Parenthood accelerates weight gain over the life course according to a new study from The University of Texas at Austin.
In a study to appear in Social Science and Medicine, Debra Umberson, professor of sociology at the university, found that adults with children gain significantly more weight over time than those without.
Umberson and her team of researchers analyzed data from a national longitudinal survey, in which they tracked changes in body mass index (BMI) levels (a ratio of height to weight) among 3,617 adults over a 15-year period. They found that by age 55, parents reach an average BMI in the obese zone (over 30) and peak at an average BMI of 31 by their mid to late 60s. But for those without children, the average BMI merely reaches the overweight zone (25 to 29) by age 55.
As part of the study, Umberson and her team of researchers examined how various life-course factors, such as timing of first birth, transitioning into parenthood and living with an adult child, influence weight change over time.
According to the findings, both men and women who have their first child around age 26 to 27 gain the least weight over time. The further away from this age either younger or older the more rapid the weight gain, Umberson says.
Parents who have children at a young age are more likely to be of low socio-economic status, which is associated with increased risk for obesity, Umberson says. And those who have children later in life experience the effects of mid-life weight gain, which averages 3 to 4 pounds a year, along with the lifestyle constrictions of parenthood that further promote weight gain.
While living with a child, men gain even more weight than women. This finding suggests that living with children alters the lifestyles of men even more than for women. Factors that influence weight gain for men include reduced exercise time and a decrease in substance abuse, such as smoking and heavy drinking, Umberson says.
"Parenthood imposes pressure for routine and new responsibilities such as staying sober and healthy to care for children," Umberson says. "Given that smoking and heavy drinking are more prevalent among men, they are more likely to gain weight due to lifestyle behavioral changes."
Although both parents progressively gain weight over time, women gain more while raising more than one child. Umberson suggests this weight gain may be caused by the biological effects of pregnancy added to the daily constraints and responsibilities of parenting.
Umberson says the findings underscore how important it is for both men and women to maintain a healthy weight before and after they have children. This applies especially to those who are overweight or obese at the start of parenthood.
"Although the difference in annual rates of gain between parents and non-parents may not be noticeable in the short-run, these differences appear to become substantial over the course of adulthood," she says.
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