This is the first study to show that both mothers' and fathers' weight gain are affected by the number of children they have, writes lead researcher Haoling H. Weng, MD, with Duke University Medical Center. Her study appears in the current issue of the Journal of Women's Health.
Numerous studies have pointed to changes associated with pregnancy as a factor in women's weight gain problems. Many physiological changes that occur during pregnancy -- including hormonal changes and tendency to accumulate fat -- can persist for years after childbearing, writes Weng.
But what about fathers? Only a few studies have looked the effects that children have on their weight gain.
In this study, Weng and colleagues reviewed lifestyle data on 4,523 couples, all about 56 years old. The couples had an average of four children each. As for their lifestyles, 75% reported they got vigorous activity up to three times a month; 25% were smokers, and 61% drank some alcohol.
The obese women had a significantly lower household income, less education, less insurance, and they were often not employed. They were more likely to be African-American or Hispanic. They also had more children than women without weight problems.
Obese men had more children; they were also younger, African-American, and poorer than non-obese men. The obese men exercised and smoked cigarettes less frequently than the non-obese men.
After researchers took lifestyle factors into account, the number of children had the biggest impact on both mother's and father's obesity, reports Weng.
Among women, each additional child brought a 7% increased risk of obesity, reports Weng. "Among men, a 4% increase in risk of obesity was noted for each additional child," she writes.
"This suggests that a substantial portion of the effect of obesity related to parenthood has to be social, cultural, or psychological," Weng writes.
Weight gain may result from eating more, getting less physical activity, or both, she writes. "Couples with many children have little time to focus on resuming health behaviors that promote weight loss."
SOURCE: Weng, H. Journal of Women's Health, Jan/Feb 2004: vol 13; pp 85-91.