@article {Jiang:December 1991:0960-8923:373,
	author = "Jiang, Donald",
	author = "Renquist, Kathleen",
	author = "Mason, Edward",
	title = "Weight Loss Curve Analysis",
	journal = "Obesity Surgery",
	volume = "1",
	year = "December 1991",
	abstract = "The purpose of this study was to develop a mathematical model to describe weight loss trend over time and to determine differences, if any, among various weight loss trends. Weight change was studied following Roux-en-Y gastric bypass (RGB) and vertical banded gastroplasty (VBG). The total number of patients analysed was 3172, 63.5% VBG and 36.5% RGB. Median age (years) for VBG was 36 (range 18-70) and RGB 38 (range 18-66). Median operative body mass index (BMI) (kg/m<SUP>2</SUP>) for VBG was 45.0 (range 30.1-90.5) and RGB 43.3 (range 30.4-80.6). Females represented 87% of the VBG patients and 89% of RGB patients. Obesity category percentages for each operative type were: super--VBG 20%, RGB 14%; morbid--VBG 78%, RGB 80%; obese--VBG 2%, RGB 6%. The development of a mathematical model to study weight loss over time was a two-stage process. First, weight loss trend was determined as evidenced by individual patient BMI values plotted over time. It was observed that plots represented quadratic curves, so the model BMI = B<SUB>0</SUB> + B<SUB>1</SUB>(time) + B<SUB>2</SUB>(time)<SUP>2</SUP> was used. Second, the estimated beta's (B<SUB>0</SUB>, B<SUB>1</SUB>, B<SUB>2</SUB>) were treated as response variables to estimate weight loss trend for the combination effect of three independent variables: gender (male and female), obesity category (super, morbid, obese) and operative type (VBG and RGB). It was found that the three independent variables simultaneously interact with patient weight loss (<I>p</I> = 0.0001).",
	pages = "373-380(8)",
	url = "http://www.ingentaconnect.com/content/klu/os/1991/00000001/00000004/00000057"
	doi = "doi:10.1381/096089291765560755"
}