Educational Intervention To Modify Bottle-Feeding Behaviors Among Formula-Feeding Mothers in the WIC Program: Impact on Infant Formula Intake,Weight Gain, and Fatness

Year: 2005

Research Center: Department of Nutrition at the University of California, Davis

Investigator: Dewey, Kathryn G., M. Jane Heinig, and Katie Kavanagh-Prochaska

Institution: University of California, Davis

Project Contact:
Kathryn G. Dewey
Department of Nutrition
University of California
One Shields Avenue
Davis, CA 95616-8669
Phone: 530-752-0851


One of the key factors associated with child obesity is a rapid rate of weight gain during infancy. Infant feeding practices are a major contributor to early rapid weight gain. Formula-fed infants consume more energy and gain weight more rapidly than breastfed infants, even during the first few months of life. Recent evidence indicates the effect of infant feeding on body fatness is long term, with children and adolescents who were breastfed being 20-30 percent less likely to be overweight than children who were formula fed. The mechanisms underlying these differences are not well understood. One possibility is that the composition of infant formulas has a stimulatory effect on intake and growth, although recent data from one of our own studies suggest that neither the protein content or quality, nor the potential renal solute load of formula, is the trigger. Another possibility is that bottle-feeding, not the composition of the milk in the bottle, is more important. One hypothesis is that infants are born with the ability to self regulate their energy intake. The bottle-feeding caregiver may miss the infant’s satiety cues or encourage the infant to empty the bottle.

The objective of this study was to evaluate whether formula-feeding caregivers who are encouraged to be more sensitive to their infants’ satiety cues and to adopt feeding practices similar to those of breastfeeding mothers will in fact alter their feeding practices. The study further examined if this action results in a lower volume of formula consumed at 4 months of age and less rapid weight gain from 1-4 months of age.

This project was a double-blind, randomized educational intervention trial with exclusively formula-feeding caregivers in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) in Sacramento County. Some of the ideas for this intervention were the result of focus groups conducted with WIC mothers in spring 2003, which revealed that overfeeding formula-fed infants is common in this population.

The intervention group received education that promoted awareness of early satiety cues and discouraged the use of large bottles (greater than 6 ounces) before 4 months of age. The control group received standard nutrition education regarding introduction and feeding of solid foods. After initial screening, caregivers completed a baseline 2-day formula intake record and were then randomized to attend either the intervention or control nutrition education class. Subjects were stratified by infant sex and maternal language (English or Spanish) and were randomized using computer-generated stratified random lists with a block size of four. All subjects who attended the class were then followed for no less than 2 months post-class. Formula intake records were again completed at 2 weeks post-class and at approximately 3.5 months of age. At baseline and at about 4 months of age, infant anthropometry was completed. To identify underdilution or over-dilution of formula, caregivers were asked to provide samples of prepared formula at baseline and at the end of the study.

Of the 836 caregivers screened at the 2 clinic sites, 214 were eligible and 104 were willing to participate in the study. The most common reason for refusal was lack of time. Barriers to participation included lack of transportation to the nutrition education class, uncertainty about ability to attend the class, and family or personal problems. Of the 104 women who agreed to participate, 101 completed the baseline questionnaire and 61 completed the first formula intake record. The remainder (n=43) did not complete the baseline intake record and therefore were not included in the randomized trial. In most of these cases, the research staff was never able to reconnect with the caregivers, even after multiple attempts.

Of the 61 caregivers who completed the first intake record and were randomized, 17 never attended the nutrition education class (16 had been scheduled for the class but did not show up even after repeated rescheduling). Of the 44 caregivers attending the nutrition education class, 40 caregivers completed the final formula intake record and 38 of these attended the final measurement session. Among the 40 caregivers who completed the final intake record, no significant differences emerged between intervention and control groups in maternal age, education, body mass index, number of children or ethnicity, or infant birth weight, sex, or formula intake at baseline.

Differences between groups were not significant in formula intake at the second record or at the end of the study, even after controlling for infant age at baseline, baseline intake, sex, birth weight, and time in the study. No significant differences emerged between groups in bottle-feeding behaviors at baseline or at the final intake record, including the mean percentage of bottles emptied, the percentage of subjects who emptied the bottle at more than 50 percent of feedings, and the percentage of bottles offered that were greater than 6 ounces. Bottle-emptying increased in both groups over time (from 50-60 percent of feedings), as did the use of bottles greater than 6 ounces (from less than 5 percent to about 17 percent of subjects).

Differences were not significant between groups in infant weight, length, or sum of skinfold thickness at baseline, after controlling for age and sex. However, by the end of the study, infants in the intervention group were heavier and longer than those in the control group, even after controlling for age at measurement, sex, baseline weight or length, and time in study. In addition, the sum of skinfold thickness was greater among infants in the intervention group than in the control group after controlling for age at measurement one, time in study, sex, and sum of skinfold thickness at baseline.

Response to the nutrition education class, followup phone call, and the key messages was overwhelmingly positive. Most caregivers in the intervention group could accurately repeat the key messages and the demonstrations used to transmit them and felt that they were easy to comply with and to share with friends and family. However, this response did not appear to translate into behavioral change.

The adult learning technique used for this intervention was designed for use in a group setting, but 95 percent of the classes were conducted with just one caregiver because of no-shows. Although the caregivers seemed to appreciate the one-on-one nature of the classes, the lack of group facilitation may be one reason for not achieving changes in feeding practices. Other possibilities include (1) inadequate reinforcement of messages, (2) insufficient depiction of and/or practice with identifying satiety cues in human infants, (3) not intervening early enough in the feeding relationship to support and foster inherent infant self-regulation, (4) not following caregivers long enough to detect a potential change in bottle-feeding behaviors, and (5) other barriers to responsive feeding related to the desire for infants to cry infrequently and sleep more.

In summary, the results of this study indicate that formula intake by infants in this population are quite high—probably reflective of overfeeding—and that modifying bottle-feeding behaviors to prevent overfeeding is a challenging task. The more rapid growth of infants in the intervention group is difficult to explain, given that differences were not significant in the intake variables. The final sample size was quite small, and caregivers participating in the project were not representative of the WIC population in general, which limits the conclusions that can be drawn. However, even though caregivers did not report a difference in intake or bottle-feeding behaviors, the educational intervention was successful in improving knowledge and awareness of the key messages.