Childbearing and development of overweight by smoking habit

Nutrition Research Newsletter, Feb, 2005

Within the past three decades, the prevalence of overweight has doubled and more than one-half of U.S. women between 20 yr and 45 yr of age are considered overweight (BMI > 25 kg/[m.sup.2]) and about one-third are obese (BMI > 30 kg/[m.sup.2]). The childbearing years have been identified as a critical life stage for excess weight gain and development of overweight.

Although childbearing has a modest impact on weight gain, it has not been established whether pregnancy triggers excessive fat deposition and development of overweight for certain women. By prospectively examining change in parity and BMI assessed at 2 to 3-year intervals within a 10-year period in the CARDIA Study, the role of childbearing and other known risk factors in the development of overweight may be clarified. Therefore, this recent study determined whether initiation of childbearing is associated with increased risk of becoming overweight among those nulliparous and normal weight and finding the variables confounded and/or modified by this association.

The CARDIA Study is a prospective, multi-center observation study from 1986-1996, which examined subjects at baseline and in follow-up years 2, 5, 7 and 10. The subjects included 998 nulliparous women, age 18-30 years, who were not overweight at baseline. Dietary intake and history of weight cycling were measured at baseline. At each examination, the women were asked about sociodemographic and behavioral characteristics including cigarette smoking habit, marital status and employment and anthropometric data were obtained.

One hundred and seventy-five black and 183 white women became overweight during follow-up. The incidence rates of overweight according to parity differed by cigarette smoking habit. One and 2 births vs. O, respectively, were associated with increased risk for development of overweight among never smokers and decreased risk among current smokers. Black women were 3.5 times more likely than whites to become overweight and adjusted risk of becoming overweight was increased by 65% to 120% with high school education or less, decreased by one-third for the highest physical activity quartile vs. the lowest, and increased by 45% for two or more weight cycling episodes vs. none at baseline.

Childbearing contributes to development of overweight in non-smokers but not in smokers, where development of overweight is less likely in women who bear children. Race, education and behaviors are other important factors in development of overweight in young children. Development of overweight after a first birth may be related to either a biological susceptibility to excess fat tissue deposition during pregnancy, significant changes in lifestyle accompanying childbearing responsibilities, or other factors, including hormonal changes that are primarily influenced by a first birth.

Erica P. Gunderson, Charles P. Quesenberry, Jr., Cora E. Lewis et al., Development of overweight associated with childbearing depends on smoking habit: The Coronary Artery Risk Development in Young Adults (CARDIA) Study, Obesity Research 12(12): 2041-2052 (December 2004) [Address correspondence to Erica P. Gunderson, Division of Research, Kaiser Permanente, 2000 Broadway, Oakland, CA 91612. E-mail: epg@dor.kaiser.org]