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

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.

SUBMITTER: Maki KC

PROVIDER: S-EPMC6627338 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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

Maki Kevin C KC Palacios Orsolya M OM Koecher Katie K Sawicki Caleigh M CM Livingston Kara A KA Bell Marjorie M Nelson Cortes Heather H McKeown Nicola M NM

Nutrients 20190531 6

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 publication ...[more]

PMID: 31159235

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Project description:Within epidemiological and intervention studies, whole grain consumption has generally shown positive associations with reductions in markers of overweight and obesity. However, studies use varied methods of determining whole grain intake, including different definitions of a whole grain food, which may explain varied results. This systematic review aimed to identify how different methods of reporting and calculating whole grain intake, including whole grain food definitions, affect reported associations between whole grain intake and body weight measures in adults. Systematic searching of PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Central Register for Controlled Trials (CENTRAL), and MEDLINE (all years to 11 June, 2020) identified eligible studies. Cohort and cross-sectional studies assessing whole grain intake and body weight measures in adults were included. Studies that did not specify methods used to calculate whole grain intake were excluded. Twenty-one cross-sectional studies (from 24 articles) and 9 prospective cohort studies (from 7 articles) were included in the review. Many cross-sectional studies showed whole grain intake was, to some degree, significantly associated with body weight measures, whereas associations varied greatly among cohort studies. Studies calculating whole grain intake using total grams of intake, USDA databases, or ≥25% whole grain in combination with listing specific foods, showed consistent beneficial effects of increasing whole grain intake on body weight. Studies with general lists of foods included as "whole grain foods" or lower cut-offs for whole grain content were inconsistent. The majority of studies reported whole grain intake as servings/day or grams whole grain/day. This review suggests that an association between whole grain and body weight measures remains likely, although precise associations are difficult to determine due to heterogeneity in methodologies and an inability to formally compare studies. Moving forward, application of a standardized methodology to calculate whole grain intake is essential.

Project description:OBJECTIVE:To examine the associations between the intake of total and individual whole grain foods and the risk of type 2 diabetes. DESIGN:Prospective cohort studies. SETTING:Nurses' Health Study (1984-2014), Nurses' Health Study II (1991-2017), and Health Professionals Follow-Up Study (1986-2016), United States. PARTICIPANTS:158 259 women and 36 525 men who did not have type 2 diabetes, cardiovascular disease, or cancer at baseline. MAIN OUTCOME MEASURES:Self-reports of incident type 2 diabetes by participants identified through follow-up questionnaires and confirmed by a validated supplementary questionnaire. RESULTS:During 4 618 796 person years of follow-up, 18 629 participants with type 2 diabetes were identified. Total whole grain consumption was categorized into five equal groups of servings a day for the three cohorts. After adjusting for lifestyle and dietary risk factors for diabetes, participants in the highest category for total whole grain consumption had a 29% (95% confidence interval 26% to 33%) lower rate of type 2 diabetes compared with those in the lowest category. For individual whole grain foods, pooled hazard ratios (95% confidence intervals) for type 2 diabetes in participants consuming one or more servings a day compared with those consuming less than one serving a month were 0.81 (0.77 to 0.86) for whole grain cold breakfast cereal, 0.79 (0.75 to 0.83) for dark bread, and 1.08 (1.00 to 1.17) for popcorn. For other individual whole grains with lower average intake levels, comparing consumption of two or more servings a week with less than one serving a month, the pooled hazard ratios (95% confidence intervals) were 0.79 (0.75 to 0.83) for oatmeal, 0.88 (0.82 to 0.94) for brown rice, 0.85 (0.80 to 0.90) for added bran, and 0.88 (0.78 to 0.98) for wheat germ. Spline regression showed a non-linear dose-response association between total whole grain intake and the risk of type 2 diabetes where the rate reduction slightly plateaued at more than two servings a day (P<0.001 for curvature). For whole grain cold breakfast cereal and dark bread, the rate reduction plateaued at about 0.5 servings a day. For consumption of popcorn, a J shaped association was found where the rate of type 2 diabetes was not significantly raised until consumption exceeded about one serving a day. The association between higher total whole grain intake and lower risk of type 2 diabetes was stronger in individuals who were lean than in those who were overweight or obese (P=0.003 for interaction), and the associations did not vary significantly across levels of physical activity, family history of diabetes, or smoking status. CONCLUSION:Higher consumption of total whole grains and several commonly eaten whole grain foods, including whole grain breakfast cereal, oatmeal, dark bread, brown rice, added bran, and wheat germ, was significantly associated with a lower risk of type 2 diabetes. These findings provide further support for the current recommendations of increasing whole grain consumption as part of a healthy diet for the prevention of type 2 diabetes.

