Breast-feeding has a limited long-term effect on anthropometry and body composition of Brazilian mothers

The effect of lactation on maternal nutrition is controversial. Some studies have shown that breastfeeding reduces maternal weight, whereas some have not. All studies have been restricted to the first 2 y after delivery. We investigated the effect of lactation on maternal nutrition 5 y after delivery. All mothers giving birth in the city of Pelotas, Brazil, in 1993 were interviewed and weighed soon after delivery; information was also obtained on prepregnancy weight. In 1994, information on breast-feeding duration and pattern was collected for a 20% subsample. They were seen again in 1998, and those eligible (nonsmokers, no subsequent pregnancy, last birth weight greater than or equal to 2500 g) underwent measurements for weight, height, waist, hip and arm circumferences, triceps and subscapular skinfolds. The following indices were calculated in 312 women: body mass index, waist/hip ratio, arm fat area, the percentage of body fat assessed through skinfolds, and weight and body mass index change since before conception. The percentage of body fat was also measured through bioimpedance for half of the sample. After adjustment for confounding, all outcomes generally showed a similar pattern, i.e., mothers who breast-fed for 6-11.9 mo had lower measurements than those with shorter or longer durations. However, only the association with bioimpedance was significant (P < 0.03), and that for arm fat area tended to be significant (P = 0.06). Exclusive or predominant breastfeeding at 4 mo was associated with lower waist circumference (P = 0.05) and the percentage of body fat measured through skinfolds (P = 0.04). This study suggests that the relationship between breast-feeding and long-term changes in maternal weight is complex and, in this population, not particularly strong.