Introduction

Overweight and obesity in the U.S. population have reached epidemic proportions, with about 66% of U.S. adults being overweight or obese (1). The dramatic increase in prevalence of obesity over the past two decades cannot be explained by genetic changes, but by environmental factors that encourage increased energy intake and decreased energy expenditure (2). Environmental, community, and societal factors influence dietary and physical activity behaviors and may foster a positive energy balance (2, 3), suggesting that strategies for addressing the obesity epidemic must include environmental approaches.

Environmental approaches use policies, programs, or organizational practices to influence behaviors by, for example, increasing the availability of, and providing access to, healthful food choices and facilities for physical activity, and by creating a socially supportive environment. Such approaches do not require individuals to self-select to defined educational programs (4). Worksites are viable settings for reaching large numbers of working adults of varying socioeconomic levels and ethnic backgrounds. A key hypothesis for research is that interventions to promote behavior change in such settings could be generalizable, cost-effective, and sustainable. If proven effective and widely implemented, environmental interventions could have a major impact on the health of employees and, thus, on the health of the nation, as well as provide a positive return on corporate investments.

In September 2004, the National Heart, Lung, and Blood Institute (NHLBI)¹ funded seven institutions to collaborate with worksites across the country to test interventions emphasizing environmental approaches to behavior change for overweight and obesity control. These institutions are Cornell University, Washington, DC; Kaiser Permanente, Honolulu, HI; Tulane University, New Orleans, LA; the University of Massachusetts Medical School, Worcester, MA; the University of Minnesota, Minneapolis, MN; the University of Rochester, Rochester, NY; and the University of Washington, Seattle, WA. Each study is conducted independently under the direction of a local principal investigator. Unlike multi-site clinical trials, these studies are being conducted in different types of worksites (e.g., hotels, hospitals, and businesses) that have diverse employee populations.

The purpose of this paper is to describe these NHLBI-supported studies, focusing on their design characteristics, interventions, common measures, and study collaboration. These are innovative studies that emphasize environmental strategies to change or modify behaviors related to diet and physical activity for weight control and obesity prevention at worksites as well as examine the economic benefits of such strategies. Information on the design, implementation, and evaluation of worksite obesity management programs could be useful to researchers designing such programs. Also, if found effective, such studies could lead to policies and practices that enhance employee health and contribute to the financial well being and reduced healthcare needs of employees and employers.

Obesity prevention at various settings, including worksites, emerged as a priority during NHLBI strategic planning meetings held in 2000 and 2002. Documents supporting worksite intervention studies include the Healthy People 2010 Objectives (5) and the Surgeon General's Call for Action (6). A review of published worksite intervention studies for overweight and obesity control indicated that most interventions focused on individual-directed approaches of minimal intensity and short-term duration (6 months or less). Some had modest but significant intervention effects on weight after 6 months (7, 8). Studies that addressed environmental influences or psychosocial factors as mediators or moderators of weight control were rare (8). Most of the studies were conducted in large worksites (>500 employees) with few racial and ethnic minorities, and a limited number had worksites as units of randomization and analysis. The theoretical bases of the interventions and studies on cost-effectiveness or benefits were rarely reported (8). These gaps suggest a need to determine the effects of environmental interventions on weight and weight-related outcomes. Toward this goal, the NHLBI supported seven independent studies for a two-phase, four-year program. Phase I activities include formative assessment using methods such as focus groups, interviews with employees and administrators, surveys, assessments of the worksite environment and pilot testing of intervention components. Phase II includes a two-year intervention study to test innovative strategies that have strong theoretical underpinnings, seem to be practical, cost-effective, and sustainable without incurring undue costs, and are being refined based on Phase 1 activities and results.

Research Methods and Procedures

Design Characteristics

Table 1 presents the design characteristics of the seven funded studies. Across the seven studies, there is a total of 114 worksites (range, 4 to 30 per study site) with about 48,000 employees (range 1200 to 10,600 per study site), mostly low- to middle-income and from diverse racial and ethnic groups. A total of about 23,000 employees are randomly selected for measurement. Worksites are units of randomization in all of the studies; they are randomly assigned to intervention or comparison groups, with prior pair matching used in three studies. In all of the studies, the inclusion criteria consist of stable worksites (i.e., low turnover rates) whose administrators agree to 1) have worksites randomly assigned to intervention or comparison groups, 2) allow assessment of consenting employees at various time-points within the worksite, 3) provide space or support for intervention targeting the employees, and 4) encourage employee participation. All assessments are being conducted on work time or directly before or after shift changes and on site. Worksites provide time off for measurement. Each study was approved by a local Institutional Review Board and has a data and safety monitoring plan as well as Data and Safety Monitoring Board or other safety monitoring entity.

