In this weight-loss intervention RCT, there were no significant differences among the arms in diet, physical activity, or weight change from baseline to 1-month post-intervention. The trial was successful at recruiting and maintaining contact with participants. It had a relatively large sample size, particularly for a postpartum weight-loss trial,38
and enrollees maintained involvement through the 12-month postbaseline assessments. Additional strengths of the study include a comprehensive and standardized assessment battery, and a diverse population.
Participation in the intervention components that were offered, however, was lower than expected. This raises concerns about the ability of women in this challenging, transitional period of life to attend classes or other group-format interventions while caring for an infant. It was encouraging that weight change in the intervention group was associated with number of classes attended, but this relationship was confounded by underlying factors such as education, race, and income. Class attendance was likely a proxy for having the financial resources and social support to help balance the women’s own needs with the demands of infant care.
Six prior weight-loss trials were identified that were conducted among women in the postpartum period.38–40
Three of these were primarily focused on the effect of diet, exercise, and weight loss on lactation performance.38
In one of the studies,39
health-behavior counseling for weight loss delivered by nurses at the newborn’s preventive health clinic visits showed no effect on behavior changes or weight loss. Two other studies20,41
were most comparable to the current study in that they were RCTs with a focus on postpartum weight loss in a community setting.40
Both resulted in greater weight loss among intervention subjects, but neither found group differences in diet and physical activity.
These latter two studies had much smaller sample sizes (n
=90 and n
=40, respectively) and lower rates of follow-up participation among those few participants. These studies also targeted women with lower BMIs; mean BMI at baseline in both was approximately 30, as compared to 33 in the current study. Also, their participants were almost exclusively white. Black participants in the current study (45%) were less likely to lose weight postpartum, a finding that has been noted previously.42–44
The one common element in the two other interventions was the use of food diaries for self-monitoring, which have been shown to aid in weight loss.45,46
Although the AMP intervention also encouraged the use of self-monitoring tools, both for diet (e.g., diaries, calorie equivalencies) and physical activity (diaries, pedometers), these were not required and results were not systematically reported to the study staff.
As in the AMP trial, women in one of these two studies20
had difficulty attending the weekly group sessions required of the structured intervention group, and more than 40% of participants dropped out, as compared to 27% in the other, which was a mail-based intervention.41
These findings indicate that mail- or other home-based interventions are likely to be more manageable for postpartum women than class-based interventions outside the home.47
It is possible that the measures of behavioral change used may have had limited sensitivity in postpartum women.20,41
Recall methods such as the NDS-R are considered the gold standard for self-reported dietary intake, but did not show significant changes by group in the current study. However, weight also did not change significantly by group, and both the diet and weight measures showed similar, nonsignificant reductions by group. It can be argued that the NDS-R provided an accurate measure of change in caloric intake that is reflected in the resulting weight change, the only issue being that neither caloric intake nor weight was significantly affected by the intervention.
The PAR measure of physical activity is also widely used, but it did present certain limitations. It is based on self-report, and especially in women with small children to care for, the instructions for assessing “moderate” intensity may lead to over-reporting of this type of activity.48
The excessive amount of moderate activity reported by AMP participants (up to 8 hours a day every day of the week) led us to use in the analyses only the “hard” and “very hard” categories, which were meant to reflect intentional leisure-time activity and not everyday household duties.
Maintaining healthy weight is a challenge for most Americans.49
The presence of a newborn in the home makes it especially hard for postpartum women to prioritize their own health behavior efforts; at this time, the child’s well-being is the primary and often overwhelming concern. Previous research among postpartum women,14,15
and a pilot study for the current trial,21
indicated a desire for social support in weight loss efforts. Further, enthusiasm for the program was evident in the relative ease of completing enrollment and the initial level of interest among those enrolled. Attendance was made as easy as possible by providing sessions multiple times a week, at various times during the day and evening and on weekends, and scheduling physical-activity and nutrition sessions back-to-back so that with one effort, mothers could attend two classes. Despite these efforts, and the women’s own motivation and interest, the realities of getting to class with a baby simply overwhelmed many participants.
Future weight-loss interventions in the postpartum period should shift away from group formats, whose limitations outweigh their potential benefits in the form of social support, to home-based options using mail, telephone, or Internet/e-mail. Approaches to increasing social support in such programs could be to enroll women in pairs, as has been shown to enhance weight loss in other studies,26
or to enroll them with their spouses, in order to encourage partners to actively support the new mothers’ weight-loss efforts.50