1. Association between feeding style and weight gain in infants aged 2-7 months Mihrshahi S* 1,2, Daniels L A 1,2, Jansen E 1,2, Battistutta D 2, Wilson JL 1,2, Magarey A 3. 1 School of Public Health, Queensland University of Technology, Brisbane, Australia 2 Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia 3 Nutrition and Dietetics, School of Medicine, Flinders University, Adelaide, Australia * telephone: +61 7 3138 6171 email: seema.mihrshahi@qut.edu.au Background Rapid weight gain during infancy has been associated with obesity in later childhood. Feeding on demand is postulated to support an infant’s innate capacity to respond to hunger and satiety cues and may promote later self-regulation of intake and promote healthy weight gain. When caregivers have control of intake, for example when an infant is bottlefed, the infant’s capacity to self regulate intake may be compromised 1. Formula fed infants are less likely to be fed on demand 2, which may in turn reduce their capacity to self regulate. Our aim was to examine whether feeding style (on demand vs. on schedule) is associated with excess weight gain in infancy. Methods Participants: 698 first time mothers and their infants enrolled in NOURISH, a randomised controlled trial evaluating an intervention to promote positive early feeding practices. Inclusion criteria: healthy infants >35 weeks gestation; no diagnosis that may affect normal feeding and growth. Study design: prospective cohort study with measurements taken twice: at birth and baseline assessment when infants were 2-7 months of age, prior to randomisation. Data collection: birthweight taken from hospital records. Baseline assessment included measurement of infant and mother weight and length/height, and self completed questionnaire for mothers. Statistical analysis: infants were categorised as feeding on demand, to schedule or mixed feeding style, based on responses to questions in Box 1. Weight-for-age z-scores were calculated using WHO standards. The primary outcome was excess weight gain defined as a positive difference in baseline minus birth weight-for-age z-score which indicated tracking above weight percentile. Covariates included gender and age of child, feeding mode (formula feeding/breastfeeding or combination), solid food feeding, maternal age, education and BMI. Bivariate analysis was performed using chi squared tests. A multivariable logistic regression model was used to evaluate the association between feeding style and weight gain. Box 1 Feeding Mode: How are you currently feeding your baby? Breastfeeding exclusively (no other foods or fluids) Breastfeeding fully, with occasional water and juices Combination feeding (breast and formula feeding) Formula feeding only Feeding Style 3 : Do you let your baby feed whenever s/he wants to? Never, Rarely, Sometimes, Often, Always Do you only allow your baby to feed at set times? Never, Rarely, Sometimes, Often, Always Results Data from a total of 612 (88%) infants with a mean age of 4.3 months (SD 0.98 months) were available. The remaining 86 participants had missing data on feeding style, mode or one of the important covariates and so were not included in the analysis. Demographic data: the main demographic characteristics of the population in the study and those with missing data are shown in Table 1. Women who were excluded were significantly younger and had a lower educational attainment than those in the study. Feeding mode: 50% of infants were exclusively breastfed, 8% were fully breastfed and 26% were formula fed and 16% were fed a combination of breastmilk and formula. Feeding style: 61% were fed on demand, only 10% were fed on schedule and 29% had a mixed feeding style. There was a significantly higher proportion of breastfed infants who were fed on demand (Figure 1). Results Table 1: Demographics of the study sample (N=698) Conclusions There was a statistically significant association between feeding on schedule and excess weight gain and formula fed infants were more likely to be fed on schedule. A potential implication of these results is that formula fed babies, who are more likely to be fed on schedule, may be less able to self regulate their energy intake. This effect may persist to later childhood and increase the risk of obesity. This cohort will be followed up until the age of 2 years where the effects of these variables on weight gain will be studied further. References 1.Li R, Fein SB, Grummer-Strawn LM. Do infants fed from bottles lack self-regulation of milk intake compared with directly breastfed infants? Pediatrics. 2010;125:e1386-93. 2.Bartok CJ, Ventura A. Mechanisms underlying the association between breastfeeding and obesity. Int J Pediatr Obes. 2009;4:196-204. 3.Baughcum AE, Powers SW, Johnson SB et al. Maternal feeding practices and beliefs and their relationships to overweight in early childhood. J Dev Behav Pediatr. 2001;22:391-408. CharacteristicIncluded (n=612)Excluded (n=86) Infant Birthweight (kg ± SD)3.5 ± 0.4 Age at baseline (months ± SD)4.3 ± 1.04.5 ± 1.0 Male gender, n (%)305 (49.8%)39 (45.3%) Maternal Age* (years± SD)30.3 ± 5.228.6 ± 5.7 Tertiary education*, n (%)365 (59.6%)41 (47.7%) BMI (kg/m 2 ), n (%) Normal (<24.9) 313 (51.1%)36 (44.4%) Overweight (25.0-29.9) 193 (31.7%)24 (29.6%) Obese (≥30) 103 (16.9%)21 (25.9%) Smoking before or during pregnancy, n (%) 71 (11.6%)14 (16.7%) Change in weight: 410 infants (67%) had a negative or no change in z- score from birth and 202 (33%) had a positive change. A total of 52 (8%) had a difference in z-score above 1. Associations with excess weight gain: After controlling for gender of the child, maternal age, education and smoking, the only factors that showed a statistically significant association with positive weight change were lower maternal BMI, formula feeding and feeding on schedule (Table 2). Adjusted OR (95% CI) P value Maternal age (years)*1.02 (0.98-1.05)0.34 Tertiary education vs. Pre-tertiary0.90 (0.60-1.30)0.55 Maternal BMI (kg/m2)*0.96 (0.93-0.99)0.03 Smoking, Yes vs. No1.51 (0.83-2.77)0.18 Male vs. Female gender (child)1.27 (0.90-1.80)0.18 Formula feeding vs. Breastfeeding/combination1.72 (1.15-2.57)0.008 Feeding on schedule vs. Feeding on demand/mixed1.84 (1.04-3.27)0.04 Solid food, Yes vs. No1.27 (0.88-1.85)0.20 *p <0.05 * Continuous variables Table 2: Odds ratios for the association between feeding style and excess weight gain: mutually adjusted for other variables in model Figure 1: Differences in feeding style between formula fed and breastfed/ combination fed infants (error bars show 95% CIs)