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Citation:

Jacobs DR Jr, Sluik D, Rokling-Andersen MH, Anderssen SA, Drevon CA. Association of one-year changes in diet pattern with cardiovascular disease risk factors and adipokines: Results from the one-year randomized Oslo Diet and Exercise Study. Am J Clin Nutr. 2009 Feb; 89(2): 509-517.


PubMed ID: 19116328
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
POSITIVE: See Research Design and Implementation Criteria Checklist below.
Research Purpose:
To study changes in dietary patterns relative to changes in body size, blood pressure and circulating concentrations of lipids, glucose, insulin, adiponectin and other cytokines, in the context of a one-year randomized intervention study.
Inclusion Criteria:
  • Adults aged 41 to 50 years of age
  • Physically inactive as measured by questionnaire (exercising at most once per week)
  • Body Mass Index (BMI) >24kg/m2
  • Diastolic blood pressure 86 to 99mm Hg
  • Total cholesterol 5.20 to 7.74mmol per L
  • HDL cholesterol <1.20mmol per L
  • Triglycerides >1.4mmol per L.
Exclusion Criteria:
  • Overt cardiovascular disease
  • Diabetes
  • Taking anti-hypertensive drugs
  • Taking acetylsalicylic acid
  • Taking other drugs that might interfere with test results
  • Already on a lipid-lowering diet
  • Already engaging in regular endurance training two times or more per week
  • Persons with diseases or personal traits that make them unsuited for participation
  • Persons who refuse to sign the declaration of willingness. 
Description of Study Protocol:

Study Description

  • Data were from the Oslo Diet and Exercise Study (ODES) 
  • Participants were randomly allocated to four intervention groups:
    • Diet
    • Exercise
    • Diet and exercise
    • Control. 

Conditions

  • Diet:
    • The diet intervention included dietary counseling with the participant, while the participant's spouse was present
    • Counseling occurred at baseline, month three and month nine
    • Counseling was tailored to the participant's dietary habits and risk factor profile. Key points were:
      • Spread energy intake across the day
      • Increase consumption of fish and fish products, vegetables and fiber-rich foods
      • Decrease consumption of sugar and saturated fat
      • Moderate salt consumption
  • Exercise: The exercise program entailed supervised group workouts, such as aerobics, circuit training and fast walking and jogging one hour per session three times per week
  • Control: There was little contact with the control group during the year-long intervention period.

 Study Duration

12 months; measures were collected at baseline and 12 months.

Location

Norway.

Data Collection Summary:

Dietary Assessment Method

A five-page optically readable 180-item food-frequency questionnaire (FFQ), which had been previosly validated (Andersen et al, Nr J Nutr. 2005; Andersen et al, Am Epidemiol. 1999).

Dietary Index/score Used

An a priori diet score created by summing tertile rankings of 35 food group variables.

  • Theoretical score range: Zero to 62
  • Observed score range: 15 to 47.

Brief Description of Index/score Components

  • An a priori diet score was created by summing tertile rankings of 35 food group variables (e.g., whole grain breads, fruit, eggs, chicken)
  • This score was based on a concept originally proposed by Steffen et al. (2005)
  • Food groups were postulated to be beneficial (N=22), neutral (N=4) or adverse (N=9) for health
    • For each food group postulated to have a benefit, the a priori diet score received two points for being in the highest tertile, one point for being in the middle tertile and zero points for being in the lowest tertile
    • For each food group postulated to be adverse, the a priori diet score received zero points for being in the highest tertile, one point for being in the middle tertile and two points for being in the lowest tertile
    • Food groups rated as neutral did not contribute to the a priori diet score
  • Theoretical score range: Zero to 62
  • Observed score range: 15 to 47.

Outcomes Measured

Change in:

  • Body weight
  • Waist circumference
  • Percentage body fat
  • Leptin
  • Adiponectin
  • Systolic blood pressure
  • Diastolic blood pressure 
  • Total cholesterol
  • LDL-cholesterol
  • HDL-cholesterol
  • Triglycerides
  • Fasting glucose
  • Fasting insulin
  • Insulin after glucose challenge
  • Resistin
  • IL-6
  • IL-8
  • TNF-alpha
  • CRP
  • HGF
  • NGF
  • PAI-1.