Table 1. - Characteristics of the national worksite overweight and obesity control studies.

Full table

Intervention

All of the studies use conceptual frameworks for their interventions (Table 1), including the socio-ecological framework that combined theoretical views of the environmental, individual, social, cultural, and policy factors that influence behaviors (9). One study uses an integrative model of worksite health promotion that emphasizes organizational and work environmental factors (10). This model, which is based on a systems perspective, argues that workplace health promotion efforts must address 1) organizational factors (e.g., socio-cultural, economic), 2) the work environment (e.g., physical and structural), and 3) job demands and worker characteristics. Thus, the intervention targets job demands and worker characteristics, physical work environment, and the socio-organizational environment. For example, in some worksites, specific job requirements or conditions limit or facilitate opportunities for physical movement. Thus, weight management strategies address these job demands in such worksites. Another study uses a framework that posits that the obesity epidemic can best be controlled by targeting the epidemiological triad: hosts, vectors of agents, and environments (11). The study targets the employee (or host), energy intake and output (or vectors of the agent, positive energy balance, for example, energy dense foods, large portion sizes and physical inactivity), and the obesogenic environment (11).

Formative research (Phase I) is being used to refine, modify, enhance, or develop the intervention strategies. The studies are using combinations of intervention strategies that have been shown to be successful in the literature (e.g., vending machines) or were pilot-tested in Phase I. Further, the studies employ employee advisory boards whose members suggest additional interventions or modifications to planned interventions and serve as program champions/advisors to help implement the intervention. Also, process evaluation data (e.g., number of people who used pedometers, weighed themselves daily, take the stairs, or read study-specific newsletters) are collected and are being used to improve the intervention (12). Table 2 presents examples of environmental strategies addressing diet and physical activity, and promotional activities used by the studies. The environmental intervention strategies include portion size reduction and recipe modifications of cafeteria foods, preferential pricing for healthful foods in vending machines, and provision of fitness equipment. Individual-level interventions are also included, for example, group or individual weight loss management programs for highly motivated employees with BMI >30 (Work, Weight and Wellness Program, Kaiser Permanente, Hawaii) or group-level educational programs are being offered to all employees (Step Ahead Program, Massachusetts; and the Lighten-Up Program, Cornell). All interventions are about two years in duration (Table 1).

Table 2. - Examples of promotional activities and strategies of environmental intervention for physical activity and diet.

Full table

Measurements

Table 3 presents a list of tools and instruments that are being used by the studies. These include weight scales for body weight/BMI, the Godin survey for assessing physical activity, fast foods and fruit and vegetable consumption questionnaire, the Work Limitations Questionnaire, short form, to measure worker productivity, and a healthcare use and absenteeism survey. The primary outcome measure for all studies is change in BMI or body weight. Secondary measures include waist circumference, individual dietary intake, objective measures of physical activity (e.g., accelerometry), self-reported measures of physical activity (e.g., questionnaires assessing free-time physical activity), work productivity, healthcare use, and cost benefit (e.g., return on investment and programmatic and medical costs). Study-specific measures include blood pressure, depressive symptoms, social support, tobacco and alcohol use, and self-report measures of sleep. Lack of sleep has been positively correlated with obesity and could mediate intervention effects on body weight (13, 14).

Table 3. - List of measures by worksite program.

Full table

Dietary intake is being assessed by 24-hour recalls (2 weekdays and 1 weekend) conducted by three studies. Common questionnaires are being used to assess patterns of intake of specific foods such as fast foods, soft drinks, and fruits and vegetables. Such foods correlate significantly with body weight or healthful eating (15, 16, 17, 18, 19). Environmental measures of diet and physical activity are assessed using a modified version of the Checklist of Health Promotion at Worksites (20), which has been found to have reliability coefficients ranging from 0.8 to 1.0.

Physical activities of participants are assessed by the Godin leisure-time physical activity questionnaire, which typically has moderate-to-high reliabilities for assessing light, moderate, and strenuous physical activity. The Godin questionnaire has Cronbach's ranging between 0.62 and 0.74 (21). For all of the studies, the Godin questionnaire was modified for clarity by listing the intensity of physical activity for days per week, and minutes of activity in 10- to 15-minute increments, from 0 minutes to 60 minutes. Four studies use accelerometers to provide objective measures of physical activity. Physical activity thresholds and imputation methods are defined by the methods proposed by Treuth et al. (22) and Catellier et al. (23).

