The LIFE study is an investigator-initiated trial sponsored by the National Center for Complementary and Alternative Medicine (NCCAM). The study was reviewed and approved by Kaiser Permanente Northwest's IRB, and all participants provided written informed consent. A complete description of the rationale, design, and methods for the LIFE study has been published elsewhere.(25
Briefly, the LIFE study is a two-phase trial examining two alternative strategies for maintaining weight loss. Phase I provided a nonrandomized, 6-month intensive
behavioral weight loss intervention to 472 adult participants. This intervention program included recommendations to reduce dietary intake by 500 calories per day, adopt an eating pattern consistent with the DASH dietary pattern,(26
) and increase moderate intensity physical exercise to at least 180 minutes per week. The DASH diet emphasizes fruits, vegetables, and low-fat dairy products, includes whole grains, poultry, fish, and nuts, and is reduced in fats, red meat, sweets, and sugar-containing beverages. As such, the DASH diet is reduced in total fat, saturated fat, and cholesterol, and increased in potassium, calcium, magnesium, fiber, and protein
Participants who lost at least 4.5kg during Phase I were eligible for Phase II, the randomized weight-loss maintenance portion of the study. In this phase, participants are randomized to one of two weight loss maintenance interventions, with follow up through eighteen months post initial study entry. This paper focuses on results from the Phase I weight-loss intervention. Results from the second phase of the LIFE study will be presented separately when they become available.
Participants were men and women aged 30 years or more, with a BMI of 30–50 but weighing less than 400 pounds. Medical exclusions included recent (within the previous two years) cardiovascular event, cancer treatment, or inpatient psychiatric hospitalization. Diabetics injecting insulin, individuals taking weight loss medications, and those who had undergone bariatric surgery or liposuction in the previous year were excluded. Additional exclusions included previous experience with acupuncture or acupressure for weight management, plans to leave the metropolitan area prior to the end of the program, weight loss of more than 20 pounds over the prior 6 months, current pregnancy or breast feeding, and concurrent participation in another clinical trial.
Recruitment and Entry
We recruited participants from the membership of Kaiser Permanente Northwest (KPNW), a non-profit health maintenance organization that provides comprehensive medical care to approximately 470,000 members in the Portland, Oregon metropolitan area. Two outreach strategies were implemented. First, we identified potentially eligible participants electronically from KPNW administrative databases, and mailed an invitation to participate. Second, we used a variety of media to publicize the study broadly among KPNW members and employees. These included emails to broad distribution lists of KPNW employees, postings in employee newsletters, articles in member-directed health and wellness publications, and announcements on the member web site.
Individuals interested in the study contacted recruiters via telephone, email, or secure web site. Those who were interested and potentially eligible were scheduled for an information session to learn more about the study. At the information session, the principal investigator provided a general overview of the study and answered questions. Those interested in being considered for enrollment scheduled an entry visit to determine final eligibility. Participants who met eligibility criteria at the entry visit and attended the first weight loss session (G1) were considered to be enrolled.
Weight Loss Intervention
The weight-loss intervention consisted of 22 group sessions led by nutrition and behavioral counselors, over six months. Specific intervention goals are listed in .
Intervention participant targets
The intervention approach, based on social cognitive theory, behavioral self-management techniques, trans-theoretical, or stages-of-change, models, and motivation enhancement(27
) was designed to be supportive, participant-centered and interactive. The intervention targets focused on weight loss. Each group (20–25 participants) met weekly for 90 minutes. Group leaders followed standardized session outlines. Each session began with a check-in focused on accomplishments and barriers with regard to each participant's individual weekly goals. Guided small-group activities followed the check-in and fostered problem-solving, social support and relapse prevention planning. Group activities included calorie awareness activities, record-keeping skill development, nutrition and physical activity demonstrations and goal-setting modules. At the end of each session, each participant developed a plan for the upcoming week by setting food and exercise goals, and a specific action plan for achieving each goal. Participants were provided with a weekly record-keeping diary and encouraged to track all foods consumed and all exercise completed. The intervention leaders reviewed the diaries each week and provided encouragement and support for keeping records. Participants were weighed at each group session.