Methods of Outcome Assessment

All outcome variables were measured (not self-reported):

  • Body weight was measured by using a balance scale
  • Height was measured using a standing stadiometer
  • Waist circumference was measured while the subjects were standing
  • Percentage body fat was measured with a near-infrared spectrophotometry technique
  • Supine blood pressure was measured in triplicate with an automatic oscillometer
  • Blood samples were drawn between 8:00 a.m. and 10:00 a.m. after the subjects had fasted and abstained from smoking overnight
  • Cholesterol, Triglycerides and glucose concentrations were derived with enzymatic methods
  • HDL-cholesterol was measured with a Heparinmanganese method
  • LDL-cholesterol was estimated by using the Friedewald equation
  • Insulin was measured using a radioimmunoassay method
  • Factor VII activity, adipokines, cytokines, growth factors, CRP and PAI-1 were analyzed in the laboratory.
Description of Actual Data Sample:
  • Sample size:
    • Initial N: 219 (198 men, 21 women)
    • Final N: 188 (all men; the 21 women completed all measures, but were excluded because the sample size of women was too small)
    • Attrition (%): 95%
  • Age: 45±2.5 year
  • Gender: 0% female
  • Race/ethnicity: Norwegian, otherwise not reported
  • Baseline weight status:
    • Weight: 91±12.5kg
    • Waist circumference: 103±9.0cm
    • Body mass index: 28.6±3.4kg/m2
    • Percentage body fat: 24.4%±3.4%
  • Baseline distribution of dietary patterns:
    • Energy intake: 10.6±2.9mJ per day
    • A priori diet score: 31±6.5.
Summary of Results:

Results Related to Change in Body Weight

  • Weight significantly decreased in the diet only groups; weight loss was 5kg to 7kg in the diet groups and 2kg in the exercise only group
  • A 3.5kg weight loss per 10-point increase in diet score was noted for all intervention groups.

Results Related to Waist Circumference

  • Waist circumference significantly decreased in the diet only groups; decrease in waist circumference was 5cm to 7cm in the diet groups and 3cm in the exercise only group
  • A 3cm waist circumference decrease per 10-point increase in diet score was noted.
Results Related to Percent Body Fat

Percentage body fat mass significantly decreased in the diet and exercise groups; decrease in percent body fat as 1% to 2% for each intervention group and per 10-point change in diet score.

Confounders
Total Energy Intake Physical Activity Baseline BMI Sex Age Alcohol Intake Other
x    

x

Only males

x   Smoking, diet score

 

Author Conclusion:
  • On the basis of change in a clinically relevant a priori diet score, the authors found change in body size (weight, percent body fat, waist circumference) and biochemical markers over the one-year randomized clinical trial of diet and exercise
  • This study showed a beneficial effect of change in diet score on change in weight, waist circumference, body fat, systolic blood pressure and plasma concentrations of total and LDL-cholesterol, fasting glucose, fasting and post-load insulin and leptin, independent of energy intake and the intervention group the subjects were in.

Strengths and Limitations

Strengths

  • Ability to evaluate the reversibility of changes in body size and biochemical markers
  • Observational study was embedded in a randomized trial, allowing authors to see change in diet that was more varied than would generally be seen in free-living subjects and diet was carefully monitored.

Limitations

  • Conducted in men only in a particular cultural context
  • The sample studied was restricted to those who were eligible for the randomized study
  • Could not adjust for socioeconomic status because they did not measure it.
Reviewer Comments:

Not familiar with all of the funding sources or classification.


Research Design and Implementation Criteria Checklist: Primary Research
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 used? (Concurrent preferred over historical controls.)
Yes
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
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?
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
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
  6.3. 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?
No
  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?
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
  7.2. 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)?
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
  8.7. If negative findings, was a power calculation reported to address type 2 error?
No
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