Nutritional quality of calorie restricted diets in the CALERIE™ 1 trial

Abstract

Objectives: The aim was to determine the nutritional adequacy of calorie restricted (CR) diets during CR interventions up to 12 months.

Methods: The Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE™) phase 1 trial consisted of 3 single-site studies to test the feasibility and effectiveness of CR in adults without obesity. After baseline assessments, participants who were randomized to a CR intervention received education and training from registered dietitians on how to follow a healthful CR diet. Food diaries were completed at baseline and during the CR interventions (~6, 9, and 12 months) when participants were self-selecting CR diets. Diaries were analyzed for energy, macronutrients, fiber, 11 vitamins, and 9 minerals. Nutritional adequacy was defined by sex- and age-specific Estimated Average Requirement (EAR) or Adequate Intake (AI) criteria for each nutrient. Diet quality was evaluated using the PANDiet diet quality index.

Results: Eighty-eight CR participants (67% women, age 40 ± 9 y, BMI 27.7 ± 1.5 kg/m²) were included in the analysis. Dietary intake of fiber and most vitamins and minerals increased during CR. More than 90% of participants achieved 100% of EAR or AI during CR for 2 of 4 macronutrients (carbohydrate and protein), 6 of 11 vitamins (A, B1, B2, B3, B6, B12), and 6 of 9 minerals assessed (copper, iron, phosphorus, selenium, sodium, zinc). Nutrients for which <90% of participants achieved adequacy included fiber, omega-3 fatty acids, vitamins B5, B9, C, E, and K, and the minerals calcium, magnesium, and potassium. The PANDiet diet quality index improved from 72.9 ± 6.0% at baseline to 75.7 ± 5.2% during CR (p < 0.0001).

Conclusion: Long-term, calorie-restricted diets were nutritionally equal or superior to baseline ad libitum diets among adults without obesity. Our results support modest calorie restriction as a safe strategy to promote healthy aging without compromising nutritional adequacy or diet quality.

Keywords: Calorie restriction; Diet quality; Nutritional adequacy; PANDiet.

Fig. 1.

CALERIE 1 trial eligibility criteria and participant flow by site. CR (calorie restriction), EX (exercise), LCD (low calorie diet). Shaded boxes reflect study groups that were not included in the present analysis.

Fig. 2.

Equation to calculate the probabilities of adequate intake for individual nutrients. Image from Verger et al. (2012).

Fig. 3.

Proportion of CR participants across all sites who achieved 100% of Estimated Average Requirement (EAR) or adequate intake (AI) for vitamins (top panel) and selected minerals and macronutrients (bottom panel) at baseline (BL, solid bars) and during calorie restriction (CR, striped bars). Data labels represent the % of participants.

Fig. 4.

PANDiet diet quality index at baseline and during calorie restriction (CR) for all participants combined and by site. Data labels within each boxplot represent the median values; the circles outside represent outliers.