diet

Fat vaccine works in rats

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(This article was #98 in Discover Magazine’s top 100 stories of 2006.)

In August, immunologist Kim Janda of the Scripps Research Institute grabbed headlines with reports of a vaccine against obesity. The vaccine triggers an immune response that targets ghrelin, a hormone naturally made in the gut and transported to the brain; ghrelin spikes with hunger and is thought to stimulate the storage of body fat.

In the study, rats that received the vaccine ate the same amount of food as the control group, but they gained less weight and had 20 percent less body fat. “I expected them to eat less, but it appears that what we saw was a result of metabolism,” Janda says. “Losing weight, losing fat—can’t ask for anything more than that!”

Now the reality check: The researchers followed the rats for only one week after the animals received their last booster shots. Long-term results could be very different. Michael Schwartz, professor of medicine at the University of Washington at Seattle, warns that the weight loss could prompt the body to compensate by making more of other weight-related hormones. Meanwhile, neuroscientist William Colmers of the University of Alberta worries about the wisdom of vaccinating the body against one of its own molecules. “It’s an intriguing idea, but it worries me considerably,” he says. “I sure as hell wouldn’t take it, no matter how fat I was.”

Low-fat diet a bust?

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(This article was #53 in Discover Magazine’s top 100 stories of 2006.)

The largest-ever experimental study examining whether a low-fat diet can prevent cancer and heart disease brought discouraging results. After following 48,835 postmenopausal women for eight years, scientists concluded that cutting fat from the diet doesn’t significantly reduce the incidence of breast or colorectal cancer, heart disease, or stroke. Results of the $415 million trial, part of the National Institutes of Health’s Women’s Health Initiative, were reported in three papers in the Journal of the American Medical Association.

Revised ideas about the role of fat in disease could help explain the murky data, notes Michael Thun, who heads epidemiological research for the American Cancer Society. For example, women in the study cut their total fat intake rather than specifically targeting saturated fats and trans fats, which are now known to contribute to heart disease risk. Cancer researchers are also starting to focus more on risks from obesity. “The evidence base has become very strong that it’s being fat rather than eating fat that’s associated with risk,” Thun says.

He and others plan to follow the women for an additional five years for more information. Meanwhile, the best advice from experts is to eat less saturated and trans fats and more fruits and vegetables.