THE way your brain developed when you were a fetus or baby could determine your bodyweight for the rest of your life.
The culprit is leptin, a hormone whose levels surge after a meal, sending a 鈥渟top eating鈥� signal to the brain. Richard Simerly鈥檚 team at the Oregon Health & Science University in Portland has now shown that in mice at least, the hormone is crucial for normal development of the circuits in the region of the hypothalamus that regulates appetite (Science, vol 304, p 108). Mice with a mutation that makes them leptin-deficient had fewer nerve connections in this area. Restoring leptin levels to normal only these circuits only if it was done during the neonatal period.
These circuits may determine the 鈥渂ody weight set point鈥� that plagues so many dieters. Eating too much or too little during critical periods of development might induce long-lasting changes in these circuits. 鈥淎 lot of people believe changes in weight are due to a willingness to change your lifestyle,鈥� says Jeffrey Friedman, a neuroscientist at Rockefeller University in New York who was part of the research. 鈥淏ut alterations in weight are also due to basic circuits that are beyond inhibitory control. There may be fundamental differences in wiring between the obese and the lean.鈥�
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