Assessment of maximum weight change and duration of therapeutic effect for non-surgical treatment of obesity using an exponential model.

Efficacy of weight loss and maintenance therapies in obesity is difficult to quantify due to continuous weight changes over time. We assessed a single exponential model of weight changes during selected non-surgical therapies of non-diabetic obese subjects. We analyzed published mean weight data from 6 studies of ≥12 weeks duration, with comparable treatment groups, and ≥4 weight measurements during very low carbohydrate or fat diets, or treatment with Lorcaserin, Sibutramine or Orlistat. We fit data to a single exponential model to estimate maximum predicted weight loss or regain and duration of weight loss or regain for each therapy. A single exponential is the appropriate model as determined by Kolmogorov-Smirnov, constant variance, and Durbin-Watson tests. Validity of parameter estimates was indicated by coefficients of variation <25%. Sensitivity analysis showed that weight regain at the end of the weight loss phase affected parameter estimates in some instances, with variations of weight loss of 0.2-0.7% of basal. Estimated weight loss and regain were similar to observed weight changes in all studies. The model could also be used to assess dose-response relationships. Estimates from the model were used to compare concurrent obesity regimens using 95% confidence intervals, taking into account pre-determined minimal clinically important differences. This exponential model may provide accurate estimates of maximum achievable weight loss or regain and optimal duration of efficacy for a variety of non-surgical weight loss and maintenance regimens from published mean weight data and may be useful to more accurately evaluate weight loss and maintenance regimens.