Why underweight babies become obese: Study says disrupted hypothalamus is to blame

It seems improbable that a baby born underweight would be prone to obesity, but it is well documented that these children tend to put on weight in youth if they're allowed free access to calories. Now, researchers believe they understand why this happens. A new animal model study at UCLA has found that in low-birth-weight babies whose growth was restricted in the womb, the level of appetite-producing neuropeptides in the brain's hypothalamus — the central control of the appetite — is higher, resulting in a natural tendency among these children to consume more calories. "Other studies have shown that neuronal processes that signal the brain to eat were wired differently in the hypothalamus if a hormonal gene, such as leptin, was missing," said the study's lead author, Sherin Devaskar, professor of pediatrics and executive chair of the department of pediatrics at Mattel Children's Hospital UCLA. "What we found is that appetite-producing genes in the hypothalamus are completely programmed toward eating more to make up for the relative decrease in nutrition while in the womb. So the natural tendency for a child born with low birth weight is to eat more and try to catch up in growth. But if this is not curbed, it can result in childhood obesity." The study was undertaken in rodent models that mimicked small human babies.