The Relationship between Whole Grain Intake and Body Weight: Results of Meta-Analyses of Observational Studies and Randomized Controlled Trials

Caleigh M Sawicki,Katie Koecher,Nicola M Mckeown,Marjorie Bell,Heather Nelson Cortes,Orsolya M Palacios,Kara A Livingston,Kevin C Maki

doi:10.3390/nu11061245

Abstract

Results from some observational studies suggest that higher whole grain (WG) intake is associated with lower risk of weight gain. Ovid Medline was used to conduct a literature search for observational studies and randomized controlled trials (RCTs) assessing WG food intake and weight status in adults. A meta-regression analysis of cross-sectional data from 12 observational studies (136,834 subjects) and a meta-analysis of nine RCTs (973 subjects) was conducted; six prospective cohort publications were qualitatively reviewed. Cross-sectional data meta-regression results indicate a significant, inverse correlation between WG intake and body mass index (BMI): weighted slope, −0.0141 kg/m2 per g/day of WG intake (95% confidence interval (CI): −0.0207, −0.0077; r = −0.526, p = 0.0001). Prospective cohort results generally showed inverse associations between WG intake and weight change with typical follow-up periods of five to 20 years. RCT meta-analysis results show a nonsignificant pooled standardized effect size of −0.049 kg (95% CI −0.297, 0.199, p = 0.698) for mean difference in weight change (WG versus control interventions). Higher WG intake is significantly inversely associated with BMI in observational studies but not RCTs up to 16 weeks in length; RCTs with longer intervention periods are warranted.

Highlights

Whole grains (WG) are grains that contain the entire nut or seed kernel, including the endosperm, bran, and germ, from the plant from which they are produced [1,2]
A flow diagram summarizing the results of the literature search is shown in Figure 1 for observational studies and Figure 2 for randomized controlled trials (RCTs)
Nine studies were cross-sectional by design [23,24,33,34,35,36,38,39], and the remaining three were designed as prospective cohort studies but provided cross-sectional data at baseline [3,37,40] (Table S5)

Summary

Introduction

Whole grains (WG) are grains that contain the entire nut or seed kernel, including the endosperm, bran, and germ, from the plant from which they are produced [1,2]. 100% whole grain (e.g., WG rolled oats and WG brown rice) or foods that contain some proportion of a whole grain ingredient (e.g., whole grain bread containing whole wheat flour) [1]. WG foods or foods containing significant quantities of WGs tend to be higher in fiber and contain more of other essential nutrients, including iron, zinc, magnesium, selenium, and B vitamins, than refined grains [1]. Data from observational studies consistently indicate a relationship between WG intake and dietary fiber consumption. Nutrients 2019, 11, 1245 the United States and Europe shows that total dietary fiber intake is significantly associated with WG intake such that total fiber intake is generally 50–100% higher in the top versus the bottom quintile or quartile of whole WG intake [3,4]. WG intake has been associated with healthful eating patterns and lower risk for several morbidities such as cardiovascular disease, diabetes, and obesity [1,5]

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