The fat-regulating protein leptin was first linked to obesity more than a decade ago. New research on mice indicates that the offspring of undernourished mothers experience a leptin surge that raises their risk of becoming overweight.

A team of researchers led by Shigeo Yura and Hiroaki Itoh of the Kyoto University Graduate School of Medicine studied mice born to mothers that ate 30 percent less than a group of control animals did. The malnourished mice underwent a premature increase in leptin levels compared to control animals and at birth, the animals were smaller and leaner than their normal counterparts. After 10 days, however, they had gained enough weight to catch up. What is more, when they were fed the same high-fat diet as animals born to well-nourished females, the initially undernourished animals fattened up substantially and maintained increased levels of leptin compared to the controls.

The undernourished mice had lower body temperatures on average than normal animals, which suggests that they were programmed to conserve energy as they developed in conditions with insufficient nutrients. The team also administered a dose of leptin to normal animals, to see if the effects would be the same. "Unexpectedly, normal offspring treated with leptin as newborns were indistinguishable from those that were undernourished before birth," Fujii remarks. "Premature onset of leptin surge is thus casually related to pronounced obesity in undernourished offspring on a high-fat diet." The researchers report their results in the June issue of the journal Cell Metabolism.