Mayer-Davis EJ, D'Antonio AM, Smith SM, Kirkner G, Martin SL, Parra-Medina D, Schultz R. Pounds off with Empowerment (POWER): a clinical trial of weight management strategies for black and white adults with diabetes who live in medically underserved rural communities. Am J Public Health. 2004;94:1736-1742.PubMed ID: 15451743
To develop, implement, and evaluate a 1-year primary care-based lifestyle intervention for weight management that was designed to improve metabolic control among individuals who have type 2 diabetes and live in rural medically underserved communities.
- 45 years or older with clinical diagnosis of diabetes
- BMI 25 kg/m2 or greater during previous calendar year
- Any limitation that would prohibit full participation in the study (e.g. metastatic cancer, multiple or recent [within 6 months] myocardial infarction or stroke, dialysis for end-stage renal disease, severe psychiatric disease or dementia, or inability to walk)
Potentially eligible participants were identified through diabetes registries at each health center. An introductory letter cosigned by the health center's medical director and the study's principal investigator was sent to eligible potential study participants; this was followed up with a recruitment and eligibility-screening phone call.
Randomized clinical trial.
Blinding used (if applicable)
Assumed for laboratory measures
Intervention (if applicable)
- Intensive-lifestyle intervention: modified from the life-style intervention of the DPP (Diabetes Prevention Program); regular use of group sessions, considerable simplification and reduction in the amount of written materials, encouragement of physical activity at low to moderate intensity for individuals who had very sedentary lifestyle and inclusion of additional regionally/culturally appropriate examples. Participants met weekly with the study nutritionist for delivery of the first 4 months of the core curriculum (intensive), every other week for the next 2 months (transition), and once a month for the remaining 6 months (maintenance). Sessions were modeled after the NIH-funded Trial of Non-Pharmacologic Interventions in the Elderly and were conducted sequentially in a pattern of 3 group sessions and 1 individual session.
- Reimbursable-lifestyle intervention: condensed version of the intensive-lifestyle intervention, in which key elements of the intensive-lifestyle intervention were delivered in 4 1-hour session over the course of the 12-month study and included 3 group sessions and 1 individual session. The total time allotted for delivery was determined by the approximate number of hours reimbursed annually be Medicare for diabetes education (diet and physical activity) in South Carolina for an individual who was recently diagnosed with diabetes.
- Usual care: delivered in 1 individual session by a study nutritionist at the beginning of the 12-month period. Information related to diet and physical activity was derived from materials developed by the American Diabetes Association and the American Dietetic Association.
- Sample size was determined by the sample size formula for group randomization proposed by Donner. The sample size (n=50 per group) allowed detection at alpha=0.05 of a 6% weight loss at the end of the study, with 80% power, for intensive-lifestyle intervention versus usual care and for reimbursable-lifestyle intervention versus usal care.
- Intervention effects were first evaluated with paired t tests within each randomization group.
- Differences between interventions and usual care were evaluated with linear regression modeling of weight change that accounted for clinical site and for change in use of prescribed diabetes medicaiton (insulin, metformin, and other oral hypoglycemic agents) during the course of the 1-year intervention period.
- Models did not require adjustment for education, gender, or age because these did not differ significantly between randomization groups at baseline.
- Additionally, between-group differences were evaluated with random effects and repeated-measures regression modelis in SAS PROC MIXED, with specification of random clinic effects within random subject effects that allowed for missing values from follow-up visits. The results of these analyses were similar to the regression modeling, thus only the regression model results are presented in the results section.
- To eliminate the possibility of health center differences in intervention delivery, we tested the interaction between clinic and randomization group, and no such interactions were detected.
- Analyses were repeated in the subgroup of study participants ("high attendees") who attended at least 50% of the core curriculum and transitional sessions for intensive-lifestyle intervention (n=36) or at least 2 of the 4 sessions for reimbursable-lifestyle intervention (n=47).
Timing of Measurements
Standardized measurement visits occurred during the randomization visit and during visits scheduled at 3 months, 6 months, and 12 months after randomization.
- Weight loss: weight was measured to the nearest 0.23 kg (0.5 lb) with a Detecto balance beam scale that had a stadimeter.
- Height was measured to the nearest 0.1 centimeter while the participants stood erect, looking forward, against the stadimeter after taking a full inspiration.
- BMI was calculated as kg/m2
- Lipid profile
- Blood pressure: measured three times with a standard mercury sphygmomanometer; the averages of the second and third readings for systolic and diastolic pressure were included in the statistical analysis.
