An individual’s social norms in terms of what they consider acceptable weight are formed during childhood, and are not highly influenced by our later social networks according to the study published online this week in Obesity.

Dr Heather Brown and colleagues investigated the effects of time-constant factors such as genetics and upbringing, and changeable factors, like friends and opportunities for exercise, on the development of social norms regarding weight in children. 

They used data from the Panel Study of Income Dynamics to analyze the correlation in sibling body mass index (BMI) data from 236 adolescent siblings living together, and 838 adult siblings living apart.

Time-constant factors significantly influenced both groups, but only the adolescent group was influenced by changeable factors. A larger study may provide findings that are more robust.

The authors conclude that previous studies may have overestimated the effect of social networks on BMI and Dr Brown and colleagues suggest that if obesity prevention strategies are to be effective, they should be implemented in early childhood and at a household level.

Reference: Exploring the Factors Contributing to Sibling Correlations in BMI: A Study Using the Panel Study of Income Dynamics DOI: 10.1038/OBY.2011.351

(Press release adapted from Nature)