Project description:Background/objectivesPhysiological evidence indicates that high-protein diets reduce caloric intake and increase thermogenic response, which may prevent weight gain and regain after weight loss. Clinical trials have shown such effects, whereas observational cohort studies suggest an association between greater protein intake and weight gain. In both types of studies the results are based on average weight changes, and show considerable diversity in both directions. This study investigates whether the discrepancy in the evidence could be due to recruitment of overweight and obese individuals into clinical trials.Subjects/methodsData were available from the European Diet, Obesity and Genes (DiOGenes) post-weight-loss weight-maintenance trial and the Danish Diet, Cancer and Health (DCH) cohort. Participants of the DCH cohort were matched with participants from the DiOGenes trial on gender, diet, and body characteristics. Different subsets of the DCH-participants, comparable with the trial participants, were analyzed for weight maintenance according to the randomization status (high or low protein) of the matched trial participants.ResultsTrial participants were generally heavier, had larger waist circumference and larger fat mass than the participants in the entire DCH cohort. A better weight maintenance in the high-protein group compared to the low protein group was observed in the subgroups of the DCH cohort matching body characteristics of the trial participants.ConclusionThis modified observational study, minimized the differences between the RCT and observational data with regard to dietary intake, participant characteristics and statistical analysis. Compared with low protein diet the high protein diet was associated with better weight maintenance when individuals with greater body mass index and waist circumference were analyzed. Selecting subsets of large-scale observational cohort studies with similar characteristics as participants in clinical trials may reconcile the otherwise conflicting results.

Project description:The purpose of this study was (1) to describe intakes of total grain and whole grain in the United States over the past 12 years and major dietary sources, and (2) to determine the relationship between whole grain intake and adiposity measures for children and adults.Cross-sectional dietary data from the continuous National Health and Nutrition Examination Survey 2001-12 (6 2-year cycles) for children 6-18 years (n = 15,280) and adults 19+ years (n = 29,683) were linked to the My Pyramid and Food Patterns Equivalents Databases to assess daily intake of total grain and whole grain. These populations were classified into groups based on average whole grain intake: 0 ounce equivalents (oz eq)/day, > 0 and <1 oz eq/day, and ≥1 oz eq/day. Within these classifications, body mass index, waist circumference, and percent overweight/obese were identified. Regression and logistic regression analyses were used to assess associations between these dependent variables and whole grain intake.Adults consumed a mean 0.72 whole grain oz eq/day in 2001-02 and 0.97 oz eq/day in 2011-12 and children consumed a mean 0.56 whole grain oz eq/day in 2001-02 and 0.74 oz eq/day in 2011-12. While over 70 % of children and 60 % of adults met daily intake recommendations for total grain, less than 1.0 and 8.0 % percent of children and adults, respectively, met whole grain recommendations in 2011-12. Adults and children who consumed whole grain had significantly better intakes of nutrients and dietary fiber compared to non-consumers. From 2001 to 2012, grain mixed dishes and yeast breads were the leading sources of total grain, while yeast breads and ready to eat cereals were the leading sources of whole grain for both children and adults. Multiple regression analysis showed a significant, inverse relationship between body mass index and waist circumference with respect to whole grain intake after adjustment for covariates in both children and adults (p < 0.05). Similarly, logistic regression analysis showed a significant inverse relationship between percent overweight/obese and whole grain intake (p < 0.05).Although most children and adults meet daily intake goals for grain foods overall, whole grain as a portion of total grain intake continues to be consumed at levels well below recommendations. The data from the current study suggest that greater whole grain consumption is associated with better intakes of nutrients and healthier body weight in children and adults. Continued efforts to promote increased intake of whole grain foods are warranted.

Project description:Findings on the effect of whole-grain consumption on inflammatory biomarkers are conflicting. This study aimed to summarize available studies on the effects of whole-grain consumption on inflammatory biomarkers in adults. Online databases including PubMed, Scopus, ISI Web of Science, and Google Scholar were searched for relevant studies published up to January 2018, using relevant keywords. We included randomized controlled trials (RCTs) investigating the effect of whole-grain foods or diets high in whole-grain foods on markers of inflammation. Studies were selected if they had a control diet low in whole grains or diets without whole grains, whether calorie restricted or not. We did not include studies that examined the effect of individual grain components, including bran or germ, or fiber-based diets. Overall, 14 RCTs, with 1238 individuals aged ≥18 y, were included. Pooling 13 effect sizes from 11 RCTs on serum C-reactive protein (CRP) concentrations, we found no significant effect of whole-grain consumption on serum CRP concentrations [weighted mean difference (WMD): -0.29 mg/L; 95% CI: -1.10, 0.52 mg/L]. However, the beneficial effects of whole-grain intake on serum CRP concentrations were observed in studies in individuals with elevated serum concentrations of CRP and studies with isocaloric diets. Combining 11 effect sizes from 10 RCTs, we found no significant effect of whole-grain consumption on serum IL-6 concentrations (WMD: -0.08 pg/mL; 95% CI: -0.27, 0.11 pg/mL). Nevertheless, we observed a significant effect of whole-grain consumption on serum IL-6 concentrations in studies in unhealthy individuals. A nonsignificant effect of whole-grain intake on circulating serum TNF-α concentrations was also seen when we summarized effect sizes from 7 RCTs (WMD: -0.06 pg/mL; 95% CI: -0.25, 0.14 pg/mL). Such a nonsignificant effect was observed for serum concentrations of plasminogen activator inhibitor-1 (PAI-1) (WMD: -3.59; 95% CI: -1.25, 8.44 kU/L). Unlike observational studies, we found no significant effect of whole-grain consumption on serum concentrations of inflammatory cytokines, including serum concentrations of CRP, IL-6, TNF-α, and PAI-1. However, beneficial effects of whole grains were found in some subgroups. Given the high between-study heterogeneity, deriving firm conclusions is difficult.

Dataset Information

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

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

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