Accuracy of self-reported exercise and the relationship with weight loss in overweight women

PURPOSE: The purpose of this study was to compare self-reported exercise to a more objective measurement of exercise (i.e., Tri-Trac Accelerometer) and to assess whether there is a difference in weight loss between individuals who under- and over-report their exercise. METHODS: Fifty overweight females (BMI = 34.0 +/- 4.2 kg.m-2) who were participating in a behavioral weight control program were included in this study. Subjects were randomly assigned to a long-bout or a short-bout exercise condition, with both groups instructed to exercise 30 min.day-1 on 5 d.wk-1 for a period of 20 wk. The long-bout group was to exercise in one continuous session (e.g., one 30-min session per day), whereas the short-bout group was to divide the exercise into multiple 10-min sessions (e.g., three 10-min sessions per day). Subjects recorded their exercise in a daily exercise log and wore a Tri-Trac accelerometer for a 1-wk period to validate self-reported exercise bouts. RESULTS: Results showed that approximately 45% of the women over-reported the amount of exercise that they performed, and this did not differ between the long-bout and short-bout groups. Women who over-reported their exercise had significantly poorer weight loss across the 20-wk program than women who under-reported their exercise (6.3 +/- 3.6 kg vs 9.4 +/- 5.2 kg). CONCLUSIONS: The results of this study suggest that overweight women who over-report their exercise will have poorer weight loss while enrolled in a behavioral weight loss program compared with others enrolled in the program, and the Tri-Trac Accelerometer may be useful in identifying individuals who inaccurately report the amount of their exercise. The ability to classify individuals as either over- or under-reporters of their exercise may be helpful to weight loss therapists and lead to more successful treatment for obesity.