Being a last-born child and having a sister have been associated with higher body mass index (BMI). Encouragement to eat that overrides children’s self-regulation has been reported to increase the risk of obesogenic eating behaviors. This study sought to test the hypothesis that encouragement to eat during mealtime from older siblings and sisters mediates associations of being last-born or having a sister with higher BMI.
Children aged 4–8 years (n = 75) were videotaped while eating a routine evening meal at home with one sibling present. Encouragement to eat (defined as direct prompts to eat or general positive statements about food) delivered to the index child (IC) from the sibling was coded from the videotape. Path analysis was used to examine associations between IC’s birth order, sibling’s sex, encouragement counts, and IC’s measured BMI z-score (BMIz).
Being the younger sibling in the sibling dyad was associated with the IC receiving more encouragements to eat from the sibling (β: 0.93, 95 % confidence interval (CI): 0.59, 1.26, p < 0.0001). The IC having a sister compared with a brother was not associated with the IC receiving more encouragements to eat from the sibling (β: 0.18, 95 % CI: −0.09, 0.47, p = 0.20). The IC receiving more encouragements to eat from the sibling was associated with lower IC BMIz (β: −0.06, 95 % CI: −0.12, 0.00, p = 0.05).
Children were more likely to receive encouragements to eat from older siblings than younger siblings. Being the recipient of encouragements to eat from a sibling was associated with lower, not higher, child BMIz, which may reflect sibling modeling of maternal behavior. Future longitudinal studies are needed to examine whether encouragements to eat from siblings lead to increase in BMI over time. Encouragements from siblings may be a novel intervention target for obesity prevention.