Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy Phase 2 (CALERIE Phase 2) screening and recruitment: Methods and results

T. M. Stewart, M. Bhapkar, S. Das, K. Galan, C. K. Martin, L. McAdams, C. Pieper, L. Redman, S. Roberts, R. I. Stein, J. Rochon, D. A. Williamson

Research output: Contribution to journalArticle

34 Scopus citations


The Comprehensive Assessment of the Long-term Effects of Reducing Intake of Energy Phase 2 (CALERIE) study is a systematic investigation of sustained 25% calorie restriction (CR) in non-obese humans. CALERIE is a multicenter (3 clinical sites, one coordinating center), parallel group, randomized controlled trial. Participants were recruited, screened, and randomized to the CR or control group with a 2:1 allocation. Inclusion criteria included ages 21-50years for men and 21-47years for women, and a body mass index (BMI) of 22.0≤BMI<28.0kg/m2. Exclusion criteria included abnormal laboratory markers, significant medical conditions, psychiatric/behavioral problems, and an inability to adhere to the rigors of the evaluation/intervention schedule. A multi-stage screening process (telephone screen and 3 in-clinic visits) was applied to identify eligible participants. Recruitment was effective and enrollment targets were met on time. 10,856 individuals contacted the clinical sites, of whom 9787 (90%) failed one or more eligibility criteria. Of the 1069 volunteers who started the in-clinic screening, 831 (78%) were either ineligible or dropped. 238 volunteers were enrolled (i.e., initiated the baseline evaluations), 220 were randomized, and 218 started the assigned intervention (2% from the first screening step). This study offered lessons for future multi-center trials engaging non-disease populations. Recruitment strategies must be tailored to specific sites. A multi-disciplinary screening process should be applied to address medical, physical, and psychological/behavioral suitability of participants. Finally, a multi-step screening process with simple criteria first, followed by more elaborate procedures has the potential to reduce the use of study resources.

Original languageEnglish
Pages (from-to)10-20
Number of pages11
JournalContemporary Clinical Trials
Issue number1
StatePublished - Jan 1 2013


  • Aging
  • Caloric restriction
  • Consort information
  • Participant recruitment
  • Participant screening
  • Randomized controlled trial

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