Underweight infants are prone to obesity and UCLA researchers now believe they understand why this happens. Their study, in the Journal of Neuroscience Research, found that in low-birth-weight babies, the level of appetite-producing neuropeptides in the brain's hypothalamus is higher, resulting in a natural tendency to consume more calories.
About 10 percent of babies in the United States are born "small," usually defined as less than 2,500 grams (5 pounds, 5 ounces) at term. Low birth weight can be caused by mothers' malnutrition, illness or infection, a reduction in placental blood, smoking, or the use of alcohol or drugs.
Growth restriction before birth may cause lasting changes in genes in certain insulin-sensitive organs like the pancreas and liver. Before birth, these changes may help the malnourished fetus use all available nutrients. After birth, however, these changes may contribute to health problems such as obesity and diabetes. The study notes that; "the hypothalamus was poised to consume as many calories as were available, with no sense of satisfaction."
"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," said the study's lead author, Dr. Sherin Devaskar.
Devaskar cautions that because this was a rodent study, the research team do not recommend that mothers of low-birth-weight infants start restricting their children's nutrition, suggesting instead that they consult with a pediatrician regarding any feeding questions.
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Source: University of California - Los Angeles Health Sciences