How fat cells work.

Health and medicine explained.
May 13 2008 4:06 PM

Your Health This Week

Tantalizing new insight into fat cells. Also, why to eat chocolate while pregnant.

This week, Dr. Sydney Spiesel discusses striking new findings about fat cells, good news about eating chocolate during pregnancy, and evidence on whether taking ibuprofen staves off Alzheimer's.

How fat works

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Question: The masses of fat in our bodies are made up of millions of individual cells called adipocytes. There are two differences between fat stores in obese and in lean people. Obese people have a larger total number of fat cells, and their individual fat cells are larger, plumper, fuller of fat. What is it that controls these differences? Is there, perhaps, a hormone that signals fat cells to multiply as we gain weight or to stop multiplying as we shed pounds? Or maybe fat cells are like brain cells, and we acquire a number of them early on that remains constant in adulthood?

New research: The answer to these questions was a complete mystery until the publication in Nature this month of this new research. The answers it provides may result in an entirely new way to promote weight loss or gain. The study depends on finding a way to determine the age of the fat cells that make up fatty tissues. The method is an extremely clever one; the researchers made use of the small amount of radioactive contamination absorbed by people who lived during the era of aboveground nuclear weapons testing, from 1955 until testing was banned in 1963.

Findings: Using their method, the authors of the study showed that by the time we end adolescence, our number of adipocytes has been set. Heavy people begin adulthood with more fat cells, and lighter people with fewer, and the numbers won't change as we age or as we become more obese or leaner. The only thing that does change, if we gain or lose weight, is how plump with fat each cell becomes. Meanwhile, however, even though the total adipocyte number remains constant, the cells themselves don't just sit there getting bigger and smaller. Instead, they constantly turn over. Whether you are heavy or lean, losing weight or gaining it, the same rule applies—every year about 10 percent of your body's fat cells die, and they are replaced by the same number of new ones.

Conclusion: We have no idea yet what controls and regulates the one-for-one turnover rate of fat cells. But if we could find and readjust the control mechanism—for example, setting it to replace an annual loss of 10 percent of fat cells with only 8 percent of new cells—we might find a whole new approach to the treatment of obesity. This research is likely to lead us in that direction.

Watch Dr. Spiesel's new video segment from Slate V:

Eating chocolate while pregnant

Question: Consciously or not, most of us believe that if something tastes good, it surely must be harmful. But the law is not universally true. A little wine, it turns out, helps protect against heart disease. Drinking coffee, we know, is associated with a lower risk of type 2 diabetes. Can chocolate, too, find redemption?

New research: I am pleased, indeed, to report that a recent study of pregnant women shows that the ones who eat chocolate, especially dark chocolate, are at a lower risk for preeclampsia (which used to be called toxemia). In 3 percent to 8 percent of pregnancies, usually during the third trimester, the mother's blood pressure rises, and she begins spilling protein in her urine. This condition is one of the most serious complications of pregnancy, posing great risk to both mother and baby. The cause is obscure. In fact, several different causes—for example, damage to the placenta from the maternal immune system, an abnormality in the circulation of the placenta, or damage to cells that line the blood vessels—may all lead to the same preeclampsia outcome.

Findings: While women can be treated to slow the effect of preeclampsia on both mother and child, there are, as yet, no preventative treatments. This is why the results of the new study are so interesting. The researchers focused on about 1,700 women. They figured out how much chocolate the women ate by asking them and by measuring a chemical marker for chocolate in blood from the baby's umbilical cord. Low levels of the chemical marker were associated with a higher risk for preeclampsia, while a history of eating five or more servings of chocolate weekly in the last trimester was associated with a 40 percent lower rate of preeclampsia than in women who ate chocolate less than once a week. (The servings came from hot chocolate, cocoa, chocolate milk, dark-chocolate candy, cake, cookies, or ice cream.)

Conclusion: Just as there is no clear answer about the cause of preeclampsia, we don't know why chocolate might prevent it. Finding the answer to the second question might help clarify the first. And in any case, if future research confirms these good tidings about chocolate, we'll have found a simple, inexpensive, and tasty way to reduce a common and serious pregnancy danger.

Ibuprofen and Alzheimer's

Question: Do common anti-inflammatory medications like ibuprofen (Advil or Motrin) or naproxen (Aleve, Anaprox, Naprosyn) prevent or delay the onset of Alzheimer's? Initial studies were inconclusive because they weren't big enough or conducted over a long enough period of time. And clinical trials in which patients with established Alzheimer's took these medications have shown no benefit.

New research: Now, however, a six-year-long study of mostly male Veterans Affairs patients offers evidence that these medications help stave off the mental deterioration of Alzheimer's. Excluding people who had already been diagnosed with Alzheimer's, the researchers identified about 50,000 patients who developed it during the six-year period of the study. Each was matched with four veterans without Alzheimer's, of about the same age and receiving care at the same VA hospital. The researchers then compared how much of the anti-inflammatory medications the Alzheimer's patients took with those taken by the veterans without this illness.

Findings: The results were striking and unequivocal. Use of the medicine—especially ibuprofen—was strongly associated with a lower risk of Alzheimer's disease. The longer the patient took an anti-inflammatory, the lower the risk. Taking ibuprofen for five or more years cut the risk of Alzheimer's almost in half.

Caveat: Ibuprofen is a cheap, easily available, commonly taken medicine—so what's the downside? Plenty. Like all anti-inflammatory drugs, ibuprofen can intensely irritate the lining of the gastrointestinal tract, sometimes leading to severe and life-threatening GI bleeding. In addition, when ibuprofen is taken along with the daily baby aspirin often recommended to decrease the risk of heart attacks and strokes, it interferes with the beneficial effects of the aspirin, rendering it useless. In rare instances, drugs in the anti-inflammatory class cause significant kidney damage or even failure. In short, the same medication that might well help prevent Alzheimer's can increase the risk of disastrous gastrointestinal bleeding and of heart attacks, strokes, and kidney damage.

Conclusion: What to do? The answer is far from clear. We need more research comparing the risks of taking ibuprofen with its benefits. Given what we know at present, don't start taking this medication on your own without discussing it with your doctor. We are all tantalized by the possibility of a cheap, simple treatment to delay or prevent Alzheimer's. But this treatment has significant risks of its own.

Sydney Spiesel is a pediatrician in Woodbridge, Conn., and clinical professor of pediatrics at Yale University's School of Medicine.

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