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MNT: Weight Management (2015)


Tol J, Swinkels IC, deBakker DH, Seidell J, Veenhof C. Dietetic treatment lowers body mass index in overweight patients: An observational study in primary health care. J. Hum Nutr and Diet. 2014; 27(5): 426–433.

PubMed ID: 24205956
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To observe changes in body mass index (BMI) in overweight patients from primary clinics that received treatment by a dietitian. Factors associated with changes in BMI and sources of variability were explored.
Inclusion Criteria:
  • Registered dietitian (RD) working in private practices in primary health care in Netherlands
  • RDs had to use EVRY (Ensemble) software for documentation purposes.
Exclusion Criteria:
None applied.
Description of Study Protocol:


  • RDs were recruited for the National Information Service for Allied Health Care (LiPZ) study, 2005
  • Website advertisements were used to attract participant RDs
  • Survey was used to assess interest of RDs in participating in LiPZ.


  • Retrospective review of medical records from RDs included in LiPZ study. RDs provided dietetic treatment to patients and documented outcomes such as changes in patient BMI
  • Participating RDs registered patient information using EVRY software, which is used to record patient treatment and reimbursement information
  • Data were entered into database after appropriate quality control measures
  • Missing or inconsistent data were adjusted and corrected for and data were then submitted by the RDs.

Statistical Analysis

  • Descriptive statistics used to summarize sociodemographic, health and treatment characteristics of patients included in the study
  • Multivariate techniques (multi-level linear regression) used to assess sources of variability in BMI changes (patient level and RD level) and factors associated with a change in BMI
  • Five regression models :
    • Model Zero: Intercept only
    • Model One: Adjusted for age, gender, education level and previous dietetic treatment
    • Model Two: Adjusted for above plus communication and psychological barriers, cardiovascular disease (CVD) risk factors
    • Model Three: Adjusted for above plus BMI at treatment start
    • Model Four: Adjusted for above plus treatment duration.


Data Collection Summary:

Timing of Measurements

 Duration of treatment based on the patient's first and last consultation, which varied from patient to patient (zero months to six months to 18 months).

Dependent Variables

Documented changes in BMI from first to last consultation. RDs entered patients' heights and weights in EVRY software and BMI was computed.

Independent (Predictor/Control) Variables:

  • Age
  • Gender
  • Education
  • Previous dietetic intervention
  • Communication barriers
  • Psychological problems
  • CVD risk factors
  • BMI at treatment start
  • Treatment duration.

Intervention Provided and Documented by RDs

  • RDs used the nutrition care process. No dietary intake data were collected.
  • There was the expectation that RDs provided nutrition advice based on the Dutch dietary guidelines. Energy restriction of 600kcal was used for weight management.
  • Treatment duration varied for patients by RD. Initial visits ranged 45 minutes to 60 minutes. Follow-up visits were from 15 minutes to 30 minutes. One-to-one counseling was used most often. A one-year follow-up period was the recommended guideline.
  • Reimbursement was made by the Dutch standardized primary health insurance for a maximum of four hours per year, which included direct and indirect treatment time.
Description of Actual Data Sample:
  • Initial N: At the start of the study period, there were 8,294 overweight patients. There were 6,237 patients with complete data on independent or predictor variables. There were 32 dietitian participants. 
  • Attrition (final N): There were 3,960 with complete data on both independent and dependent variables (48% of initial). There was wide variation from RD to RD regarding amount of missing data on dependent variables.
  • Age (mean SD): Aged 50.1 years (15.2 years) for complete data, 48.7 years (14.8 years)  for those with missing endpoint BMI (P<0.001)
  • Other relevant demographics: Of the participants, 36.2 % were male and 63.8% were female
  • Anthropometrics: BMI at treatment start was 31.5kg/m2 (4.7kg/m2) for those with complete data, BMI 32.3kg/m2 (5.2kg/m2) for those with missing endpoint BMI data (P<0.001)
  • Location: The Netherlands.
Summary of Results:

Key Findings

Mean Change in BMI

  • Treatment start: Of participants, 43.5% were in the BMI overweight category and 56.5 % were in the BMI obese category
  • Treatment end: Of participants, 6.2% were in the BMI normal category, 48.3% were in the BMI overweight category and 45.5 % were in the BMI obese category
  • Dietetic treatment was associated with a mean BMI decrease of 0.94kg/m2  using adjustments outlined in Model Four above (P<0.001).
Sources of Variability in BMI Change
  • The proportion of total variance explained in mean BMI change across patients was about 97% (0.974) with most of the variation explained by a higher BMI at start of treatment and when treatment lasted at least six months
  • The proportion of total variance explained in BMI change varied about 3% (0.026) between RDs (-1.41kg/mto -0.62kg/m2) (P<0.001)
  • 10.5% of variance in BMI change across patients and 29.8% of variance in BMI change between RDs was explained by Model Four variables (P<0.05).
Factors Associated With BMI Change
  • There was a -0.8kg/mreduction in BMI for those treated longer than six months
  • For each unit increase in BMI greater than 31.6kg/m2 at the start of treatment, there was a reduction in BMI of 0.06kg/m2
  • After adjustments in Model Four, BMI was decreased by 0.73kg/m2 in average to overweight patients, by 0.90kg/m2 in the obese and by 1.49 kg/m2 in the extremely obese (P <0.001).
Factor Associated With Change in BMI Regression Coefficient (SE) P-value
Had previous dietetic treatment 0.251 (0.0062 <0.001
Had psychological problems 0.192 (0.094) 0.040
No CVD risk factor (other than DM HTN, hypercholesterolemia)
Had CVD risk factor(s)   
0.254 (0.080)
0.162 (0.031)
BMI at treatment start -0.056 (0.005) <0.001
Treatment duration (zero months to six months reference)
   Seven months to 12 months
   One year to 1.5 years
   More than 1.5 years
-0.835 (0.059)
-0.829 (0.096)
-.862 (0.095)


Author Conclusion:
  • Dietetic treatment in a primary care setting lowers BMI in overweight patients
  • Average BMI change was similar between RDs
  • Patients with  initially high BMI and those treated longer than six months had more of a reduction in their BMI.
Funding Source:
Government: Dutch Ministry of Health, Welfare and Sport
Reviewer Comments:
  • There was variation in duration of diagnosis for each patient and variation in what was being provided as "dietetic treatment" because it was not operationalized well, and it was not known how consistently it was applied
  • There may be bias in outcome measure of BMI. it was not clear if height and weight were measured or self-reported
  • It was not clear if RDs were all trained sufficiently and consistently
  • There was limited information on races and the majority of patients were male.
  • Study results cannot imply cause and effect
  • There were differences between groups with and without message data.
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? No
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? No
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? No
2. Was the selection of study subjects/patients free from bias? No
  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? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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? ???
  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? 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.) N/A
  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? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? No
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  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? 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? 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? ???
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  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