DEVELOPMENT OF A WEIGHT LOSS INDEX FOR MEASURING WEIGHT LOSS SUCCESS IN OBESITY TREATMENT

Abstract

The Weight Loss Index (WLI) is a new method for evaluating weight loss over a period of time and can subsequently be used as a means to compare individuals in terms of their weight loss success. The formula for calculating the WLI is: {σ(tn+1 - tn)· [((Bn - 25) + (Bn - 25)) 0.5]}/T2 (Where n = observation number; t = number of weeks, months, or years; B = BMI value; and T = total time period of the observation (i.e. weeks, months, years)). This WLI eliminates classifying weight loss successes and failures at specific points in time, but rather provides a reference continuum that accounts for weight fluctuations, commonly seen in weight loss attempts. PURPOSE: The purpose of this study was to determine if the WLI is a more sensitive tool for evaluating changes in patient's body weight than evaluations performed by professionals. METHODS: Based on an anticipated response rate of 30%, and a sample size of 108, a total of 316 questionnaires were sent to clinicians and researchers dealing with the treatment of obesity in the United States. The questionnaire consisted of 10 case studies, with 4 weight loss scenarios per case study. The professionals were instructed to rank each scenario in terms of weight loss success, with 1 designating the most “successful” weight loss attempt, and 4 the least successful. Professional rankings were compared to the WLI rankings and analyzed using the Spearman's correlation coefficient. A coefficient of 0.75 with a two-sided confidence interval of ± 0.10 was determined as an indicator of adequate correlation between the WLI and the ability of professionals to choose the most “successful” weight loss attempt. RESULTS: A total of 127 questionnaires out of the 316 were returned for a response rate of 34%. A single Spearman's correlation coefficient of 0.5867 was derived by compiling all professional responses for every case study. CONCLUSION: Professionals were not able to rank weight loss successes among overweight patients as well at the WLI. The WLI therefore, is a good tool that allows objective comparison of individuals in terms of their weight loss attempts, even if there are small weight changes or fluctuations in body weight. The WLI also provides an objective numerical index with which professionals can compare different weight loss attempts against the standard BMI reference point of 25. Supported by the George Washington University Obesity Management Program