Everything You Know Is Still Wrong, Part 5

Owen, fiercely eating

Sometimes it seems like research is just one big landscape of shifting sands. A unit of knowledge that seems airtight can be reversed within months. Another possibility is for empirical evidence to be conclusive, but nobody is quite sure what it’s conclusive of. For example, here is an intriguing paragraph from MedicalXpress.com:

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.

Mattel Children’s Hospital in California was the place, and Dr. Sherin Devaskar was the lead author of a study whose results were published in the Journal of Neuroscience Research. The subjects were not human infants, but “rodent models that mimicked small human babies.” It has to be done this way because intentionally allowing a human fetus to suffer from malnutrition would be totally unethical, so that limits the options.

Inadequate nutrition is not the only reason for a baby to have low birth weight. If the mother smokes cigarettes, or uses alcohol or drugs, or has an infection or illness, a baby can be born at a weight that is considered dangerous. But it is not only a matter of pounds and ounces. This is where the new understanding comes in. It’s all about disruption of the “homeostatic balance of appetite-controlling neuropeptides,” which causes the hypothalamus to get all mixed up and forget how to experience a sense of satisfaction. In other words:

Growth restriction before birth may cause lasting changes in genes in certain insulin-sensitive organs like the pancreas, liver and skeletal muscle. 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… 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.

And then there is the matter of blood pressure, where an example of “dueling experts” can be found. What’s up with the apparent contradiction? A United Press International story last summer reported:

Pediatric hypertension-related U.S. hospitalizations nearly doubled from 12,661 in 1997 to 24,602 in 2006, researchers found. Lead author Dr. Cheryl Tran of the University of Michigan in Ann Arbor and colleagues used data on discharge records from the Healthcare Cost and Utilization Project Kids’ Inpatient Database, from 1997, 2000, 2003 and 2006. Tran and colleagues hypothesize the increasing hospitalizations may be due in part to the rise in childhood obesity.

The title of that story was “Kid hypertension hospitalizations double.” In the same month, another headline appeared from an equally reputable source — “Despite obesity rise, kids’ blood pressure dipped: U.S. Study.” This Reuters story said:

Researchers at the U.S. Centers for Disease Control and Prevention (CDC) found that while the obesity rate among children in the state of Louisiana nearly tripled between 1974 and 1993, their blood pressure actually improved a bit. Among nearly 11,500 children and teens assessed over the 20 years of the study, which appeared in the journal Pediatrics, the rate of obesity rose from 6 percent to 17 percent. But blood pressure, on average, remained fairly stable.

The current study cannot show the reason why blood pressure didn’t rise along with obesity. In theory, it could have something to do with improvements in early childhood nutrition, such as rising breastfeeding rates – but that is just speculation at this point.

Your responses and feedback are welcome!

Source: “Why underweight babies become obese: Study says disrupted hypothalamus is to blame,” MedicalXpress.com, 05/02/12
Source: “Kid hypertension hospitalizations double,” UPI.com, 06/19/12
Source: “Despite obesity rise, kids’ blood pressure dipped: U.S. Study,” Reuters, 06/06/12
Image by slopjop (Clay Junell).

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