Molecular insights into the regulation of energy intake and expenditure.

The maintenance of a precise caloric equilibrium is one of the most closely regulated parameters, as illustrated by the calculation that a positive energy balance of only þ0.3% over 30 years would lead to an increase in body weight of over 20 kg. Hence, the caloric input (i.e. appetite) and energy expenditure must be tightly regulated processes. The recent elucidation of the role of the melanocortin-4 receptor (MC4-R) and the cloning of the uncoupling protein 2 (UCP-2) gene have broadened our molecular understanding of the regulation of energy intake and dissipation respectively.