Diet quality and nutritional adequacy during a 2-year calorie restriction intervention: the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy 2 trial

Background: Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE) was the first randomized controlled trial of calorie restriction (CR) on biomarkers of aging and cardiometabolic health in humans without obesity. Objectives: The aim of this secondary data analysis was to evaluate diet quality and nutritional adequacy during a 2-y CR intervention among healthy adults in the CALERIE trial. Methods: CALERIE 2 was a multisite trial of healthy adults randomly assigned to 2 y of 25% CR or an ad libitum (AL) control condition. CR participants received extensive dietary education and support. Food records at baseline (BL) and months 6, 12, 18, and 24 were analyzed using Nutrition Data System for Research. Diet quality was evaluated using the Probability of Adequate Nutrient Intake (PANDiet) diet quality index, Healthy Eating Index (HEI), and Dietary Inflammatory Index (DII). Nutritional adequacy was defined using sex- and age-specific Estimated Average Requirement or Adequate Intake criteria for each nutrient. Results: Two hundred eighteen participants began the trial and are included in the analyses [143 CR, 75 AL; 69.7% females, age 38.1 ± 7.2 y (mean ± SD), BL body mass index: 25.1 ± 1.7 kg/m²]. One hundred eighty-eight participants completed the trial (82% CR, 95% AL). Average CR achieved during the 2-y intervention was 11.9% ± 7.2%. Diet quality scores improved during CR according to all 3 metrics, both within group and when compared with AL (all P < 0.01): PANDiet [CR BL 76.27%, 95% confidence interval: 75.45%, 77.09%; CR 2 y average 77.38% (76.58%, 78.19%)], HEI: [BL 59.40 (57.62, 61.18); 2 y average 66.83 (65.11, 68.55)], and DII: [BL –0.28 (–0.58, 0.01); 2 y average –1.05 (–1.35, –0.74)]. Nutritional adequacy was not compromised during the CR intervention. Conclusions: Diet quality improved and nutritional adequacy was maintained during a 2-y moderate CR intervention designed to enhance healthspan and comprised comprehensive nutrition counseling among healthy adults without obesity. The study was registered at clinicaltrials.gov as NCT00427193 (https://clinicaltrials.gov/study/NCT00427193?term=NCT00427193&rank=1).