Context matters: Preliminary evidence that the association between positive affect and adiposity in infancy varies in social vs. non-social situations

Authors: WOOD, ALEXIS - Children'S Nutrition Research Center (CNRC); MOMIN, SHABNAM - Children'S Nutrition Research Center (CNRC); SENN, MACKENZIE - Children'S Nutrition Research Center (CNRC); BRIDGETT, DAVID - Northern Illinois University

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2022
Publication Date: 6/9/2022
Citation: Wood, A.C., Momin, S.R., Senn, M.K., Bridgett, D.J. 2022. Context matters: Preliminary evidence that the association between positive affect and adiposity in infancy varies in social vs. non-social situations. Nutrients. 14. Article 2391. https://doi.org/10.3390/nu14122391.
DOI: https://doi.org/10.3390/nu14122391

Interpretive Summary: Up to 16% of infants in the United States have a weight for length that is high enough to put them at risk for obesity. Previously, it was thought that excess weight gain in the first year of life principally arose from how infants were fed by their caregivers (e.g., how much milk was fed, and how often). But more recent research suggests that this is not the case, and that caregiver feeding behaviors are not the primary, or sole, determinant of infant weight. Such new findings suggest the possibility that infants also shape their growth trajectories, but we know little about which infant characteristics increase the likelihood of higher weight gain. This study sought to examine the association between infant positivity (such as how much they smile and laughing) with weight, during the first year of life. We found that four-month-old infants who displayed a lot of positivity during games played with their primary caregiver were lighter at 12 months of age than those who displayed lower levels. Conversely, four-month-old infants who displayed higher levels of positivity during game played with strangers, such as members of our research team, were heavier at 12 months of age than those who displayed lower levels. These findings suggest that emotions, and particularly positive emotions, can predict and perhaps even have an influence on weight changes during the first year of life. However, the context in which the child displays a lot of positivity is important for its relationship to adiposity: the association with later weight is different whether the child shows positivity in the presence of their primary caregiver vs. in the presence of a stranger.

Technical Abstract: Previous studies have suggested that infants high in negative affect have higher levels of adiposity, arising in part via changes in nutrition (e.g., "feeding to soothe"). Few studies have examined whether positive affect shows similar or inverse associations with adiposity. The current study examined cross-sectional and longitudinal relationships between adiposity and observations of positive affect in both a social and a non-social context, using data from infants at four (n=125) and 12 (n=80) months of age. Our analyses did not find any cross-sectional associations between positive affect and adiposity (all p>0.05). However, in the longitudinal analyses, positive affect in a non-social context, when observed at four months of age, was positively associated with weight-for-length at 12 months of age (zWFL; Beta=1.49, SE=0.67, p=0.03), while positive affect observed at four months of age in a social context was inversely associated with body fat percentage at 12 months of age (Beta=-11.41, SE=5.44, p=0.04). These findings provide preliminary evidence that the p positive affect is related to adiposity in infancy and suggest that the direction of association (i.e., direct or inverse) may be specific to the context in which positive affect is measured. Future research should examine the role of nutritional status in any relationships between adiposity and emotion at this early stage.