Q: I understand that a magazine reported that a lot of the olive oil from Italy is adulterated with lesser oils and described ongoing fraud in the olive oil business. Do you have any information about this?

A: I have read the article you mention, which was published in the Aug. 13, 2007, issue of The New Yorker. Titled "Slippery Business," it was written by correspondent Tom Mueller. It reports that fraud remains a major problem in the international olive oil business and that adulteration with inferior oils (hazelnut and seed oils) is especially common in Italy, the world's leading importer, consumer and exporter of olive oil. The article notes that for the past 10 years, Spain has actually produced more olive oil than Italy, but much of the Spanish oil is shipped to Italy and then bottled and sold, legally, as Italian olive oil.

While chemical tests can identify some adulterated oils, they can't detect the most sophisticated scams, The New Yorker reported. Even the stringent taste tests established by the International Olive Oil Council to determine which oils qualify as "extra virgin" have their limitations — in Italy producers often successfully appeal a negative verdict by arguing that samples were incorrectly collected or stored or by resubmitting their samples to a friendlier panel.

Mueller did detail some of the cases of olive oil fraud investigated in Italy over the years — including one involving products adulterated with seed and hazelnut oil that were sold to some of the largest Italian producers, who then resold it to consumers worldwide as pure olive oil. In 1997 and 1998, olive oil was considered the most adulterated agricultural product in the European Union, so much so that the EU's anti-fraud office established an olive oil task force. One investigator told Mueller that profits from this criminal enterprise were "comparable to cocaine trafficking with none of the risks."

Cracking down on this problem is far from easy. Mueller reported that in Italy, officials who are responsible for detecting adulterated oil can, in theory, be held personally liable for their actions — thus, if a big sale of oil was blocked and charges of adulteration prove wrong, the officials who investigated could have to pay out of their own pockets for the olive oil company's losses! And, not surprising, many big producers have a great deal of political influence and are essentially immune to investigation, the article said.

This is an eye-opening and discouraging report on the business of olive oil. While it is clear that efforts are being made to solve the problems of the past, it's not at all clear that these efforts have a chance of succeeding in the present. I suggest that you buy small bottles from a reputable company or source. Look for the yellow-green color and deep olive flavor that indicate high-quality products. Certification as organic also can be a sign of quality. If you can find imported oils with certification by the International Olive Oil Council on the label, go for them. (The California Olive Oil Council certifies purity of oil produced in California.)

Q: What's this I hear about a virus causing obesity? If this is so, does it mean that there could be a vaccine to stop obesity or some way to treat it other than dieting?

A: If you're overweight and trying to lose a few pounds, I wouldn't give up on improving your habits of eating and exercise. But yes, new research does suggest that a virus may play a role in the development of obesity in some people. Here's the story:

Researchers from Louisiana State University's Pennington Biomedical Research Center have reported evidence suggesting that infection with human adenovirus-36 (Ad-36), a bug that causes common respiratory and eye infections, may actually cause fat levels to increase in human cells.

The findings were reported at the 234th national meeting of the American Chemical Society in Boston in August 2007. Investigators stressed that not everyone infected with Ad-36 will gain weight and that the virus is not the only cause of obesity. But an epidemiological study they conducted showed that 30 percent of obese people participating were infected with the virus, compared with only 11 percent of the lean people in the study. More recently, the Louisiana team took adult stem cells in fatty tissue from a cross section of people who had had liposuction. They then exposed half the stem cells to the virus (the other half was not exposed). After growing for about a week in tissue culture, the virus-infected cells turned into fat cells, while the noninfected cells didn't. The researchers also identified a gene in the virus that appears to be responsible for the change.

These findings eventually could lead to a vaccine or perhaps to an anti-viral drug that could inhibit the obesity virus. But that's a very long way off, and there are still many unanswered questions. We don't yet know how long the virus remains in the body or how long its fat-promoting effect lasts. Nor do we know exactly how the virus leads to obesity. The researchers are now trying to identify the factors that predispose some people infected with the virus to become obese while others don't.

Bear in mind that no one claims that a virus is solely responsible for obesity in humans. Genetic predisposition plays a role, certainly, but based on what we know now, lifestyle choices appear the most important, and those are under your control.

Readers can ask Dr. Weil a question by going to his Web site, www.drweil.com, and clicking "Ask Dr. Weil" and then "Ask Your Question." If your question is selected, look for Weil's response in an upcoming Q&A article.