Kai Ling Kong

Sociodemographic Differences and Infant Dietary Patterns

OBJECTIVES: To identify dietary patterns in US infants at age 6 and 12 months, sociodemographic differences in these patterns, and their associations with infant growth from age 6 to 12 months. METHODS: We analyzed a subsample (760 boys and 795 girls) of the Infant Feeding Practices Study II (2005–2007). Mothers reported their infants’ intakes of 18 types of foods in the past 7 days, which were used to derive dietary patterns at ages 6 and 12 months by principal component analysis. RESULTS: Similar dietary patterns were identified at ages 6 and 12 months. At 12 months, infants of mothers who had low education or non-Hispanic African American mothers (vs non-Hispanic white) had a higher score on “High sugar/fat/protein” dietary pattern. Both “High sugar/fat/protein” and “High dairy/regular cereal” patterns at 6 months were associated with a smaller increase in length-for-age z score (adjusted β per 1 unit dietary pattern score, −1.36 [95% confidence interval (CI), −2.35 to −0.37] and −0.30 [−0.54 to −0.06], respectively), while with greater increase in BMI z score (1.00 [0.11 to 1.89] and 0.32 [0.10 to 0.53], respectively) from age 6 to 12 months. The “Formula” pattern was associated with greater increase in BMI z score (0.25 [0.09 to 0.40]). The “Infant guideline solids” pattern (vegetables, fruits, baby cereal, and meat) was not associated with change in length-for-age or BMI z score. CONCLUSIONS: Distinct dietary patterns exist among US infants, vary by maternal race/ethnicity and education, and have differential influences on infant growth. Use of “Infant guideline solids” with prolonged breastfeeding is a promising healthy diet for infants after age 6 months.

Origins of food reinforcement in infants

BACKGROUND Rapid weight gain in infancy is associated with a higher risk of obesity in children and adults. A high relative reinforcing value of food is cross-sectionally related to obesity; lean children find nonfood alternatives more reinforcing than do overweight/obese children. However, to our knowledge, there is no research on how and when food reinforcement develops. OBJECTIVE This study was designed to assess whether the reinforcing value of food and nonfood alternatives could be tested in 9- to 18-mo-old infants and whether the reinforcing value of food and nonfood alternatives is differentially related to infant weight status. DESIGN Reinforcing values were assessed by using absolute progressive ratio schedules of reinforcement, with presentation of food and nonfood alternatives counterbalanced in 2 separate studies. Two nonfood reinforcers [Baby Einstein-Baby MacDonald shows (study 1, n = 27) or bubbles (study 2, n = 30)] were tested against the babys favorite food. Food reinforcing ratio (FRR) was quantified by measuring the reinforcing value of food (Food Pmax) in proportion to the total reinforcing value of food and a nonfood alternative (DVD Pmax or BUB Pmax). RESULTS Greater weight-for-length z score was associated with a greater FRR of a favorite food in study 1 (FRR-DVD) (r = 0.60, P < 0.001) and FRR of a favorite food in study 2 (FRR-BUB) (r = 0.49, P = 0.006), primarily because of the strong association between greater weight-for-length z score and lower DVD Pmax (r = -0.71, P < 0.0001) and BUB Pmax (r = -0.53, P = 0.003). Infant monthly weight gain was positively associated with FRR-DVD (r = 0.57, P = 0.009) and FRR-BUB (r = 0.37, P = 0.047). CONCLUSIONS Our newly developed paradigm, which tested 2 different nonfood alternatives, demonstrated that lean infants find nonfood alternatives more reinforcing than do overweight/obese infants. This observation suggests that strengthening the alternative reinforcers may have a protective effect against childhood obesity.

Reducing relative food reinforcement in infants by an enriched music experience.

The reinforcing value of food may be established early in life. Research shows that infant weight status is related to the relative reinforcing value of food versus non‐food alternatives (food reinforcing ratio, FRR). The purpose of this pilot study was to assess the effects of a 6‐week music enhancement program (Music Together®, n = 14) versus an active play date control group (n = 13) on the FRR in 9‐ to 16‐month‐old infants who were high in relative food reinforcement.

Impact of a walking intervention during pregnancy on post-partum weight retention and infant anthropometric outcomes.

