Extension of high brown fat thermiogenesis and high metabolic rate throughout childhood, and into the adult stage, can prevent the development of diet- and age-induced obesity (66), as evidenced, for example, by the general lack of catch-up growth, obesity, or metabolic syndrome in Silver-Russell syndrome, and the high energy expenditure and lean phenotypes associated with loss of XLαs expression (in contrast to low energy expenditure, obesity, and insulin resistance, with reduced expression of Gsα) (18, 39). Here, GNAS is linked to obesity due to melanocortin 4 receptor deficiency.