AWM: Eating Frequency and Patterns (2013)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To assess the effect of providing a conventional snack (cereal bars) and a non-conventional snack (almonds) over a 12-week period on eating frequency, hunger rating, dietary intake, body weight, fasting glucose, insulin and blood lipids of overweight men in Scotland.

Inclusion Criteria:
  • Healthy Scottish men aged 25 to 50 years
  • Body mass index (BMI): 25 to 35kg/m2
  • Not on a special diet or weight loss diet program
  • No major illness.
Exclusion Criteria:

Adult Scottish men with a major illness or following a special diet or weight loss diet program 

Description of Study Protocol:


Subjects were recruited through press releases and advertisements in local newspapers.


  • Prospective cohort study
  • Subjects were systematically assigned to one of three intervention groups as they entered the study:  
    • Control (C)
    • Cereal bar (CB)
    • Almond snack (AS)
  • All three study groups were provided with healthy eating advice consistent with current public health messages
  • Height, weight, skinfold thickness, waist circumference and hip circumference measurements were obtained by the same researcher at baseline, six and 12 weeks
  • Body mass index (BMI), percentage body fat and waist to hip ratio (WHR) were calculated from the anthropometric measurements.


  • The intervention groups (CB and AS) received the following each day for 12 weeks: 
    • CB: Two cereal bars (30g each; high CHO)
    • AS: Two packages of almonds (28g each; high protein)
  • Subjects consumed the snacks at any time during the day
  • The control group (C) did not receive any snacks and was instructed to continue their habitual eating pattern
  • Dietary intake was assessed in all groups at baseline, six and 12 weeks by a four-day unweighed diet diary. Subjects recorded the date, time, quantity and description of the food consumed. The same four days were recorded at each time point.  
  • Portion sizes were estimated using Standard Food Portion Sizes (Maff, 1993) and the dietary intake data was analyzed using COMPEAT PRO, version 5.8 (Nutrition Systems Ltd, London, UK).  Nutrients that were analyzed included the following:  
    • Total energy intake
    • Protein
    • Total fat
    • Polyunsaturated fatty acid (PUFA)
    • Monounsaturated fatty acid (MUFA)
    • Saturated fatty acid (SFA)
    • Carbohydrates
    • Total sugars
    • Starch
    • Fiber
    • Alcohol
  • Macronutrient composition of the snack foods for the entire day:  
    • Almond snacks: 56g, 343kcal, 3.9g CHO, 30.9g fat, 11.8g protein
    • Cereal bars: 60g, 227kcal, 44.4g CHO, 4.7g fat, 3.0g protein.

Statistical Analysis

  • SPSS, version 12 was used for data analysis
  • Level of statistical significance was defined as P≤0.05
  • All data were reported as mean (SD) unless otherwise noted
  • For normally distributed variables, repeated measures analysis of variance (ANOVA)
  • For non-normally distributed variables, Friedman test was used to determine differences across the three time points and Kruskal-Wallis test was used to determine significant differences between groups
  • Post-hoc tests were used where significant
  • Blood samples were compared at baseline and 12 weeks using paired sample T-tests (normally distributed variables) and Wilcoxon signed ranks tests (non-normally distributed variables). One-way ANOVA (normally distributed variables) and the Kruskal-Wallis test (non-normally distributed variables) were used to detect significant differences between groups.
  • Under-reporting was determined by estimating individual basal metabolic rates multiplied by 1.1 (minimum physical activity factor). Subjects reporting energy intakes below this level were considered under-reporters (URs). 20 subjects (44% of the sample) were classified as under-reporters using this criterion. 
Data Collection Summary:

Timing of Measurements

Anthropometric measurements, visual analog scales to assess hunger levels, average eating episodes over four days and blood samples were obtained at baseline, six and 12 weeks.

Dependent Variables

  • Variable 1: Level of hunger, measured using visual analog scales (VAS). Mean scores were calculated for the four-day diet diary period.
  • Variable 2: Eating frequency (EF); an eating episode was defined as any episode that provided 210kJ (50kcal) or more. Drinks consumed without food were excluded. Mean EF were calculated for the four-day diet diary period.
  • Variable 3: Anthropometric measurements (body weight, height, skinfold thickness, waist circumference, hip circumference)
  • Variable 4: Fasting blood glucose, insulin and lipid levels were measured using venous blood samples.

Independent Variables

  • Four-day unweighed diet diary data
  • Snacks: Cereal bars (CB group), almonds (AS group). 

Control Variables

C group was not provided snacks and continued habitual eating pattern.


Description of Actual Data Sample:
  • Initial N: 45 male subjects
  • Attrition (final N): 36 male subjects
  • Age: Mean age for the entire sample (N=45) was 39.6 (6.9) years, with a range of 35 to 44 years
  • Ethnicity: Scottish
  • Anthropometrics: 
    • BMI: 29.8 (2.8) kg/m2
    • Anthropometric data, HR, EF and dietary intake were not significantly different between the three intervention groups at baseline
  • Location: United Kingdom.
Summary of Results:

Key Findings

  • No significant change in eating frequency within groups
  • The almond snack group had a significantly higher eating frequency compared to the control group (P≤0.05) and cereal bar group (P≤0.01)
  • There was a significant decrease in percentage of calories from CHO (P≤0.01) and a significant increase in percentage of calories from fat (P≤0.001) in the almond snack group over the 12-week intervention.

 Mean Anthropometric, Eating Frequency and Hunger Rating Measurements at 12 Weeks


Cereal bars (CB)

Mean (SD)

Almond Snack (AS)

Mean (SD)

Control Group (C)
Hunger rating per day 5.2 (1.8) 4.1 (0.9) 4.5* (1.6)
Eating frequency per day 4.7 (1.0) 6.3#^ (1.6) 4.7 (2.3) 
Body mass index (kg) 97.0 (10.1) 95.0 (8.10) 92.8 (8.2)
Body mass index (kg/m2) 30.2 (3.5) 30.1 (2.7) 28.8 (1.8)
Waist:hip ratio 0.95** (0.41) 0.93 (0.61) 0.935 (0.29)

*, ** Significantly different from baseline at P≤0.05, 0.01.

#^ Significantly different between C-AS and AS-CB groups, respectively, at P≤0.05, 0.01.

Other Findings

There were no significant differences within groups or between groups in fasting glucose, insulin, total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDH) and high-density lipoprotein cholesterol (HDL) (includes under-reporters). When the under-reporters were removed from the analysis, there was a significant increase in mean TC in the CB group (P≤0.05) and a significant decrease in mean TG in the C group (P≤0.01) over the 12-week period.


Author Conclusion:

In the short-term (12-week period) snacking on cereal bars or almonds did not result in weight gain for adult males. Snacking on almonds resulted in a higher eating frequency and a higher percentage of calories derived from fats (PUFA and MUFA) compared to snacking on cereal bars or no snacking.

Funding Source:
Other: Kellogg Group, almonds supplied by the Almond Board of California
Reviewer Comments:

Limitations of the study: 

  • Small sample size
  • No assessment of intervention compliance (i.e., consumption of snacks)
  • No assessment of taste preference for snacks (almonds and cereal bars)
  • Consumption of study snacks in addition to habitual diet may have affected EF and under-reporting by subjects (44% of the original sample).
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? 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.) 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? ???
  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? No
  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? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  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
  6.8. 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? No
  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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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