Balasubramanian, Priya, Porsha R. Howell, and Rozalyn M. Anderson. “Aging and Caloric Restriction Research: A Biological Perspective With Translational Potential.” EBioMedicine 21 (June 19, 2017): 37–44. https://doi.org/10.1016/j.ebiom.2017.06.015.

For primates, this is a good review:

Mattison, Julie A., Ricki J. Colman, T. Mark Beasley, David B. Allison, Joseph W. Kemnitz, George S. Roth, Donald K. Ingram, Richard Weindruch, Rafael de Cabo, and Rozalyn M. Anderson. “Caloric Restriction Improves Health and Survival of Rhesus Monkeys.” Nature Communications 8, no. 1 (January 17, 2017): 14063. https://doi.org/10.1038/ncomms14063.

Abstract: Caloric restriction (CR) without malnutrition extends lifespan and delays the onset of age-related disorders in most species but its impact in nonhuman primates has been controversial. In the late 1980s two parallel studies were initiated to determine the effect of CR in rhesus monkeys. The University of Wisconsin study reported a significant positive impact of CR on survival, but the National Institute on Aging study detected no significant survival effect. Here we present a direct comparison of longitudinal data from both studies including survival, bodyweight, food intake, fasting glucose levels and age-related morbidity. We describe differences in study design that could contribute to differences in outcomes, and we report species specificity in the impact of CR in terms of optimal onset and diet. Taken together these data confirm that health benefits of CR are conserved in monkeys and suggest that CR mechanisms are likely translatable to human health.

For human studies, here's a recent one:

Redman, Leanne M., Steven R. Smith, Jeffrey H. Burton, Corby K. Martin, Dora Il’yasova, and Eric Ravussin. “Metabolic Slowing and Reduced Oxidative Damage with Sustained Caloric Restriction Support the Rate of Living and Oxidative Damage Theories of Aging.” Cell Metabolism 27, no. 4 (April 3, 2018): 805-815.e4. https://doi.org/10.1016/j.cmet.2018.02.019.

"Findings from this 2-year CR trial in healthy, non-obese humans provide new evidence of persistent metabolic slowing accompanied by reduced oxidative stress, which supports the rate of living and oxidative damage theories of mammalian aging."

So we have to make the best of other evidence, like animal studies (rats have increased lifespan on restricted calories), observational studies, and biomarkers.

David A. Sinclair, Ph.D., A.O. is a Professor in the Department of Genetics and co-Director of the Paul F. Glenn Center for the Biology of Aging at Harvard Medical School. He is best known for his work on understanding why we age and how to slow its effects. He obtained his Ph.D. in Molecular Genetics at the University of New South Wales, Sydney in 1995. He worked as a postdoctoral researcher at M.I.T. with Dr. Leonard Guarente where he co discovered a cause of aging for yeast as well as the role of Sir2 in epigenetic changes driven by genome instability. In 1999 he was recruited to Harvard Medical School where he has been teaching aging biology and translational medicine for aging for the past 16 years. His research has been primarily focused on the sirtuins, protein-modifying enzymes that respond to changing NAD+ levels and to caloric restriction (CR) with associated interests in chromatin, energy metabolism, mitochondria, learning and memory, neurodegeneration, and cancer. The Sinclair lab was the first one to identify a role for NAD+ biosynthesis in regulation of lifespan and first showed that sirtuins are involved in CR in mammals. They first identified small molecules that activate SIRT1 such as resveratrol and studied how they improve metabolic function using a combination of genetic, enzymological, biophysical and pharmacological approaches. They recently showed that natural and synthetic activators require SIRT1 to mediate the in vivo effects in muscle and identified a structured activation domain. They demonstrated that miscommunication between the mitochondrial and nuclear genomes is a cause of age-related physiological decline and that relocalization of chromatin factors in response to DNA breaks may be a cause of aging.

Dr. Sinclair is co-founder of several biotechnology companies (Sirtris, Ovascience, Genocea, Cohbar, MetroBiotech, ArcBio, Liberty Biosecurity) and is on the boards of several others. He is also co-founder and co-chief editor of the journal Aging. His work is featured in five books, two documentary movies, 60 Minutes, Morgan Freeman’s “Through the Wormhole” and other media. He is an inventor on 35 patents and has received more than 25 awards and honors including the CSL Prize, The Australian Commonwealth Prize, Thompson Prize, Helen Hay Whitney Postdoctoral Award, Charles Hood Fellowship, Leukemia Society Fellowship, Ludwig Scholarship, Harvard-Armenise Fellowship, American Association for Aging Research Fellowship, Nathan Shock Award from the National Institutes of Health, Ellison Medical Foundation Junior and Senior Scholar Awards, Merck Prize, Genzyme Outstanding Achievement in Biomedical Science Award, Bio-Innovator Award, David Murdock-Dole Lectureship, Fisher Honorary Lectureship, Les Lazarus Lectureship, Australian Medical Research Medal, The Frontiers in Aging and Regeneration Award, Top 100 Australian Innovators, and TIME magazine’s list of the “100 most influential people in the world”.

https://genetics.med.harvard.edu/sinclair/people/sinclair.ph...