MNT: Weight Management (2015)

Citation:

Raatz SK, Wimmer JK, Kwong CA and Shalamar DS. Intensive diet instruction by registered dietitians improves weight-loss success. J Am Diet Assoc. 2008; 108 (1): 110-113.

PubMed ID: 18155995
 
Study Design:
Before-After 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 research was to determine how weight loss success due to a Registered Dietitian (RD)-led intervention compared with frequent weight monitoring.

Inclusion Criteria:
  • Subjects were overweight; BMI greater than 27kg per m2
  • Subjects were from first 28 enrolled in larger weight loss study.
Exclusion Criteria:
  • Prior signficant nutrition knowledge. One subject was excluded due to having a doctoral degree in nutrition.
  • BMI less than 27kg per m2.
Description of Study Protocol:

Recruitment

  • Subjects recruited for larger 11-week weight loss study
  • Specific recruitment techniques not given.

Design

  • Participants attended an initial screening visit to determine height, weight and BMI 
  • Dietary and physical activity estimates were made during an RD interview and clinical assessment of information was used to estimate energy needs. Total energy expenditure: BEE was calculated by Harris-Benedict equation, plus adjustments for reported activity and dietary intake.
  • Energy prescription was 750kcals below total energy expenditure 
  • Subjects participated in an 11-week program consisting of once weekly RD-led classes and semi-weekly weight checks
  • At the end of the 11 weeks, weight loss percent was evaluated on a continuous scale based on percent of RD and non-RD visits attended. 

Blinding Used

N/A 

Intervention

RD-led classes and weight checks. 

Statistical Analysis

  • Descriptive statistics were summarized within the entire group, by sex and by diabetes status and compared between subgroups
  • Means and standard deviations used for normally distributed data and Medians and range were used for non-normally distributed data
  • The two sample T- test and Mann-Whitney U nonparametric two-group comparison tests were used, as appropriate, for comparison between groups
  • Linear regression analysis were used to examine the relationships between RD-related visits and non-RD related weigh-in vists and weight loss (% weight loss)
  • Analyses were completed utilizing SigmaStat (Jandel Scientific, version 2.0, 1995, San Rafael, CA) to calculate the descriptive statistics and significance testing of variables and Minitab (version 14.20, 2005, State College, PA) was utilized to plot the fitted line regression of variables
  • The priori defined significance level for all statistics was set at 0.05.

 

Data Collection Summary:

Timing of Measurements

  • Beginning of study and end of 11-week intervention
  • Weights were checked semi-weekly throughout the study. Only the beginning and end of study weights were used for evaluation. 

Dependent Variables

  • Variable 1: Weight loss (% body weight)
  • Variable 2: Pre- and post-HbA1c (for subgroup who had diabetes).

Independent Variables

  • RD-led class visits
  • Weigh-in visits.

 Control Variables

  • Diabetic
  • Non-diabetic.
Description of Actual Data Sample:
  • Initial N: 28 (2 excluded prior to analysis)
  • Attrition (final N): 26 (10 men, 16 women)
  • Age: 43±12 years
  • Ethnicity: Not given
  • Other relevant demographics:
    • 8 had diabetes
    • Baseline HbA1c 7.2±1.0%
  • Anthropometrics: Baseline mean BMI 33.2±3.67kg per m2
  • Location: General Clinical Research Center of the University of Minnesota.
Summary of Results:

 

Variables

Treatment Group

Measures and Confidence Intervals

 Statistical Significance

 

Correlation to RD  Visits and Significance /

Correlation to Weigh-in Visits

Dependent  Variable 1

Weight Loss (kg)

% Weight Loss

Total group evaluated

3.8kg±2.9

4±2.7

Significance of weight loss for total group: P<0.001

r=0.451; P=0.021 /

r=0.329; P=0.101 (NS)

Dependent Variable 2

Change in HbA1c in Diabetes Group

 0

 Non-significant

 

 

Other Findings

  • The average number of RD visits was 8.8±2.7 out of 11 possible. The average number of weigh-ins (with no RD visit) was 19±5.5 out of 22 possible.
  • There were no differences in weight, BMI at the beginning or end of study between diabetic and non-diabetic subjects or between men and women.
  • Weight loss percent was significantly correlated with attendance of RD-instructed classes (r=0.451; P=0.021), but not attendance at weigh-ins that did not include RD-instructed classes (r=0.329; P=0.101).

 

Author Conclusion:
  • Frequent dietary instruction by an RD conveying topics related to weight loss was more effective than frequent weigh-in visits alone in promoting weight reduction in study participants
  • Results demonstrate that interaction with and education by an RD significantly improves weight-loss efforts, even when compared to frequent weigh-ins. Frequent weigh-ins is another factor related to weight-loss success that occurred more frequently in our study than RD contact. 
  • Future studies are needed to translate successful initial weight-loss strategies such as ours, into effective tools for long-term weight-loss sucess.
Funding Source:
University/Hospital: University of Minnesota
Reviewer Comments:
  • This was a very simple study that only looked at weight loss and correlated it to RD-led education sessions and to weigh-ins without RD education
  • All the subjects in the study had access to both the RD sessions and weigh-ins. There was no randomization or blinding involved. 
  • It is possible that the subjects who attended more RD sessions and lost more weight were the more motivated subjects
  • In a randomized controlled study, better determination of the benefits of RD-led education vs. frequent weigh-ins could be made 
  • This study is of limited value since it was not randomized and controlled.
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? ???
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? 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? 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? 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? Yes
  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? 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)? No
  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