Low-Birth-Weight & Obesity Link

About 10 percent of babies in the United States are born with a low-birth-weight, which is defined as less than the 10th percentile by weight for a given gestation period. Some health organizations define low-birth-weight as less than 2,500 grams (5 pounds, 5 ounces) at term. Low-birth-weight can be caused by a variety of factors including: malnutrition, illness or infection, a reduction in placental blood, smoking, or use of drugs or alcohol during pregnancy. It seems unlikely that a baby born underweight would be predisposed to becoming obese, but research has shown that low-birth-weight babies are likely to put on extra weight in childhood if they’re allowed free access to calories. Now, researchers from UCLA believe that they understand why this happens.

The researchers used rodent models to look at the effects of growth restriction during gestation. After restricting the pregnant rodent’s diet to produce low-birth-weight offspring, the researchers examined their babies at an early age to see how much milk they consumed and to monitor their energy expenditure. After the babies were weaned, they also looked at the effect that being growth-restricted in the womb had on hypothalamic neuropeptides (small proteins that control appetite in the hypothalamus area of the brain). The researchers found that the neuropeptides that are associated with increased appetite and decreased energy expenditure were increased in the hypothalamus (the central control of the appetite), while the neuropeptides that reduce appetite and increase energy expenditure were decreased. As a result, the homeostatic balance of appetite-controlling neuropeptides was disrupted. The hypothalamus was ready to intake as many calories as possible, with no sense of satisfaction.

The researchers concluded from their study that in low-birth-weight rodents, the level of appetite-producing neuropeptides in the hypothalamus region of the brain is higher, resulting in a natural tendency to consume more calories. “The study confirms our hypothesis of how the hypothalamus is involved in weight gain and how weight loss surgery works, said Dr. Terry Simpson, expert weight loss surgeon in Arizona. “With weight loss surgery, we affect the signals that the hypothalamus gets from food. The signal is amplified by the pressure of the band or from the gastric bypass or sleeve or plication,” Dr. Simpson concluded. The researchers will next study how to reverse the hypothalamic neuropeptide changes that cause the central control of appetite to be set too high.

Related Reading: Air Pollution Exposure During Pregnancy Linked to Childhood Obesity

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