Questions from the International Physical Activity Questionnaire (24) that focus on job-related physical activity are being used by five of the studies. The International Physical Activity Questionnaire has been tested in 12 countries and found to have acceptable measurement properties for use in many settings, including worksites. It has a moderate-to-high test-retest reliability coefficient of 0.8.

All of the studies use the Work Limitations Questionnaire to assess work productivity (25). The short, 8-item version of the Work Limitations Questionnaire is used to measure the degree to which health problems interfere with ability to perform job roles. It assesses employees' perceived health problems, such as physical, mental, and interpersonal demands, and how these problems interfere with specific aspects of job performance (on-the-job disability) (25). Cronbach's statistics are typically between 0.7 and 0.9.

Employees who have been randomly selected to be measured complete the healthcare use questionnaire, which assesses sick days and doctor's visits and has been examined for face validity (26). The studies assess cost benefit by calculating the return on investment, which can be defined either as net present value (i.e., the ratio of inflation-adjusted discounted savings to program expenses), or as the benefit-to-cost ratio (27, 28). All sites collect data on healthcare use, absenteeism, and presenteeism to estimate program savings. Data are monetized and savings are compared with program expenses to calculate return on investment (27).

Other study-specific assessments (two studies) include the effects of sleep duration on body weight. The Sleep Symptoms Questionnaire has good internal consistency reliabilities, with Cronbach's coefficients ranging from 0.91 to 0.98 (13).

In addition to the outcome measures, each study uses process measures to examine intervention dose, fidelity, and reach (12). Examples include number of promotional activities (dose), intervention staff's delivery of intervention according to established protocol (fidelity), and participation in worksite food and physical activity contests (e.g., percent attending compared with that expected) (reach).

Although the investigators focus on different populations, use diverse intervention strategies, and address their own specific research questions, the studies have similar primary and secondary outcome measures (Table 3) and similar designs, which encourage common statistical analytical approaches. Selected data from two or more studies would be pooled for secondary analyses to obtain greater statistical power or to examine age, gender, or racial differences. This collaborative process has the potential to enhance comparability of results and create a synergy of creative expertise of investigators to address the obesity problem through worksite environmental intervention strategies. Despite these benefits, there are challenges in this procedure. For example, all sites must adhere to similar procedures in data collection and must develop common analytical plans to establish comparability and generalization of the results. However, successful results from two or more worksites have the potential to be translated to other businesses.

Study Collaboration and Monitoring

The Center for Health Research of Kaiser Permanente, Northwest, serves as the coordinating center for the seven projects. It facilitates communication, cooperation and scientific collaboration among the seven projects. To accomplish study objectives, the NHLBI established a steering committee for the overall research program to facilitate communication among the scientists and staffs. The overall leadership of the research program is the responsibility of the steering committee consisting of the principal investigators of each study and the NHLBI Project Scientist. The coordinating center maintains a program Web site, which allows secure access to study protocols, procedures for data collection, assessment tools, and secure transfer and sharing of data among investigators to facilitate across-site data analyses.

In summary, the worksite intervention studies program is a unique collaborative program among seven studies with the common aim of testing the effectiveness of worksite environmental strategies to control overweight and obesity in adults.

The findings from the studies could be useful to researchers and employers because they could provide guidance for designing, implementing, and evaluating worksite obesity interventions, and for making such interventions an integral part of employee health promotion. Interventions found to be cost-effective and implemented in the worksite setting have the potential to improve health and reduce medical care costs for employers, and could motivate others to implement such programs within their worksites. Data pooled from these studies could enhance the translation to, and data sharing with, other worksites. Findings from this program of studies have the potential to guide other worksite obesity interventions and influence worksite policies for overweight and obesity control. The studies could also provide qualitative data on how to secure management support and organizational commitment to conduct scientific research in business settings, and methods to encourage participation of employees.

The emphasis on environmental strategies (or a combination of environmental and individual strategies) and the focus on large-scale changes in dietary and physical activity behaviors are promising approaches to improve dietary and physical activity behaviors, thereby curtailing the obesity epidemic (29, 30).

Notes

¹ Nonstandard abbreviation: NHLBI, National Heart, Lung, and Blood Institute.

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Acknowledgments

The authors thank Ronald J. Ozminkowski, (Health and Productivity Research, Thomson Medstat); Peter Kaufmann, Eva Obarzanek, and Denise Simons-Morton (NHLBI) for reviewing the manuscript; and Judy L. Donald (Kaiser Permanente, Northwest) for coordinating the study. This study was supported by NHLBI Grants R01 HL79478, R01 HL79483, R01 HL79491, R01 HL79505, R01 HL79509, R01 HL79511, and R01 HL79546.