May 26, 2010

Lose Weight and Boost Immunity

Even people with moderate reduction in calorie intake saw their body’s defense system get stronger

By Julie Flaherty

Both groups, as expected, lost pounds, but they also boosted their immune response by 30 to 50 percent, according to the study published in the Journal of Gerontology. Photo: iStock

Losing extra pounds by cutting calories may benefit your immune system as well as your waistline, Tufts researchers have found, and could be a sign that low-cal eating leads to longer life.

For the study, 46 overweight (but not obese) men and women, ages 20 to 42, were provided with a nutritionally complete but calorie-restricted diet for six months. They were supplied with food that cut their usual caloric intake by either 10 percent or 30 percent.

Simin Nikbin Meydani, director of the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts, and colleagues judged the participants’ immune strength by looking at their T-cells, a kind of white blood cell that helps the body fight tumors, viruses and bacterial infection. At the beginning and end of the study, participants were given a skin test that primarily measures how well T-cells react to antigens. Researchers also drew blood to assess T-cell proliferation.

Both groups, as expected, lost pounds, but they also boosted their immune response by 30 to 50 percent. The group that cut a higher percentage of calories showed the biggest changes, but even those who lost a few pounds saw improvements.

“That’s good, because it means you don’t have to do heroics before you can see a benefit,” says Meydani, who also heads the HNRCA’s nutritional immunology lab.

The finding is intriguing, Meydani says, because if restricting calories boosts immunity, it may be an indication that the aging process is slowed down in people who carefully control their diets. A weakened immune response is a well-known hallmark of aging, with our T-cells in particular becoming less effective as we grow older.

Similar immunity benefits have been found in animals that were fed austere diets to keep their body weight in check. Those animals went on to live much longer lives than their eat-at-will peers.

“It bodes well in saying that what we observe in animals is reproducible in humans,” says Meydani, a professor at the Friedman and Sackler Schools.

An important next step would be to see if people on nutritious, low-calorie diets are actually better protected from infectious diseases. “If we see increased resistance to infection, that’s very good evidence that we might be able to extend life,” Meydani says. It could be one step in proving that humans, like rats and mice, could also up their life span if they are willing to live lean.

Julie Flaherty can be reached at

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