Modelling the propagation of adult male muscle dysmorphia in Spain: economic, emotional and social drivers

Males aged over 40 do more gym practice to improve their body image as a way of reinforcing their personal self-esteem and sexual appeal. Cases when self-image becomes an obsession may result in a body dysmorphic disorder named 'muscle dysmorphia' (MD). The combination of psychological, environmental and biological drivers determines the appearance and development of this disorder. In this article, we developed a discrete population mathematical model to forecast the rate of prevalence of males who are noncompetitive bodybuilders at risk of suffering MD in Spain in forthcoming years. Economic, emotional, sociological and psychological motivations were taken into account to quantify the dynamic behaviour of Spanish noncompetitive bodybuilders. The impact of the unemployment is reflected in the construction of two coefficients, α u and α 21 , which explain subpopulation transits due to the economy. Sociological influences, such as human herding and social propagation, were also considered. Our results predict an increase in Spanish noncompetitive bodybuilders suffering MD from 1% in 2011 to around 11% in 2015. Our model can be applied to any other western country where data are available and to another study period when the hypotheses are applicable.