A low-calorie diet not only checks weight but also boosts immunity, according to a recent study.

The study led by Simin Nikbin Meydani, director of the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University in Boston, demonstrates the interaction between calorie restriction and immune markers among humans.

As people age, their immune response generally declines. Calorie restriction has been shown to boost these immune responses in animal models.

The study is part of the "Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy" trial conducted at the HNRCA.

In the study, 46 overweight (but not obese) men and women aged 20 to 40 years were required to consume either a 30 percent or 10 percent calorie-restricted diet for six months.

Prior to being randomly assigned to one of the two groups, each volunteer participated in an initial six-week period during which measures of all baseline study outcomes were obtained. All food was provided to participants.

For the study, the researchers looked at specific biologic markers -- a skin test, called DTH (delayed-type hypersensitivity), a measure of immune response at the whole body level.

The researchers also examined effects of calorie restriction on function of T-cells -- a major type of white blood (immune) cell -- and other factors on the volunteer's immune system, says a Tufts University release.

These results show for the first time that short-term calorie restriction for six months in humans improves the function of T-cells.