One year of caloric restriction in humans: feasibility and effects on body composition and abdominal adipose tissue

Abstract

Background: Caloric restriction (CR) increases maximal life span in short-lived organisms, and its effects are being explored in nonhuman primates. The objectives of this study were to determine the feasibility of prolonged CR in nonobese adults and to compare the effects of CR- and exercise-induced weight loss on body composition and abdominal adiposity.

Methods: A randomized, controlled trial was conducted with 48 healthy, nonobese women and men, aged 57 +/- 1 (mean +/- standard error [SE]) years, with body mass index 27.3 +/- 0.3 kg/m2. Participants were randomly assigned to a 20% calorically-restricted diet (CR, n = 19), exercise designed to produce a similar energy deficit (EX, n = 19), or a healthy lifestyle control group (HL, n = 10) for 1 year. Assessments included weight, body composition by dual-energy x-ray absorptiometry, abdominal adipose tissue by magnetic resonance imaging, and energy intake by doubly labeled water.

Results: The average level of CR achieved by the CR group was 11.5 +/- 2.1%, and the EX group completed 59 +/- 6.7% of their prescribed exercise. Weight changes were greater (p <or=.0005) in the CR (-8.0 +/- 0.9 kg) and EX (-6.4 +/- 0.9) groups as compared to the HL group (-1.3 +/- 0.9 kg), corresponding to reductions of 10.7%, 8.4%, and 1.7% of baseline weights, respectively. Whole-body fat mass and visceral and subcutaneous abdominal adipose tissue decreased significantly (p <.005) and comparably in the CR and EX groups, but did not change in the HL group.

Conclusions: CR for 1 year was feasible, but the level of CR achieved was less than prescribed. CR and exercise were equally effective in reducing weight and adiposity.

Figures

Figure 1

Consort diagram depicting the flow of participants through the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) trial at Washington University School of Medicine.

Figure 2

Body weight changes throughout the 1-year interventions. Symbols represent mean values (black circles, caloric restriction [CR]; black triangles, exercise [EX]; open circles, healthy lifestyle [HL]) ± standard error.

Figure 3

Visceral (black bars) and subcutaneous (white bars) abdominal adipose tissue by magnetic resonance imaging (MRI) at baseline and after 1 year of intervention. CR, caloric restriction; EX, exercise; HL, healthy lifestyle. Final values were adjusted for baseline differences between groups. Values of p represent the change within group from baseline (BL) to 1 year. For comparison between groups, the following contrasts were significant: CR versus HL for visceral adipose tissue (p = .05), CR versus HL for subcutaneous adipose tissue (p = .02), and EX versus HL for visceral adipose tissue (p = .01).

Figure 4

Magnetic resonance images of the abdomen at baseline (BL) and after the 1 year of caloric restriction (CR) (A) and exercise (EX) (B) interventions. Single-slice images are shown, although analyses were based on multislice volume estimates. The CR participant is a 54-year-old woman whose body weight decreased 12 kg (19%); the EX participant is a 60-year-old man whose weight decreased 16 kg (14%).