Scientists believe they may have discovered why a poor diet during pregnancy appears to raise the chances of having an obese child.
Diet in pregnancy is crucial
Research on mice shows the offspring of underfed mothers experience a premature surge of the appetite-controlling hormone leptin shortly after birth.
Experts believe this surge remodels key brain circuits, disrupting the way the body regulates energy intake.
The research, by Kyoto University, is published in Cell Metabolism.
Leptin is a hormone produced by fat that appears to play an important role in keeping food intake and energy expenditure in balance, so weight is maintained at a steady level.
It is released when a person has eaten enough food to meet their needs, suppressing appetite and producing the feeling of "satiety", or fullness.
It does this by bonding with receptors in an area of the brain called the hypothalamus.
Injections of the hormone given to morbidly obese people have helped them to shed weight.
However, research has also shown that some obese people appear to be resistant to the hormone's effects, despite having high concentrations in their bloodstream.
Evidence has also suggested that a neonatal surge of leptin, which occurs early in the life of newborns, may play an important role in the formation of energy-regulating brain circuits in the hypothalamus.
In the latest study, mice born of mothers who ate 30% less than normal were small at birth and had less fat.
However, the under-nourished newborns caught up with normal mice after 10 days and, when fed a high-fat diet, developed pronounced weight gain and increased leptin levels compared to normal mice on the same diet.
The under-nourished mice had lower body temperatures than normal mice - suggesting they had been programmed to conserve energy.
Analysis showed that the surge in leptin levels occurred six to eight days earlier than normal in the under-nourished animals.
When the researchers mimicked that premature leptin surge by administering the hormone to normally-fed mice, those animals also became prone to obesity upon eating a diet high in fat.
The researchers found premature exposure to a leptin surge seemed to impair the body's ability to transport the hormone around the brain.
They also found these mice were more likely to have abnormalities in the hypothalamus.
Researcher Dr Shingo Fujii said: "The present study suggests that a premature surge of leptin as a result of foetal under-nourishment can alter energy regulation by the brain and contribute to developmental origins of health and disease."
Dr Simon Langley-Evans, an expert in human nutrition at Nottingham University, said: "This theory is very feasible. There is now quite a lot of data to show that prenatal under-nutrition does have a long-term impact on many disease states."
He said animal studies had shown that the pre-natal diet had a profound impact on later eating behaviour.
For instance, rats fed a low protein diet in the womb showed a heightened desire to eat fat.
Other research had shown that a low protein diet led to changes in the density and type of cells in the hypothalamus.