Examination of Possible Explanations for Differential Weight Changes Associated with Pregnancy.

摘要

Pregnancy is a time in adult life when weight gains are considered a sign of health. The recommended weight gain for women in the United States is 25 pounds. Some women, however, gain differential amounts of weight during their pregnancies. Reasons for this differential gain are unknown. Two studies were designed to examine several explanations for differential weight gains suggested in the literature. A human laboratory study of 50 women (38 pregnant and 12 postpartum) was designed to investigate behavioral and psychological variables during all three trimesters and a postpartum period. This study was presented to subjects as a taste perception study to avoid self-conciousness about eating. Food from three taste classes--sweet, salty, and bland--was provided to subjects. Consumption of food from each class, as well as general laboratory food consumption, was measured. Psychological measures, such as restraint, affect, social support, and stress questionnaires, were given to each subject. Women in the second trimester consumed more sweet-tasting food and more calories than did women in any other study period. No subject in the present study gained excess weight, possibly because all subjects were restrained eaters. To avoid psychological influences such as restraint, an animal study using 48 female rats , in 4 groups of 12 was conducted to measure behavioral and biological variables longitudinally across pregnancy. The design crossed pregnancy with type of food available. Body weight and adipocyte number and size, and consumption of laboratory chow, glucose solution, and water were measured daily before, during, and after pregnancy. Pregnant and postpartum rats, with access to both glucose solution and chow, had more adipose tissue than did both nonpregnant controls and pregnant controls provided with only laboratory chow.