FAS and obesity due to melanocortin 4 receptor deficiency: Indeed, a fructose-enriched diet contributes to the risk of MS, IR and obesity, mediated by the activation of the carbohydrate-responsive element-binding protein (ChREBP) transcription factor in synergy with sterol regulatory element-binding proteins-1C (SREBP-1c) to increase the expression of lipogenic genes such as acetyl CoA carboxylase (ACC) and fatty acid synthase 1 (FAS1) [44].