Few studies have investigated the impact of lifestyle interventions during pregnancy on post-partum weight retention and infant growth. Thirty seven previously non-exercising, overweight or obese pregnant women were randomly assigned to a walking intervention or non-intervention control. For the follow-up study, weight of the mother and weight, length and body composition of the infant were collected at 1 month post-partum (n=37) and 6 months post-partum (n=33). Analysis of variance and linear regression were conducted to determine the differences and association in maternal post-partum weight retention and child outcomes. At 6 months post-partum, weight retention of obese women in the intervention group (Int-OB) was -0.10±8.11 kg; while, obese women in the control group (Con-OB) was 6.35±7.47 kg. A significantly higher percentage of Con-OB women retained more than 5 kg at 6 months post-partum (P=0.046). Even though statistically non-significant between the groups, the growth trend observed among offspring of obese women in the control group was consistently higher than the offspring of obese women in the intervention group from birth to 6-months. Third trimester gestational weight gain rate significantly predicted 6-m weight-for-length z-score after controlling for birth weight, treatment group and pre-pregnancy body mass index (r 2=0.31, β=1.75, P=0.03). The reduced post-partum weight retention observed among the obese women in the intervention group may be explained in part by the lifestyle modification during pregnancy.

Food reinforcement during infancy.

The motivation to eat, as operationalized by measuring how hard someone will work for food, is cross-sectionally and prospectively related to obesity. Persons high in food reinforcement consume more calories, and energy intake mediates the relationship between food reinforcement and obesity. Research has shown avid sucking for milk in early infancy predicts later adiposity, and the relationship between food reinforcement and excess body weight has been observed in infants as young as 9months of age. New methodological developments in studying food reinforcement in infants and young children provide the first opportunity to study the origin of food reinforcement. This review seeks to provide background on the measurement of food reinforcement, and to present, for the first time, prenatal and postnatal predictors of infant food reinforcement. Lastly, potential mechanisms for an increasing trajectory of food reinforcement throughout development are proposed.

Leisure time physical activity before and during mid-pregnancy and offspring adiposity in mid-childhood.

Effects of maternal leisure time physical activity (LTPA) on paediatric obesity are unknown. The objective of this study was to examine associations of maternal LTPA with offspring overall and central adiposity in mid‐childhood.

Glycemic index, insulinemic index, and satiety index of kefir.

Objectives: To determine glycemic, insulinemic, and satiety indices of 3 types of kefir. Methods: This study was divided into 3 phases. In phase 1, 50 g of available carbohydrate from low-fat strawberry kefir or orange kefir was tested, and in phase 2, low-fat plain kefir containing 25 g of available carbohydrates was tested for glycemic index (GI), in both cases compared with an equivalent amount of glucose. In phase 3, 1000-kJ portions of all 3 types of kefirs were compared with white bread with the same energy content to determine the insulinemic index (II) and satiety index (SI) of all 3 kefirs. In all phases, a single-meal, randomized crossover design was performed in which the test meals were given to healthy adults, 5 men and 5 women. Results: The total incremental plasma glucose area under the curve (iAUC) for strawberry, orange, and plain kefirs was significantly lower compared with the respective high-GI control food, which was glucose solution. However, the IIs and SIs of kefir did not differ significantly from the white bread. Conclusion: Kefir is a low- to moderate-GI food; however, its II was high. Although kefir had higher water content, the SI of kefir was not significantly different from white bread.

Food and non-food reinforcement among pregnant women

Excessive gestational weight gain (GWG) in pregnancy may be driven in part by greater motivation to eat, and studying the relative reinforcing value of food versus non-food commodities may provide insight into factors important for excessive GWG. This study was a cross-sectional examination of the relationship between women meeting the Institute of Medicine (IOM) guidelines for GWG and the relative reinforcing value of food vs. non-food commodities during pregnancy. Two-hundred and thirty-three pregnant women (1st trimester, n = 44; 2nd trimester, n = 105; 3rd trimester, n = 84), aged 18-40, were recruited via a crowdsourcing platform and completed an online survey. Relative food reinforcement (RRVfood), relative non-food activity reinforcement (RRVactive) and relative non-food cognitively enriching activity reinforcement (RRVcognitive) were measured by a questionnaire at the point of contact. Self-reports of gestational age and weight gain during pregnancy were collected. The relationship between food and non-food reinforcement was assessed based on IOM classifications for weight gain during pregnancy. After adjustment for womens education level and parity, higher RRVfood (p = 0.036) and lower RRVcognitive (p = 0.040) responses were associated with greater GWG. Food reinforcing ratio (FRR) analysis was then conducted to systematically examine the effect of non-food behaviors on GWG when food reinforcement was accounted for. Women who gained below the IOM weight gain guidelines had significantly higher FRRcognitive than those gaining above (p = 0.013), indicating cognitively enriching activities may better compete with food among pregnant women. Interventions that help to increase the reinforcing value of cognitively enriching activities may be a new avenue to regulate eating to minimize GWG.