Adult Weight Management

AWM: Eating Frequency and Patterns (2013)

Citation:

Bazzano LA, Song Y, Bubes V, Good CK, Manson JE, Liu S. Dietary intake of whole and refined grain breakfast cereals and weight gain in men. Obes Res. 2005, Nov; 13 (11): 1,952-1,960.

PubMed ID: 16339127
 
Study Design:
Longitudinal study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to examine the association between whole- and refined-grain breakfast cereal intakes and changes in weight over time.

Inclusion Criteria:

U.S. male physicians, 40 to 84 years of age in 1982, participating in the Physician's Health Study, who provided information on breakfast cereal intake.

Exclusion Criteria:

History of myocardial infarction, stroke, transient cerebral ischemia or cancer (except non-melanoma skin cancer).

Description of Study Protocol:
  • Recruitment: This paper was an analysis of subjects participating in the previously completed Physicians' Health Study. Information on participant recruitment is not provided in this paper.
  • Design: Prospective cohort study
  • Intervention: This paper presented observational data. In the Physicians' Health Study, participants were randomized to a low-dose aspirin and beta-carotene to examine the primary prevention of cardiovascular disease and cancer.

Statistical Analysis

  • Intakes of whole- and refined-grain breakfast cereals were considered as both continuous (servings per day) and categorical variables
  • Average change in BMI and weight gain were calculated using generalized linear regression model for two time intervals: Eight years from baseline and 13 years from baseline
  • Models were adjusted for age and baseline BMI as continuous variables and smoking, alcohol intake, physical activity, history of hypertension, history of high cholesterol and use of multi-vitamins as categorical variables
  • Cox proportional hazards models were used to calculate relative risks for unhealthy BMI and weight gain.
Data Collection Summary:

Timing of Measurements

  • At baseline, participants self-reported demographic, medical history and lifesyle variables
  • Follow-up questionnaires were administered every six months for the first year and annually thereafter
  • The semi-quantitative food frequency questionnaire (SFFQ) was only completed at baseline.

Dependent Variables

Self-reported weight and height (and calculated BMI), assessed through mailed questionnaires.

Independent Variables

Breakfast cereal consumption was assessed through two questions on a 61-item SFFQ

  • The first question queried frequency of "Cold Breakfast Cereal (one cup)"
  • The second question asked participants to specify brand and type of "cold breakfast cereal you usually eat?"
  • Whole grain cereals were defined as cereals with over 25% whole grain or bran content by weight.
Description of Actual Data Sample:
  • Initial N: The Physician Health Study consisted of 22,071 US male physicians
  • Attrition (Final N): After excluding those who had a history of diabetes, cancer or CVD at baseline and those who did not report weight, height and breakfast cereal intake at baseline, the final population for analyses included 17,881 men
  • Age: 40 to 84 years of age in 1982
  • Ethnicity: Not provided.

Other Relevant Demographics

  • At baseline, men who ate breakfast cereals more often tended to be older, tended to exercise and were less likely to be overweight, to smoke, to have a history of hypertension or to use multi-vitamin supplements than their counterparts with infrequent cereal intake
  • Men in the lowest category of whole grain breakfast cereal intake were significantly heavier than those in the highest category of whole grain intake (BMI, 24.8 vs. 24.1kg per m2; P<0.0001 for trend)
  • Men in the lowest category of refined grain breakfast cereal intake were also significantly heavier than those in the highest category of refined grain (BMI, 24.7 vs. 24.2kg per m2; P<0.0001 for trend)
  • Both or these findings were also true at the eight-year and 13-year follow-ups (P<0/0001 for trend).

Location

United States.

Summary of Results:

Adjusted Mean in Body Weight Gain (in kg) According to Intakes of Whole Grain, Refined Grain and Total Breakfast Cereals During an Eight- and 13-Year Follow-Up

  • Over the eight years follow-up period, men with a higher intake of breakfast cereals had significantly less weight gain (1.07±0.09kg, compared with 1.66±0.07kg; P<0.0001 for trend), regardless of grain type, age, smoking, baseline BMI, alcohol intake, physical activity, history of hypertension, history of high cholesterol or use of multi-vitamins
  • This trend was also found at the 13-year follow-up, where higher intake of total breakfast cereal was associated with lower weight gains, independent of age and other covariates
  • After 13 years, mean weight gain was significantly lower among participants consuming whole grain cereals at least one serving per day, compared with those who rarely or never consumed whole grain cereals (2.28±0.06kg, compared with 1.87±0.12kg; P=0.014 for trend), after adjustment for age
  • After adjusting for other covariates, the association did not meet the customary level of statistical significance.

