Adult Weight Management

AWM: Eating Frequency and Patterns (2013)

Citation:

Kent LM, Worsley A. Trends in BMI, diet and lifestyle between 1976 and 2005 in North Sydney. Asia Pac J Clin Nutr 2009; 18 (3): 453-461.

PubMed ID: 19786395
 
Study Design:
Trend Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to provide a detailed examination of changes in BMI, diet and lifestyle among middle to high SES individuals in Australia during the last 30 years and to understand some of the dietary and behavioral antecedents of BMI in specified time periods between 1976 and 2005.

Inclusion Criteria:

Male and female individuals from the northern Sydney, Australia area

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

  • People from the northern Sydney area were invited to participate in a heart health screening
  • Invitations were from an advertising campaign involving local churches, electronic media, newspapers and hospital services.

Design

Trend study; cross-sectional data were selected from a series of biennial biomedical surveys to provide detailed examination of the associations of diet and lifestyle with BMI.

Blinding used

Implied with measurements

Intervention

Not applicable

Statistical Analysis

  • Logistic regression was performed to compare the changes in the proportion that were overweight or obese between 1976 and 2005
  • Bivariate analyses were conducted to examine the relationships between respondents' BMI and a series of variables
  • Pearson's r was used to assess the relationships between BMI and continuous variables
  • Spearman's rank-order correlation using two-tailed tests of significance was used to assess the relationship between nominal or ordinal variables likely to be associated with BMI
  • Data was analyzed using SPSS v 12.0 (Chicago, IL).

 

 

Data Collection Summary:

Timing of Measurements

  • Data from 1976, 1978, 1980, 1982, 1984, 1986, 1988, 1990, 1992 and 2005 were examined for changes in BMI
  • Data from 1994 to 2004 was not available due to logistic problems
  • Data from three years, approximately 10 years apart, were selected to provide detailed examination of the associations of diet and lifestyle with BMI: 1976, 1986 and 2005.

Dependent Variables

  • Height and weight were measured by hospital staff
  • Change in body mass index, which was calculated as weight (kilograms)/height (meters) x height (meters), with kg/m2. BMI was further dichotomized into normal weight (<25kg/m2) and overweight/obese (≥25kg/m2).

Independent Variables

  • Participants completed a food frequency questionnaire (FFQ) once in 1976 that contained 42 different food and drink items. The questionnaire was replicated in 1986 with the addition of fish and cream. The 2005 questionnaire included variables from previous years but scaled down the variety of meats, milks and dessert foods.
  • Participants completed a physical activity questionnaire in 1976 and 1986 that included the frequency of participating in walking, running, cycling, swimming, tennis, vigorous gardening and other vigorous activity per week. The 2005 questionnaire was also completed but the respondents had to record the frequency of exercise per week and time of each exercise session and intensity (low, moderate, high).
  • Hours of sleep per night
  • Smoking status (current, past and never smoked)
  • Frequency of alcohol consumption
  • Number of drinks consumed per sitting (1976 and 1986) or per day (2005). 

Control Variables

  • Age
  • Sex
  • Education
  • Occupation status
  • Marital status.
Description of Actual Data Sample:
  • Initial N: 2,064 men and 1,728 women from 1976-2005
    • 384 men and 338 women in 1976
    • 160 men and 146 women in 1978
    • 166 men and 141 women in 1980
    • 164 men and 142 women in 1982
    • 177 men and 13 women in 1984
    • 239 men and 227 women in 1986
    • 210 men and 225 women in 1988
    • 165 men and 148 women in 1990
    • 138 men and 167 women in 1992
    • 270 men and 62 women in 2005
  • Attrition (final N): As above
  • Age: Men had a mean age range from 1976-2005 of 43.6 years to 49.7 years; whereas women had a mean age range of 43.5 years to 51.4 years from 1976-2005
  • Ethnicity: Not described
  • Other relevant demographics: Some of the sample included Seventh-Day Adventists
  • Anthropometrics:
  • Location: Sydney, Australia.

 

Summary of Results:

Key Findings

  • Mean BMI increased in the early 1990s
  • For men, there was a 1.6 fold increase in the risk of being overweight or obese in 1990 compared to 1976; a 2.2 fold increase in 1992 P<0.001, and a 2.4 increase in risk of being overweight in 2005 P<0.001.
  • For women, there was a 1.6 fold increase in the risk of being overweight in 1990 and a 3.8 fold increase in the risk of being overweight in 1992 P<0.001. Women's risk of overweight decreased in 2005 compared to 1976, however this was not significant (P=0.157). 
  • Both men and women consumed eggs, spreads, extra foods, whole milk, grains, vegetables and fruit less frequently in 2005 than in previous years
  • Cola and alcohol were consumed more frequently by both sexes in 2005 than in previous years
  • For men, those who reported eating between meals once or twice a day had higher BMIs than men who never ate between meals
  • Salt, coffee, cola, alcohol and meat consumption, dieting to lose weight and eating between meals were positively associated with BMI while physical activity, food variety, large breakfasts and consumption of spreads were negatively associated
  • In terms of energy expenditure, minimal changes in frequency were observed over the three time periods among both men and women.
Author Conclusion:

Middle to high SES Australians in the late 20th and early 21st centuries embraced the affluent energy-dense dietary and sedentary lifestyle and moved away from the principles of a traditional (prudent) lifestyle advocated in the dietary guidelines. Food consumption and daily activities have important associations with BMI, though their specific associations differ by sex. Affluent lifestyle patterns appear to contribute to higher BMI, while a more prudent lifestyle seems to protect from such increases. 

Funding Source:
Industry:
Sanitarium Health Food Company
University/Hospital: Deakin University, Melbourne, Australia
Not-for-profit
Australian Research Council
Other non-profit:
Reviewer Comments:

Authors note the following limitations:

  • First, changes were made to the questionnaire by the hospital on four occasions over the 30-year period. This made it difficult to maintain continuity in variables that showed associations with BMI.
  • Other limitations include the cross-sectional nature of the surveys and the voluntary nature of the recruitment strategy.
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) N/A
  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) N/A
 
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? ???
  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? No
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? 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
  3.3. 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? 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? 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? Yes
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  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? N/A
  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
  6.4. 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
  6.6. 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? No
  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? No
  7.5. Was the measurement of effect at an appropriate level of precision? No
  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)? 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