Substituting whole grains for refined grains in a 6-wk randomized trial favorably affects energy-balance metrics in healthy men and postmenopausal women1-3

J. Philip Karl, Mohsen Meydani, Junaidah B. Barnett, Sally M. Vanegas, Barry Goldin, Anne Kane, Helen Rasmussen, Edward Saltzman, Pajau Vangay, Dan Knights, C. Y. Oliver Chen, Sai Krupa Das, Satya S. Jonnalagadda, Simin N. Meydani, Susan B. Roberts

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Background: The effect of whole grains on the regulation of energy balance remains controversial. Objective: We aimed to determine the effects of substituting whole grains for refined grains, independent of body weight changes, on energy-metabolism metrics and glycemic control. Design: The study was a randomized, controlled, parallel-arm controlled-feeding trial that was conducted in 81 men and postmenopausal women [49 men and 32 women; age range: 40-65 y; body mass index (in kg/m2):,35.0]. After a 2-wk run-in period, participants were randomly assigned to consume 1 of 2 weight-maintenance diets for 6 wk. Diets differed in whole-grain and fiber contents [mean ± SDs: whole grain-rich diet: 207 ± 39 g whole grains plus 40 ± 5 g dietary fiber/d; refined grain-based diet: 0 g whole grains plus 21 ± 3 g dietary fiber/d] but were otherwise similar. Energy metabolism and body-composition metrics, appetite, markers of glycemic control, and gut microbiota were measured at 2 and 8 wk. Results: By design, body weight was maintained in both groups. Plasma alkylresorcinols, which are biomarkers of whole-grain intake, increased in the whole grain-rich diet group (WG) but not in the refined grain-based diet group (RG) (P-diet-by-time interaction, 0.0001). Beta ± SE changes (DWG compared with DRG) in the resting metabolic rate (RMR) (43 ± 25 kcal/d; P = 0.04), stool weight (76 ± 12 g/d; P < 0.0001), and stool energy content (57 ± 17 kcal/d; P = 0.003), but not in stool energy density, were higher in the WG. When combined, the favorable energetic effects in the WG translated into a 92-kcal/d (95% CI: 28, 156-kcal/d) higher net daily energy loss compared with that of the RG (P = 0.005). Prospective consumption (P = 0.07) and glycemia after an oral-glucose-tolerance test (P = 0.10) trended toward being lower in the WG than in the RG. When nonadherent participants were excluded, between-group differences in stool energy content and glucose tolerance increased, and between-group differences in the RMR and prospective consumption were not statistically significant. Conclusion: These findings suggest positive effects of whole grains on the RMR and stool energy excretion that favorably influence energy balance and may help explain epidemiologic associations between whole-grain consumption and reduced body weight and adiposity.

Original languageEnglish (US)
Pages (from-to)589-599
Number of pages11
JournalAmerican Journal of Clinical Nutrition
Volume105
Issue number3
DOIs
StatePublished - Mar 1 2017

Bibliographical note

Funding Information:
SMV was supported by a Stanley N Gershoff scholarship from the Tufts University Friedman School of Nutrition Science and Policy; a National Research Service Award for the National Institute of Diabetes and Digestive and Kidney Diseases T32 Research Training Program in Nutrition and Chronic Disease (grant 2T32DK062032-21)

Publisher Copyright:
© 2017 American Society for Nutrition.

Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.

Keywords

  • Body fat
  • Body weight
  • Continuous glucose monitoring
  • Energy metabolism
  • Fiber
  • Glucose tolerance
  • Glycemia
  • Hunger
  • Resting metabolic rate
  • Thermogenesis

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