Adjusted RRs (95% CI) for Attained BMI Over 25kg per m2, According to Intakes of Whole Grain, Refined Grain and Total Breakfast Cereals During an Eight- and 13-Year Follow-Up

Variables

Rarely or Never

≥1 Serving per Day*

P for Trend

8-Year Follow-Up; Whole Grain Breakfast Cereals

1.00

0.83 (0.71, 0.98)

0.06

8-Year Follow-Up; Refined Grain Breakfast Cereals

1.00

0.81 (0.64, 1.03)

0.03

8-Year Follow-Up; Total Breakfast Cereals

1.00

0.78 (0.67, 0.91)

0.001

13-Year Follow-Up; Whole Grain Breakfast Cereals

1.00

0.91 (0.79, 1.05)

0.13

13-Year Follow-Up ; Refined Grain Breakfast Cereals

1.00

0.81 (0.65, 1.01)

0.08

13-Year Follow-Up; Total Breakfast Cereals

1.00

0.88 (0.76, 1.00)

0.01

*Adjusted for age, smoking, baseline BMI, alcohol, physical activity, history of hypertension, history of high cholesterol and use of multi-vitamin.

Adjusted RRs (95% CI) for Attained Body Weight Gain >10 or >15kg According to Intakes of Whole Grain, Refined Grain and Total Breakfast Cereals During an Eight- and 13-Year Follow-Up

Variables

Rarely or Never

≥1 Serving per Day*

P for Trend

Whole grain breakfast cereals; >10 kg weight grain

1.00

0.78 (0.64, 0.96)

0.01

Whole Grain Breakfast Cereals; ≥15kg Weight Grain

1.00

0.82 (0.58, 1.16)

0.27

Refined Grain Breakfast Cereals; ≥10kg Weight Grain

1.00

0.77 (0.56, 1.06)

0.05

Refined Grain Breakfast Cereals; ≥15kg Weight Grain

1.00

0.69 (0.39, 1.22)

0.21

Total Grain Breakfast Cereals; ≥10kg Weight Grain

1.00

0.70 (0.58, 0.85)

0.0003

Total Grain Breakfast Cereals; ≥15kg Weight Grain

1.00

0.74 (0.54, 1.02)

0.08

* Adjusted for age, smoking, baseline BMI, alcohol, physical activity, history of hypertension, history of high cholesterol and use of multi-vitamin.

Author Conclusion:
  • In this 13-year prospective study, a higher intake of breakfast cereals was associated with lower BMI, lower risk of becoming overweight or obese and lower risk of major weight gain during the study follow-up periods. These associations did not differ by the type of grain (whole vs. refined) in breakfast cereals.
  • The definition used to characterize whole grains (cereals over 25% whole grain or bran content) may have led to misclassification that would bias results towards similar associations between whole and refined grains
  • The authors note that the total whole or refined grain was not examined in this study; only contributions by breakfast cereals. Additionally, changes in diet, over time, could confound the relationship between breakfast cereal intake and weight gain over time. The SFFQ hindered the ability to adjust for total energy intake and other dietary factors that may affect weight gain.
Funding Source:
Government: NHLBI
Reviewer Comments:
  • It is important to note that although weight was assessed at several intervals over the cohort study, dietary intake was only assessed at baseline, using an SFFQ
  • Another over-riding limitation relates to the generalizability of these findings (from a group of physicians) to the general population
  • Otherwise, the statistical methods are appropriate and the authors address the limitations imposed by use of an SFFQ (inability to capture total caloric intake and other dietary factors that may have affected weight gain).
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  3. Were study groups comparable? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  4. Was method of handling withdrawals described? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  5. Was blinding used to prevent introduction of bias? ???
5. Was blinding used to prevent introduction of bias? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) ???
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  7. Were outcomes clearly defined and the measurements valid and reliable? Yes
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.7. Were the measurements conducted consistently across groups? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes