Doctoral Dissertations

Date of Award

5-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Human Ecology

Major Professor

Jean D. Skinner

Committee Members

Betty Ruth Carruth, Paula Zemel, Charles Thompson, James Moran

Abstract

Change in body mass index from conception to 12 months postpartum (BMIdiff) was studied in 75 white adolescents. Postpartum (PP) body fat was estimated with bioelectrical impedance analysis, and waist to hip ratio (WHR) was measured. The purpose of this study was to examine the relative influence of several variables (including age, gestational weight gain, PP energy and fat intake, dietary restraint, genetic influences, and lifestyle changes) on BMIdiff, and to examine possible relationships between these variables and body composition, including fat distribution. The adolescents were interviewed and actual measurements, including dietary intake, were performed at 12 months PP. Prepregnancy and PP dietary restraint, hunger, and disinhibition were evaluated retrospectively with Stunkard and Messiclds Three-Factor Eating Questionnaire. Mean BMIdiff was +2.11 (±3.56) kg/m, median was +1.43, and values ranged from -6.85 to +11.88. Close to 30% of the girls experienced decreases in BMI, and 31% remained within 1 unit of their BMI at conception. Multiple linear regression modeling was used to estimate the relative influence of the studied variables on BMIdiff and/or weight change (Wtdiff). In most models, gestational weight gain was the strongest predictor, explaining as much as 46% of the variation in Wtdiff. Kcal/kg/day (dietary intake) was the strongest predictor in some models, including one model with an R2 of 0.82, in which the partial R^ for kcal/kg/day was 0.50. Gestational gain (+), socioeconomic status (-), gynecological age (-), and oral contraceptive use (-) were the other significant predictors. Postpartum kcal/kg/day were negatively related to BMIdiff, as were kcal/day. In models which included interaction between gestational weight gain and weight at conception, the interaction variable was the strongest predictor, explaining as much as 53% of the variation in BMIdiff. PP smoking (-), PP dietary restraint (+), and WHR (+) were other significant predictors for the entire data set. For those with normal BMI at conception, PP smoking was not a significant predictor, but prepregnancy weight loss attempt (+) was significant. The following variables were not significant predictors of BMIdiff or Wtdiff in any of the models tested: PP kcal/day (dietary), % kcal from fat, PP activity levels, breastfeeding, major changes in school/work or marital/living arrangements. Percent body fat (%BF) at 12 months PP was significantly correlated with BMIdiff (r=0.67, P=0.0001). Gestational weight gain explained 17% of the variation in %BF. Also, WHR was significantly correlated with PP BMI, %BF, and BMIdiff.

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