Two health behavior variables were positively and independently associated with IL-6 levels: current obesity (β = + 0.27, P = 0.0003) and tobacco consumption (β = + 0.43, P = 0.001 for former users; β = + 0.51, P = 0.0004 for current users). This evidence concerns the gene IL6 and obesity due to melanocortin 4 receptor deficiency.