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Am J Clin Nutr. 2017 Mar;105(3):589-599. doi: 10.3945/ajcn.116.139683. Epub 2017 Feb 8.

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

Author information

1
Jean Mayer USDA Human Nutrition Research Center on Aging and.
2
School of Medicine, Tufts University, Boston, MA.
3
Biomedical Informatics and Computational Biology and.
4
Department of Computer Science and Engineering, University of Minnesota, Minneapolis, MN; and.
5
Bell Institute of Health and Nutrition, General Mills, Minneapolis, MN.
6
Jean Mayer USDA Human Nutrition Research Center on Aging and susan.roberts@tufts.edu.

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 (ΔWG compared with ΔRG) 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. This trial was registered at clinicaltrials.gov as NCT01902394.

KEYWORDS:

body fat; body weight; continuous glucose monitoring; energy metabolism; fiber; glucose tolerance; glycemia; hunger; resting metabolic rate; thermogenesis

PMID:
28179223
PMCID:
PMC5320410
DOI:
10.3945/ajcn.116.139683
[Indexed for MEDLINE]
Free PMC Article

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