Intervention Standardization, Training, and Quality Control
The group session curriculum was adapted from the first phase of the Weight Loss Maintenance Trial. Group leaders met together weekly to discuss the progress of each group and to assure the topics were covered in similar ways. To ensure that leaders conducted groups according to the session outlines, we used a system of random observations. Observers (lead interventionist, PI, co-investigators, and other outside experts) completed an observation checklist and discussed any findings with the group leader in a debrief session. The PI regularly reviewed the observation checklists.
At the entry visit, trained and certified staff measured participant height to the nearest 0.1cm using a calibrated, wall-mounted stadiometer. Staff measured weight at entry, at G1, at each weight loss session attended, and again at the post-weight loss intervention (PWL) visit approximately 6 months later. The latter visit was used to determine eligibility for randomization into Phase II. Weight was measured to the nearest ¼ pound by a high-quality digital scale with the participant in light indoor clothes without shoes. Weight was measured in pounds and converted to kilograms for analysis and reporting. The Bureau of Weights and Standards certified the scale annually, and study personnel assessed the calibration at least quarterly. Change in weight was calculated as weight at the PWL visit (conclusion of the weight loss program) minus weight at G1, so change less than 0 indicates weight loss.
The following measures were collected at the entry and PWL visits. The Insomnia Severity Index
) is a 5-item questionnaire measuring a participant's perception of his or her sleep quality in the previous two weeks. Scores range from zero to 28, with a higher score indicating worse sleep quality. Participants indicated sleep time
by selecting a response closest to their average amount of sleep in a typical 24-hour period. Response categories, in hours, were less than or equal to five, greater than five to six, greater than six to seven, greater than seven to eight, greater than eight to nine, and greater than nine.
Participants indicated screen time by selecting a response closest to their average amount of screen time per 24 hour period (computer use or television) during the previous 7 days, with separate values for work days and days off.
The Perceived Stress Scale
(PSS) is a ten-item questionnaire with scores ranging from zero to 40; higher scores indicate greater stress in the previous month.(33
The Personal Health Questionnaire
– Depression Subscale
(PHQ-8) is an eight item instrument with scores ranging from zero to 24;, higher score indicates greater depression symptoms during the previous 2 weeks.(35
In preparation for analysis, the data were audited and missing values were replaced using multiple imputation (data augmentation with Markov Chain Monte Carlo generation of imputed values, SAS PROC MI). The inclusive strategy recommended by Collins(36
) was used, with correlates of missing values as well as of missingness included in the MI model. Five copies of the imputed data were generated, followed by identical analyses across all copies and combination of results using Rubin's(37
As this is a two phase study, a main purpose of the PWL visit was to determine eligibility for the protocol's second phase. Participants who had fallen short of the 4.5kg weight loss requirement were less likely to show up for their PWL visit, and a total of 120 participants had weights imputed for this visit. However, because participant weights were recorded at each of the 22 group weight loss sessions attended, there were multiple weights documented across time for every participant, and the imputation thus calculated at extremely high efficiency (>99%)
We used a logistic regression model to evaluate whether sleep time, ISI score, and screen time at entry predict success in the weight loss program, where randomization into Phase II was the binary measure of success. Ordinal sleep and screen time measures were parameterized as orthogonal polynomials. Secondarily, PHQ-8 and PSS scores were added to the predictive model. In post hoc analysis, measures found to be not significant in the full model were stepped out. A multiple regression analysis with weight change (normally distributed) as the dependent variable examined the same predictors in the same series of steps.
Correlations between change in sleep time, insomnia, screen time, depression, and stress with weight loss were estimated, including graphical evaluation of potential non-linearity. Correlations were also estimated among adherence measures (session attendance, exercise minutes, food diaries) and between these and weight loss.
Power calculations projected a requirement of 288 participants for phase II of the project. Based upon experience from our prior studies, we targeted a total of 450 participants for phase 1, anticipating a 64% yield to phase II. Our final numbers showed 472 enrolled in phase I, with a 60% yield to phase II.