The present study indicates that HFD-induced obesity in rats occurs concomitantly with major changes in transcription factors like elevated mRNA expression of PPARγ in adipose tissue and its target genes FAS, Fab-4 and activation of the proinflammatory factor TNF-α; the effects of inflammation in adipose tissue are not limited to insulin signaling alone. Here, TNF is linked to obesity due to melanocortin 4 receptor deficiency.