28 research outputs found
Missing Data in Randomized Clinical Trials for Weight Loss: Scope of the Problem, State of the Field, and Performance of Statistical Methods
BACKGROUND: Dropouts and missing data are nearly-ubiquitous in obesity randomized controlled trails, threatening validity and generalizability of conclusions. Herein, we meta-analytically evaluate the extent of missing data, the frequency with which various analytic methods are employed to accommodate dropouts, and the performance of multiple statistical methods. METHODOLOGY/PRINCIPAL FINDINGS: We searched PubMed and Cochrane databases (2000-2006) for articles published in English and manually searched bibliographic references. Articles of pharmaceutical randomized controlled trials with weight loss or weight gain prevention as major endpoints were included. Two authors independently reviewed each publication for inclusion. 121 articles met the inclusion criteria. Two authors independently extracted treatment, sample size, drop-out rates, study duration, and statistical method used to handle missing data from all articles and resolved disagreements by consensus. In the meta-analysis, drop-out rates were substantial with the survival (non-dropout) rates being approximated by an exponential decay curve (e(-lambdat)) where lambda was estimated to be .0088 (95% bootstrap confidence interval: .0076 to .0100) and t represents time in weeks. The estimated drop-out rate at 1 year was 37%. Most studies used last observation carried forward as the primary analytic method to handle missing data. We also obtained 12 raw obesity randomized controlled trial datasets for empirical analyses. Analyses of raw randomized controlled trial data suggested that both mixed models and multiple imputation performed well, but that multiple imputation may be more robust when missing data are extensive. CONCLUSION/SIGNIFICANCE: Our analysis offers an equation for predictions of dropout rates useful for future study planning. Our raw data analyses suggests that multiple imputation is better than other methods for handling missing data in obesity randomized controlled trials, followed closely by mixed models. We suggest these methods supplant last observation carried forward as the primary method of analysis
Two-year sustained weight loss and metabolic benefits with controlled-release phentermine/topiramate in obese and overweight adults (SEQUEL): a randomized, placebo-controlled, phase 3 extension study123
Background: Obesity is a serious chronic disease. Controlled-release phentermine/topiramate (PHEN/TPM CR), as an adjunct to lifestyle modification, has previously shown significant weight loss compared with placebo in a 56-wk study in overweight and obese subjects with ≥2 weight-related comorbidities
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Weight Regain After Bariatric Surgery: Scope of the Problem, Causes, Prevention, and Treatment
Purpose of reviewAlthough bariatric surgery is the most effective treatment of severe obesity, a proportion of patients experience clinically significant weight regain (WR) with further out from surgery. The purpose of this review is to summarize the prevalence, predictors, and causes of weight regain.Recent findingsEstimating the prevalence of WR is limited by a lack of consensus on its definition. While anatomic failures such as dilated gastric fundus after sleeve gastrectomy and gastro-gastric fistula after Roux-en-Y gastric bypass can lead to WR, the most common causes appear to be dysregulated/maladaptive eating behaviors, lifestyle factors, and physiological compensatory mechanisms. To date, dietary, supportive, behavioral, and exercise interventions have not demonstrated a clinically meaningful impact on WR, and there is limited evidence for pharmacotherapy. Future studies should be aimed at better defining WR to begin to understand the etiologies. Additionally, there is a need for non-surgical interventions with demonstrated efficacy in rigorous randomized controlled trials for the prevention and reversal of WR after bariatric surgery