- Usual care
- Reimbursable-lifestyle intervention
- Intensive-lifestyle intervention
- Clinic site
- Diabetes medications
Initial N: 187
Attrition (final N): 152 (81%) were retained through the 12-month end-of-study measurement visit (122 women; 30 men)
- usual care: n=56
- reimbursable-lifestyle intervention: n=47
- intensive-lifestyle intervention: n=49
Age: average age was 60 years
Ethnicity: overall 82% black
- usual care: 73.2% black; 26.8% non-hispanic white; 0% other
- reimbursable-lifestyle intervention: 89.4% black; 10.6% non-hispanic white; 0% other
- intensive-lifestyle intervention: 83.7% black; 14.3% non-hispanic white; 2.0% other
Other relevant demographics:
Education (% with less than high school)
- usual care: 60.0%
- reimbursable-lifestyle intervention: 44.7%
- intensive-lifestyle intervention: 38.8%
Anthropometrics and Disease Information
Usual care Reimbursable-lifestyle intervention Intensive-lifestyle intervention Body mass index, kg/m2 35.2 (7.5) (mean; SD) 37.6 (6.5)
Diabetes duration, y
Diabetes treatment, %
Oral hypoglycemic only
Combination insulin, orals
No diabetes medication
Body mass index, kg/m2
35.2 (7.5) (mean; SD)
None of the measured baseline characteristics differed significantly among interventions groups at baseline (all P>0.05).
Two primary health care centers in rural counties (South Carolina) that had large numbers of patient visits for diabetes care.
Table 2 Change in secondary outcomes between randomization and 6 months
Usual care (n=56)
Reimbursable-lifestyle intervention (n=47)
Intensive-lifestyle intervention (n=49)
|change (Paired t test P; versus Usual care P))|
Body mass index
|-0.161 (NS)||-0.296 (NS; NS)||-0.974 (<0.001; <0.01)|
|HbA1c||-1.12 (<0.0001)||-0.843 (0.05; NS)||-1.56 (<0.0001; NS)|
Total cholesterol (mg/dL)
-0.03 (NS; NS)
-0.09 (NS; NS)
LDL cholesterol (mg/dL)
-1.44 (NS; NS)
-3.37 (NS; NS)
|HDL cholesterol (mg/dL)||-1.12 (NS)||1.58 (NS; NS)||0.73 (NS; NS)|
|Triglyceride (mg/dL)||0.91 (NS)||0.83 (0.0067; NS)||0.87 (NS; NS)|
|Systolic blood pressure (mm Hg)||-9.52 (<0.0001)||-4.26 (NS; NS)||-3.31 (NS; NS)|
|Diastolic blood pressure (mm Hg)||-2.65 (NS)||-0.07 (NS; NS)||-0.49 (NS; NS)|
- Paired t tests within each group at 6 months showed statistically significant weight loss between randomization and follow-up among intensive-lifestyle participants (P<0.0001) but not among reimbursable-lifestyle or usual-care participants.
- Regression analyses showed that weight change at 6 months was significantly greater among intensive-lifestyle participants compared with usual-care participants (P<0.01).
- Although some regain of lost weight was observed at 12 months, weight loss among intensive-lifestyle participants of 2.2 kg was significantly different from baseline (P<0.003).
- Weight loss among men and women in the intensive-lifestyle group was comparable at 3 and 6 months (P>0.05); however, at 12 months, mean weight loss among men was 4.7 kg compared with 1.5 kg among women (P=0.02). Weight loss of 2.2 kg at 12 months among the intensive-lifestyle participants compared with 0.3 kg among the usual-care participants (P=0.55) did not differ according to gender (P>0.05).
- Weight loss did not differ between reimbursable-lifestyle and usual-care participants at either 6 months or 12 months.
- Forty-nine percent of the intensive-lifestyle participants lost at least 2 kg compared with 25% of the usual-care participants; conversely, 12% of the intensive-lifestyle participants gained at least 2 kg compared with 27% of the usual-care participants (P<0.05). Reimbursable-lifestyle participants did not differ significantly from usual-care participants in these analyses.
- HbA1c declined by 1.1 points among usual-care participants (P<0.01), by 1.6 points among intensive-lifestyle participants (P<0.01), and by 0.8 points among reimbursable-lifestyle participants (P<0.05). Differences between groups were not statistically significant.
- In the intensive-lifestyle intervention, 36 (73%) attended at least 50% of the core curriculum and transition sessions, and all 47 individuals in the reimbursable-lifestyle intervention attended at least 2 of the 4 sessions; all usual-care participants were included for comparison. Among these intensive-lifestyle "high attenders", mean weight loss at 6 and 12 months was 3.1 kg (P<0.001 compared with usual-care participants) and 2.7 kg (P<0.05 compared with usual-care participants), respectively.
- Attention to highly specific participant needs, including transportation, played an important role in achieving the overall retention rate of 81% and an attendance rate of 73% among intensive-lifestyle participants who were present for at least 50% of the intensive and transition sessions (i.e. at least 10 sessions).
Improvement in both weight and glycemia was attainable by life-style interventions designed for persons who had type 2 diabetes and lived in rural communities.
Limitations and other pertinent information cited by authors:
- Small number of men in the intensive-lifestyle intervention (n=11).
- While this trial was ongoing, a "diabetes collaborative" was introduced into both of the clinic sites as part of a federally funded effort to improve chronic disease management among community health center participants. Thus, improvement in day-to-day diabetes management, including consistency in taking prescribed diabetes medication and monitoring blood glucose at home, may have accounted for the improved glycemic control.
|University/Hospital:||Arnold School of Public Health, University of South Carolina|
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?||???|
|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?||???|
|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?||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?||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)?||No|
|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|