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Adult Weight Management

AWM: Nutrition Education (2006)

Citation:

Kral TVE, Roe LS, Rolls BJ.  Does nutrition information about the energy density of meals affect food intake in normal-weight women?  Appetite 2002; 39(2): 137-145.

PubMed ID: 12354682
 
Study Design:
Non-Randomized Controlled Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To investigate whether the energy density of foods affected energy intake when subjects were informed about the energy density of their meals.
Inclusion Criteria:
Healthy, normal-weight women, aged 18 - 45, not athletes in training, not pregnant or lactating, non-smokers, free from food allergies, not dieting, regularly eating 3 meals/day, BMI 20 - 25, weight stable for past 6 months.  Only women scoring < 20 on Eating Attitudes Test and < 40 on Zung Self-Rating Depression Scale qualified for participation.
Exclusion Criteria:
Excluded if not included above.
Description of Study Protocol:

Recruitment

Recruited by advertisement in campus newspaper.

Design

Nonrandomized clinical trial, between-subjects design.

Blinding used (if applicable)

Not used.

Intervention (if applicable)

Subjects ate breakfast, lunch and dinner in the lab on 3 separate days, with entree varying in energy density.  Subjects assigned to groups of receiving a nutrition label with each meal showing energy density, or not.

Statistical Analysis

Fisher's procedure was used for post hoc comparisons for significant effects.  Food intake, energy intake, fiber intake and VAS ratings were analyzed using the mixed linear model procedure with repeated measures.  Subject group and condition of energy density were entered as fixed factors in the model and subjects treated as a random factor.  Subject characteristics such as age, height, weight, BMI, dietary restraint, disinhibition, and hunger, as well as scores on Eating Attitudes Test and Zung Self-Rating Depression Scale were tested as covariates with daily food intake using ANCOVA.  Linear regression models were used to test the significance of the slopes of the covariates with food intake.

Data Collection Summary:

Timing of Measurements

After screening for eligibility, subjects were measured for height and weight and completed several questionnaires.  Subjects ate breakfast, lunch and dinner in the lab on 3 separate occasions.

Dependent Variables

  • Eating Inventory
  • Eating Attitudes Test
  • Zung Self-Rating Depression Scale
  • Diet and Health Knowledge Survey
  • Visual analogue scales to measure hunger, thirst, perception of how much they could eat, nausea, and fullness
  • Asked to rate food sample on pleasantness of taste and texture, perceived fat content, perceived level of saltiness/sweetness and perceived calories in food

Independent Variables

  • Entree varied in energy density to be either 1.25, 1.50, or 1.75 kcal/g (5.23, 6.28, or 7.32 kJ/g) but held similar in macronutrient composition and palatability.  On each day, entrees at all 3 meals had the same energy density and were consumed ad libitum.   Subjects instructed to consume only food or beverages provided by lab, refrain from drinking in prior 24 hours, maintain similar exercise schedules.
  • Subjects assigned to 1 of 2 groups:  1 group received nutrition label with each meal showing energy density, the other group received no nutrition information.  Prior to experimental sessions, subjects in information group received nutrition training and brief quiz to assess understanding.

Control Variables

 

Description of Actual Data Sample:

Initial N: 42 women qualified for participation

Attrition (final N):  40 females completed.  1 dropped from study for not eating minimum required food intake.  1 withdrew for personal reasons.  20 in each group.

Age: No info:  mean age 20.5 +/- 3.1 years; Info:  mean age 21.8 +/- 2.7 years

Ethnicity:  Not mentioned

Other relevant demographics:  No info BMI: 21.9 +/- 1.2, Info BMI: 22.1 +/- 1.7 

Anthropometrics:  Groups did not differ significantly in any of the subject characteristics 

Location: Pennsylvania State University

 

Summary of Results:

 

Info group (kcal/g) of total diet No info group (kcal/g) of total diet
Low energy density 1.32 +/- 0.004 1.32 +/- 0.005
Medium energy density

1.51 +/- 0.009

1.50 +/- 0.001

High energy density

1.69 +/- 0.005

1.68 +/- 0.004

Other Findings

Subjects in both groups had the same pattern of food intake across the 3 levels of energy density.

Energy density significantly affected food intake; subjects in both groups combined consumed 22% less energy in the low energy density condition than in the high energy density condition (p < 0.0001).

There were no significant differences between groups on ratings of hunger, nausea, fullness, pleasantness, perceived fat and calorie content, nutrition knowledge.

Author Conclusion:
In conclusion, the energy intake of normal-weight women in both groups increased as the energy density of their meals increased.  Thus, results of this study suggest that energy density can have a significant influence on energy intake, even when individuals are informed about the energy density of their meals.
Funding Source:
Government: NIH
Reviewer Comments:
Well controlled study - food provided in lab.
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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? 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
  2.2. Were criteria applied equally to all study groups? 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? 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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? N/A
  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.) 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
  4.1. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? 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
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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  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? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  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
  7.1. 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
  7.3. 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
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? 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
  8.1. 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
  8.3. 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
  8.5. 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
  8.7. 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
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes