Study Background
Download "CALERIE at a Glance," an Overview of the Study Design with assessment schedules.
Download Overview and Introduction to CALERIE Slides.
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 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.
Summary of Findings
Effects of the CALERIE intervention on its primary and secondary outcomes, as well as several exploratory outcomes, are published in A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity. Additional CALERIE 2 publications are available via the search tool in Publications section of this website. The following provides a brief summary of key findings.
In CALERIE Phase 2, participants achieved 12% CR and sustained 10% weight loss over two years. In regards to CALERIE’s two primary outcomes, the intervention did not significantly affect core temperature and lowered RMR (adjusted for changes in body energy stores) only in the first year of the intervention. The intervention significantly affected both of the CALERIE secondary outcomes, producing diminutions in circulating levels of both T3 and TNF-ɑ. It also markedly lowered a variety of cardiometabolic risk factors.
Caloric restriction at levels achieved in CALERIE was safe and generally well tolerated (with the inherent limitations on conclusions from a trial of limited size). The CALERIE intervention produced a small diminution in bone mineral density, though not in excess of expected changes based on weight. CR at levels achieved in CALERIE Phase 2 had some positive effects and no negative effects on quality of life and psychological outcomes.
As described here, the CALERIE intervention did not significantly affect changes in circulating levels of platelet-derived growth factor AB, transforming growth factor beta, or insulin-like growth factor 1 (IGF-1), which has been proposed to mediate a variety of aging processes, but significantly increased circulating levels of IGF-1 binding protein. It produced small transient elevation on circulating cortisol.
Other analyses of CALERIE findings are in progress.
CALERIE Study Contact Information
Contact email for scientists desiring to become a network member and join research related to caloric restriction, or request help with statistical analyses of CALERIE data. Please note, we do not provide specific dietary or clinical advice about CR or other diet interventions.
Steering Committee
Clifford Rosen, MD, Committee Chair
Director, Clinical and Translational Research
Senior Scientist
Maine Medical Center Research Institute
Sai Krupa Das, PhD
Scientist, Professor
Jean Mayer, USDA, Human Nutrition Research Center on Aging
Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy
Tufts University
Boston, MA
Kim M. Huffman, MD, PhD
Professor
Division of Rheumatology & Immunology
Duke Molecular Physiology Institute
Duke University School of Medicine
300 N. Duke Street, 51-202
Durham, NC 27701
William E. Kraus, MD
Professor
Director of Clinical Translation, Duke Molecular Physiology Institute
Duke University School of Medicine
300 N. Duke Street, 51-201
Durham, NC 27701
Corby K. Martin, PhD
Professor
Pennington Biomedical Research Center
6400 Perkins Rd.
Baton Rouge LA 70808
Carl F. Pieper, DrPH
Professor
Duke Department of Biostatistics & Bioinformatics
0508 Busse Building
Durham, NC 27710
Susan B. Racette, PhD
Professor
Washington University School of Medicine
Leanne Redman, PhD
Professor
Reproductive Endocrinology and Women’s Health
Pennington Biomedical Research Center
6400 Perkins Rd.
Baton Rouge, LA 70808
James White, PhD
Associate Professor
Division of Hematology
Duke Molecular Physiology Institute
Duke University School of Medicine
300 N. Duke Street, 51-207
Durham, NC 27701
External Science Committee
Rozalyn M Anderson, PhD
Professor
Department of Medicine SMPH
University of Wisconsin-Madison
Daniel Belsky, PhD
Associate Professor
Department of Epidemiology & Butler Aging Center
Columbia University Mailman School of Public Health
National Institute on Aging
Chhanda Dutta, Ph.D.
Chief, Clinical Gerontology Branch
Division of Geriatrics and Clinical Gerontology
National Institute on Aging, NIH
Gateway Building, Suite 3W-200
7201 Wisconsin Ave
Bethesda, MD 20892