Poor diet during pregnancy increases risk of child being obese

It is common knowledge that a well balanced diet in pregnancy is crucial, but now scientists say they believe a poor diet during pregnancy appears to raise the chances of having an obese child.

Researchers at Kyoto University have found that in mice, the offspring of underfed mothers experience a premature surge of the appetite-controlling hormone leptin shortly after birth, and they believe this surge remodels key brain circuits, disrupting the way the body regulates energy intake.

This new discovery adds to existing data which shows that pre-natal under-nutrition does have a long-term impact on many disease states.

Leptin, a hormone produced by fat, appears to play an important role in keeping food intake and energy expenditure in balance, so weight is maintained at a steady level, and is released when a person has eaten enough food to meet their needs, suppressing appetite and producing the feeling of fullness.

It does this by bonding with receptors in an area of the brain called the hypothalamus.

It has been found that injections of the hormone given to morbidly obese people have helped them to shed weight, but other research has shown that some obese people appear to be resistant to the hormone's effects, despite having high concentrations in their bloodstream.

Research suggests 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 this latest study, mice born of mothers who ate 30% less than normal were small at birth and had less fat, but, the under-nourished newborns caught up with the 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 also 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.

The researchers found that when they 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 says their findings suggest 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, agrees and says the theory is very feasible, and reflects a lot of data which shows that prenatal under-nutrition does have a long-term impact on many disease states.

Langley-Evans says animal studies had shown that the pre-natal diet had a profound impact on later eating behaviour.

As an example, rats fed a low protein diet in the womb showed a heightened desire to eat fat, and other research has shown that a low protein diet leads to changes in the density and type of cells in the hypothalamus.

The study is published in Cell Metabolism.