activity over time," Oliver said in a statement.

The study is scheduled to be presented at The Obesity Society's annual meeting in Phoenix.