Obesity, defined as a body mass index (BMI) of 30 or more, is a preventable disease that results from changes in dietary and physical activity patterns, which in turn can be a consequence of environmental and societal changes. Moreover, according to the World Health Organization (WHO), almost 500 million adults suffer from obesity, and it now ranks as the fifth leading cause of death globally. Any approach that elaborates on the causes and possible treatment strategies for this increasing problem will be welcomed.

In this paper, Marathe et al. use graph theory methods to analyze the impact of friendship networks on individual weight perception, which may be an indicator for the development of obese behavior.

The study is based on the longitudinal data of 20,502 adolescents and young adults, obtained between 1994 and 2002. The authors apply standard structural analysis and multinomial logistic regression analysis to measures such as degree distribution, clustering coefficients, clique size, s-metric, and number of components. This analysis reveals the dynamics of structural changes in friendship networks and the temporal relationships between variables.

The paper explores three main hypotheses:

• “Obesity leads to social marginalization and not vice versa”;
• “People misperceive their weight status”; and
• “Perception of the weight status is more important than the actual weight status in determining weight goals.”

These hypotheses certainly improve our understanding of the social causes of obesity. However, a few limitations in the design of this study may lead to restricted applicability of the results. First, social interactions and individual perceptions may vary by ethnic and cultural background. Consequently, this issue may affect the applicability of hypotheses 2 and 3. Second, considering the explosive growth of Internet-based social networks in the past ten years, and the subsequent changes in friendship definitions and the nature of human interactions, the question arises whether a study that ended in 2002 can accurately reflect modern friendship networks and status developments.

Despite these limitations, scientists will benefit from learning the study’s results. I strongly recommend this paper to scholars interested in the etiology and treatment of obesity and eating disorders.