Research conducted at the Washington University School of Medicine, St. Louis, has found that eating a low-calorie diet, which is also nutritionally well balanced, reduces the levels of a thyroid hormone called triiodothyronine (T3). The triiodothyronine (T3) controls the body's energy balance and cellular metabolism. The study also revealed that calorie restriction decreases the circulating concentration of a inflammatory molecule tumor necrosis factor alpha (TNF). The combination of lower T3 levels and reduced inflammation may slow the aging process by reducing the body's metabolic rate as well as oxidative damage to cells and tissues. Clinical trials on rats has revealed that both calorie restriction and exercise, help prevent chronic diseases like obesity, diabetes, cardiovascular disease and few types of cancer. The animal studies suggest that reducing caloric intake is required to slow down aging. The study has led to the conclusion that exercise helps prevent health problems such as obesity, diabetes and cardiovascular disease, only calorie restriction helps in arresting signs of aging.