MNT: Weight Management (2015)
- Determine whether small-group nutrition education sessions led by a RD added to an internet-based work site wellness program would facilitate weight and fat mass loss
- Examine racial differences (black and white) in response to the study intervention.
- Overweight (BMI from 25kg/m2 up to 30kg/m2) and obese (BMI of 30kg/m2 or more)
- Non-diabetic (fasting glucose under 126)
- Employees of the National Institutes of Health
- Self-identified as healthy and not active in exercise or weight-reduction programs.
- Anemia (hemoglobin under 11)
- Liver, kidney or thyroid disease
- Recent (within two months) initiation of prescription medication.
Participants were recruited by National Health Institute campus announcements.
Participants were randomly assigned to one of two groups:
- WI+GS: Internet wellness information combined with nutrition education group sessions
- WI: Internet wellness information alone.
Intervention was six months in duration. Primary end-points of the study were differences in weight reduction between the WI+GS and WI Groups from baseline to three months and to six months' follow-up. Secondary outcomes included: Changes in total fat mass, truncal fat, abdominal and hip circumferences, lipid levels, insulin sensitivity and exercise performance from baseline to six months.
Investigators were blinded to randomized assignment.
WI+GS and WI Groups:
- All participants were provided internet-based wellness information created by the NHLBI for employees that included recommendations from the Department of Health and Human Services and the USDA
- Each subject was given a pedometer with instructions to increase average daily step count by 5,000 steps over their baseline average and were given card-key access to private fitness rooms located on campus
- Participants were also encouraged to continue physical activity on non-work days.
- Participants in the WI+GS Group were instructed to attend nutrition education sessions in small groups (10 persons or fewer per session) conducted by a RD
- The first three months of the group education sessions consisted of a 12-week curriculum based in part on NHLBI’s Aim for a Healthy Weight Program. Each session was 45 minutes and included a private weigh-in, homework questions related to the previous sessions to be discussed by attendees and a presentation on nutrition information relevant to weight management and cardiovascular health.
- After three months, participants transitioned to monthly classes for the remaining three months, which also included weigh-ins conducted by an RD, with focus on weight loss maintenance
- Before the initial group session, participants met privately with the RD to set weight loss goals. The RD provided an individualized calorie level and a daily meal plan. The RD encouraged participants to keep daily food journals throughout the study.
- Intention-to-treat analysis was performed for subjects who withdrew from the study after at least the three-month weight measurement
- T-tests or Mann-Whitney-Wilcoxon test for continuous data and the X2 proportionality test were performed
- Pearson’s correlation or Spearman’s rank correlation were performed for associations between frequency of attendance at group sessions and weight or fat mass loss
- Separate repeated-measures mixed-effects models were fit for outcomes
- Adjusted models were evaluated to determine the treatment effect, time effect and the treatment x time interaction effect
- A P-value of no more than 0.05 was considered statistically significant
- The study had 80% power at a two-sided type I error of 0.05 to detect a difference in weight change between the WI+GS and WI Groups of two kg, assuming a population standard deviation of three kg and a withdrawal rate of 30%.
Timing of Measurements
- Weight was measured at baseline, three months and six months
- Waist circumference, hip circumference, fasting blood work (glucose, insulin and lipids), total fat mass and percentage truncal fat were measured at baseline and six months
- Exercise performance was measured at baseline and five months.
- Fat mass
- Truncal fat
- Abdominal circumference
- Hip circumference
- Exercise duration
- Peak VO2
- Insulin sensitivity (HOMA)
- Total cholesterol
WI+GS or WI.
Participants were asked to maintain a diary of daily pedometer counts throughout the study.
- 199 (199 females, no males)
- WI+GS Group: 99
- WI Group: 100.
Attrition (Final N)
- WI+GS Group: 69
- WI Group: 70 (30% dropout rate).
- WI+GS Group: 47±9 years
- WI Group: 45±12 years.
- WI+GS Group: 56% black, 33% white, 4% Asian, 7% Hispanic
- WI Group: 59% black, 34% white, 1% Asian, 6% Hispanic.
Other Relevant Demographics
There were no significant differences in demographics between WI+GS and WI Groups.
- Average BMI for the group was 33.9±6.3kg/m2 (range, 25.0-57.7)
- There were no significant differences in clinical characteristics between the WI+GS Group and the WI Group.
- WI+GS subjects lost more weight than WI subjects at three months (-2.2±2.8kg vs. -1.0±3.0kg, P=0.009 for treatment x time interaction)
- Weight loss at six months was significant for the WI+GS and WI Groups (-2.7±3.9kg vs. -2.0±3.9kg, P<0.001) but the difference between groups was not significant (P=0.436 for treatment x time interaction)
- WI+GS and WI Groups had significant improvements in fat mass (-2.2kg), truncal fat (1.8%), abdominal circumference (-3.4cm), hip circumference (-2.4cm), exercise duration (+47 seconds), peak VO2 (1.7 ml O2 kg-1 per minute-1), HOMA, total cholesterol, LDL and triglycerides (all P<0.05), but without significant difference between WI+GS and WI Groups
- Similar proportions of black and white people completed the study (67% vs. 74%, P=0.303)
- Time effect for weight loss was significant for black women and white women at three and six months (P<0.001). Irrespective of group, race x treatment interaction was not statistically significant for weight loss at three months (P=0.816) or at six months (P=0.819).
- The time effect for adiposity, exercise performance, insulin sensitivity and blood lipids was statistically significant for both races (all P<0.05), however the race x treatment interaction was not statistically significant and there was no statistically significant differences in improvement in outcomes by race (all P>0.05).
- Overweight women provided with internet-based wellness information and exercise resources at the work site lost weight and fat mass, with similar achievement by black and white women
- The additional weight loss benefit of nutrition education sessions, apparent at three months, was lost by six months and may require special emphasis on subjects who fail to achieve weight loss goals to show continued value.
|Government:||National Heart, Lung, and Blood Institute; the National Institute of Diabetes, and Digestive and Kidney Diseases; the Clinical Center, National Institutes of Health|
- Large racially diverse population
- High dropout rate
- All RDS were white; nutritional instruction may not have been of value to majority of black participants
- Continuation of weekly nutrition education sessions might have facilitated continued weight loss in the WI+GS Group
- The longer study period may have favored the WI+GS Group
- Greater weight loss may have been achievable by use of portable devices to self-monitor diet and physical activity
- Motivational interviewing was not used and has been reported to be effective in several weight loss trials.
Quality Criteria Checklist: Primary Research
|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|
|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?||Yes|
|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?||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)?||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?||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|