McCay was professor of
animal husbandry at
Cornell University from 1927 to 1963. His main interest was the influence of nutrition on aging. He is best known for his work in proving that
caloric restriction increases the life span of rats, which is seen as seminal in triggering further research and experiments in the field of nutrition and longevity. Scientists are still trying to understand the connection between caloric restriction and longevity. Following his discovery between a low calorie diet and longevity, McCay played a prominent role in the development of nutritionally-sound rations during
World War II, and the creation of
Cornell Bread, designed for high
protein and
vitamin content, similar to the meal fed to mice in longevity experiments. Another of McCay's important contributions was the first work in
heterochronic parabiosis: the joining of the circulatory systems of a young and an old animal, which leads to rejuvenating effects on the tissues of the old animal and degenerative changes in the young's, thus demonstrating the role of systemic factors in aging. Limited work with this paradigm by others continued into the early 1970s before languishing, until it was finally taken up again by researchers at
Stanford University and the
University of California at Berkeley in the mid-2000s. His further research centered on canine nutrition, and
fluoride and its use in water treatment. ==Selected publications==