Ideal Body Weight

Demographic and clinical information was extracted from the medical record. We identified a patient’s weight nadir, defined as the lowest weight achieved at least 10 months after surgery without coexisting debilitating illness or use of weight-lowering medications. One-year weight was defined as the weight measurement closest to 12 months and within the range of 10–14 months after surgery. Post-operative weights were available for 846 patients (83.3%). Chart-derived nadir weights were validated by telephone interviews in a subset of patients (n=306); there was a 94% concordance between these two sources. Diabetes diagnoses were extracted from patient charts and defined as the presence of any of the following: documentation of diabetes, a fasting glucose measurement ≥ 126 mg/dL, or the use of the anti-diabetes medications insulin or metformin.
Weight loss was characterized at one year and at weight nadir using seven different metrics (Table 1). Residuals were calculated by regressing postoperative BMI (the dependent variable) on preoperative BMI (the independent variable) and outputting the residuals from this model. Because residuals derived from regressing postoperative BMI on preoperative BMI are orthogonal to preoperative BMI, we used these residuals as the benchmark of independence from preoperative BMI. WL characterized by the number of pounds lost was calculated by subtracting the patient’s final weight from his or her baseline weight. As BMI is a function of weight and height, and height is almost always stable over the course of a weight loss study, BMI lost and pounds lost are closely similar methods for measuring weight loss. Percent weight loss (%WL) was calculated by dividing the absolute pounds lost by the patient’s initial weight and is statistically interchangeable with percent BMI change. Percent excess body weight loss (%EBWL) was calculated by dividing the difference between initial BMI and final BMI by the difference between initial BMI and a “normal” target BMI. A BMI of 25 kg/m², the upper limit of a “normal” BMI, is frequently used as the target, but other standards, including race-specific BMI standards or other “ideal weights” according to the Metropolitan Life Insurance Company life tables, may also be used to represent “normal.” In this study, %EBWL was calculated using a reference normal BMI of 25 kg/m². Using this definition, a patient with a BMI of 35 kg/m² has 10 “excess” BMI points, and if this patient were to achieve a BMI of 30, 25, or 20 kg/m² through weight loss intervention, he or she would have lost 50%, 100%, or 150% of his or her excess weight, respectively.

The SR+/− construct was bred to a C57BL/6 background for at least 7 generations before SR+/− parents were bred to produce SR−/− and WT offspring. The ratio of SR−/−, SR+/− and WT offspring resulting from heterozygote crosses did not deviate significantly from the expected 1:2:1 ratio. SR−/− and SR+/− animals were grossly normal, with normal body weight, appearance, grooming, and neurological reflexes. Animals were maintained on a 12h:12h light/dark cycle and provided with food and water ad libitum. Fifteen male and fifteen female animals of the SR−/− and WT genotypes were tested in behavioral assays at 7-12 weeks of age in the following sequence: locomotor activity, rotarod, PPI, water maze. The experimenter (ACB) was blind to genotype when conducting the experiments.