NEUROPEPTIDES, THE HYPOTHALAMUS AND OBESITY - INSIGHTS INTO THE CENTRAL CONTROL OF BODY-WEIGHT

Body weight tends to remain relatively stable for long periods over an adult's lifespan. Dieting can reduce weight by 5-10%, but in most ind ividuals attempts to lose larger amounts of weight are counteracted by a reduction in energy expenditure and an increase in hunger. The fact that body weight appears to be actively defended in this manner sugge sts that it is homeostatically regulated at a certain ''set-point''. S uch a mechanism is likely to be centrally controlled by the brain sinc e the hypothalamus can sense the amount of adipose tissue stored in th e body and can alter both energy intake and expenditure. Over the past four years a number of major advances have reinforced the critical ro le the brain may play in controlling body weight, and these have great ly enhanced our understanding of this area. Advances have included the identification of several genetic mutations that cause obesity in ani mal models, examination of the metabolic consequences of such mutation s and the development of mice with genetically engineered altered neur opeptide levels. This review summarises what has been recently discove red about the regulation of body weight by the brain and how this may be disrupted in obesity.