Physical Activity and Sedentary Behavior Change; Impact on Lifestyle

Translation efforts based upon the successful Diabetes Prevention Program (DPP) have shown that this behavioral lifestyle intervention model is effective in a variety of diverse community settings. Despite the fact that physical activity is a key part of the DPP lifestyle intervention as one of the two intervention goals, activity change in the DPP, and/or the resulting translation studies modeled after it, has not been adequately verified with an accurate objective measure. In addition, previous research has shown that, in many subgroups of the general population, moderate and vigorous physical activity is non-existent. Individuals with activity only at the low end of the intensity spectrum may have a difficult time increasing their levels of moderate+ intensity physical activity for various reasons such as limited function or lack of motivation. For these individuals, interventions with a movement goal of increasing planned bouts of moderate intensity activity may not be as effective and therefore not as beneficial as interventions with a movement goal of decreasing time spent sitting.

The purpose of this proposal is to understand the impact of movement, specifically physical activity and sitting time, in a DPP-adapted community lifestyle intervention, Group Lifestyle Balance (GLB).

Aim 1: To determine if the GLB lifestyle intervention, shown to be effective in translation efforts in decreasing weight and increasing self-reported activity, has significant changes in physical activity levels determined by a validated objective measure, the accelerometer. It is hypothesized that participants randomized to the conventional lifestyle intervention arm (GLB-MOD) will have significant improvements in our primary endpoints of weight and physical activity (measured objectively) compared to a delayed-intervention control at 6 months and will have reductions in several secondary outcome measures (fasting glucose, insulin, blood pressure, waist, lipids, physical function, and quality of life).

Aim 2: To determine if a lifestyle intervention program similar to the one described above, with the only change being that the activity focus is now replaced with an inactivity focus (GLB-SED), is also effective. It is hypothesized that participants randomized to GLB-SED will have a significant improvement in the primary endpoints of weight and decreased inactivity (measured objectively) compared to a delayed-intervention control at 6 months and will have significant reductions in several of the secondary endpoints (fasting glucose, insulin, blood pressure, waist circumference, lipids, physical function, quality of life).

Secondary Aims: To examine the pre-post change in participants for weight, physical activity (objective and subjective), and sedentary time from baseline to 6 and 12 months of intervention for each randomized arm and to understand the inter-relationships of these behavioral factors over time. It is hypothesized that those GLB-MOD participants who achieve significant weight loss will also have significant increases in their moderate+ intensity activity levels. Similarly, we hypothesize those GLB-SED participants who achieve significant weight loss will also have significant decreases in the amount of time they spent sedentary/sitting. An estimate of the difference in participant cost between the two versions of the lifestyle intervention programs will also be determined.

Aim #1 addresses an important remaining gap in the prevention literature; does objectively measured activity improve as a result of the existing intervention that is being used in DPP-based translation efforts and does this change in activity have an impact on weight change? Aim #2 examines the impact of replacing the conventional physical activity goal of increasing planned and relatively brief bouts of moderate physical activity with one focusing on decreasing sedentary time within the framework of a successful translation lifestyle intervention adapted from the DPP, the Group Lifestyle Balance (GLB) program.

The study design is a prospective, six month delayed-control intervention in which 321 subjects (age 50 and older with a BMI of ≥24 kg/m2 and with prediabetes and/or metabolic syndrome) will be recruited from community centers and randomly assigned to one of three groups: the standard GLB program which includes the conventional moderate activity goal (GLB-MOD), the GLB program with a focus on decreasing sedentary behavior (GLB-SED), or delayed intervention. Subjects assigned to GLB-MOD and GLB-SED will each, separately be compared at 6 months to the delayed-control group after which time, the delayed group will be randomly assigned to either GLB-MOD or GLB-SED. Participants will complete baseline, 6, and 12 month assessment visits. Change in weight, objectively measured activity, and time spent sedentary are the primary outcomes with secondary outcomes including change in self-reported physical activity, HbA1c, fasting glucose, lipids, blood pressure, waist circumference, quality of life and physical function.

It is hypothesized that physical activity assessed by accelerometry in GLB-MOD will significantly increase (mostly moderate intense activity) and that there will be a significant decrease in weight, which will partly be related to change in activity levels. The 2nd hypothesis is that the GLB-SED intervention will significantly decrease time spent sitting as measured by accelerometry and that this change will also be related to a significant decrease in weight. The information that will be gained from this entire effort is important, innovative, and will allow us to obtain a complete and accurate understanding of both ends of the physical activity/inactivity spectrum and their impact in community prevention intervention programs. If shown to be effective, the innovative, modified sedentary-focused translation intervention program would provide a valuable future translation option.