Caloric restriction (CR) has been shown in several—but not all—laboratory animal models to increase life span and to delay or slow the progression of a wide variety of aging changes and age-related pathologies. The CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy) clinical trial was the first study to focus specifically focus on the effects of sustained CR in humans. CALERIE demonstrated the feasibility of sustained human CR (for at least two years) and the favorable effects on predictors of longevity and cardiometabolic risk factors. No previous clinical study of non-obese individuals attained the degree of CR nor the resulting sustained weight loss that was achieved in CALERIE. Other noteworthy features of CALERIE are the substantial size of the trial, the comprehensive physiologic, psychologic, Quality of Life (QOL) and cognitive assessments conducted, as well as the extensive collection of biological samples which include serum, plasma, urine, and biopsies from skeletal muscle (vastus lateralis) and adipose tissue (subcutaneous abdominal). Detailed documentation about measures available in the CALERIE database and stored specimens available for future studies is available in the Database Documentation and Biorepository sections of this website.
These features, combined with the careful attention to detail in the collection of data, make the publicly available CALERIE data sets and biospecimens a unique and invaluable research resource for the investigation of innumerable hypotheses about the biological mechanisms underlying the effects of CR on human aging biology and for translational research to develop strategies for promoting health span.
The CALERIE trials were conducted in two phases. Phase 1 of CALERIE consisted of three single-site pilot randomized controlled studies testing differing degrees of caloric restriction (20%, 25%, and 30%) in a range of age groups with BMIs between 25.0 and 30 (i.e., overweight status) for six months to one year. Data from CALERIE Phase 1 studies informed design of the two-year CR Phase 2 study. Papers describing the Phase 1 studies’ design and results are available via the Publications search tool.