DM: Effectiveness of MNT Provided by RD/RDN (2015)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine whether a community-based, group-centered public health intervention addressing nutrition and exercise can ameliorate glycemic control and associated cardiovascular risk factors in type 2 diabetic patients in rural Costa Rica.
Inclusion Criteria:

Type 2 diabetes had been diagnosed (defined by fasting plasma glucose concentration greater than or equal to 126 mg/dl) established through chart review or consultation with treating physician.

Exclusion Criteria:
No potential volunteers were excluded.
Description of Study Protocol:

Recruitment -

  • A list of known diabetic patients was generated by the hospital's infomatics department.
  • The social worker and health technician assigned to each community supplied a list of patients with diabetes.

The above individuals were invited to attend informational meetings to explain what the study would entail.

  • Additional publicity in the communities included posters in public buildings and buses, announcements in churches, on a local radio station, and via a car-mounted megaphone.


Participants with type 2 diabetes were randomly assigned to the intervention or control group. All participants received basic diabetes education in the form of a lecture that reviewed type 2 diabetes and its symptoms, treatment, and associated complications.

The subjects in the intervention group participated in a 12-week lifestyle intervention program, with 11 weekly nutrition classes (90 minutes each session).  Participants for whom exercise was deemed safe also participated in triweekly walking groups (60 minutes eash session).

The control group were informed that that they would be offered a similar program at the end of the study.

Blinding used (if applicable)  

  • not applicable to participants, nutrition educators, or walking group leaders
  • technicians who preformed baseline and endpoint measures were blinded to treatment group assignement
  • Participants' physicians were informed that they were in the study, but not which group they were in.

Intervention (if applicable)

The subjects in the intervention group participated in a 12-week lifestyle intervention program, with 11 weekly nutrition classes (90 minutes each session) in centrally located community centers. Classes were taught by 3 nutritionists enrolled in an MS program, who received instruction in the specific dietary curriculum that was used in the study and helped refine it to local customs. Each class was offered twice a week, limited to 15 individuals, and subjects were encourged to bring family members. Course focused on portion control, use of healthier food substitutes, food groups, the difference between simple and complex carbohydrates and relation to glycemic index and fiber content, the difference between fats and relation to cholesterol and atherosclerosis, sources of protein and fat content, hidden calories in beverages, and micronutrient and fiber content of fruits and vegetables. Subjects set weekly goals, shared these at the end of class, and reported progress at the next week.

Participants for whom exercise was deemed safe also participated in triweekly walking groups (60 minutes eash session). Local community volunteers organized and led the groups, and subjects were encourged to bring their families. Safe footwear and foot self-examination were taught.

Statistical Analysis

Two sided homoscedastic t tests were used to analyze the differences between the intervention and control groups in changes from baseline to endpoint measures. All analyses were based on intent-to-treat principle. All results are shown as means ± SD, unless noted.

Data Collection Summary:

Timing of Measurements Baseline and endpoint (12 weeks).

 Dependent Variables

  • glycosylated hemoglobin
  • fasting plasma glucose
  • total cholesterol
  • triglycerides
  • HDL
  • LDL
  • weight
  • BMI
  • blood pressure

Independent Variables

  • Lifestyle intervention program

Control Variables - Physicians were asked to refrain from nonessential changes in medication and dosages that might affect study outcome measures. Any essential changes were implemented and reported to investigators.


Description of Actual Data Sample:

Initial N: 75

Attrition (final N): 61 (defined by missing the study end measurement day), 7 from control group and 7 from intervention group

Age: Intervention group 60 ± 10; control 57 ± 9

Ethnicity: not specified, but note location

Other relevant demographics: baseline demographic characteristics did not differ significantly between groups

Anthropometrics  baseline clinical characteristics did not differ significantly between groups

Location: 3 small communities surrounding Grecia (Rural Costa Rica)


Summary of Results:



Intervention Group            (n = 33)

Control group         (n = 28)

Confidence intervals


Chnage in weight (kg)

 -1.0 ± 2.2 0.4  ± 2.3  -2.48 to -0.15  0.028
Change in BMI (kg/m2)  -0.4 ± 0.9 0.2  ± 1.0 -1.06 to -0.08   0.022
Change in fasting plasma glucose  -19 ± 55 16  ± 78  -71.1 to -0.28 0.048 
Change in glycosylated Hemoglobin (%)  -1.8 ± 2.3  -0.4 ± 2.3  -2.52 to -0.15 0.028 
Change in serum lipids (mg/dl): - - - -
total cholesterol  -8 ± 36 1 ± 33 -27.05 to 8.67  0.31 
HDL cholesterol  -5 ± 5 -3  ± 6 -4.05 to 1.95   0.49
LDL cholesterol  5 ± 36 -1  ± 29 -12.43 to 24.02  0.53 
triglycerides  -48 ± 163 27  ± 176  -162.5 to 11.7 0.09 
Change in blood pressure (mmHg): - - - -
systolic  -5 ± 23 -4  ± 16  -10.75 to 10.06 0.95 


-7  ±9

-3  ±8

-8.57 to 0.24 


 Other Findings

The intervention group lost 1.0 ± 2.2 kg compared with a weight gain in the control group of 0.4 ± 2.3 kg ( P = 0.028).

Fasting plasma decreased in the intervention group and increased in the control group.

Author Conclusion:

This study provides evidence that a community-based nutrition and exercise intervention for type 2 diabetic patients, conducted in peer groups, can be effectively implemented in developing nations, and that important health indicators significantly improve. In particular, BMI and glycemic levels decreased.

This small scale study on the feasability of implementing an effective lifestyle modification program, initially conducted by nutritionists and members of the community, has the potential to be self-sustaining.

Funding Source:
Reviewer Comments:
Good discussion of problems in blinding, the limitations of small scale, and comparison with other recent randomized controlled trials in diverse communities.
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? Yes
  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.) Yes
  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? N/A
  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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  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