Validity and usefulness of medical chart weights in the long-term evaluation of weight loss programs.

The high rate of delayed recidivism seen in behavioral weight loss studies makes follow-up over a number of years essential. Unfortunately, these data are both expensive and difficult to collect. This report examines the validity of body weights routinely recorded in medical charts and their usefulness in the long-term evaluation of weight control programs. Comparison of 123 pairs of chart weights and research clinic weights recorded within 30 days of each other showed a mean difference of .06 lb (.03 kg) and a standard deviation of 2.38 lb (1.08 kg). This measurement error is considerably less than that seen in self-reported weights of obese adults. The accuracy, economy and relative ease of collection make the use of medical chart weights well suited for long-term evaluations of weight loss studies and other research purposes.