Adding an Activity Tracker to an Ongoing Community-Based Weight-Loss Program: Preliminary Results of an RCT Accepted sig younger than declined t(df)=-2.589(264);p=.01;. Greater proportion of AA in Experimental Group compared to Control Group χ2(df)=4.45(1);p=.035;η2=.092. Greater proportion of Hispanic in Control group and Greater proportion of Non-Hispanic in Experimental group, χ2(df)=4.87(1);p=.027; η2=.099. The difference in proportions of Caucasians in the Accepted and Declined groups approached significance, χ2(df)=3.155(1);p=.076;η2=.109. ITT analyses were used for weight-change analyses. Ind. Samples t-test between Accepted and Declined groups showed sig diff for Initial weight (t(df)=3.375(264);p<.001), change in weight (t(df)=-2.732(264);p=.007), and change in BMI (t(df)=-2.793(264);p=.006). Further, a greater proportion of the Accepted group lost 3% weight (χ2(df)=6.699(1);p=.010;η2=.159) Ind. Samples t-test b/t control and exp groups showed trend toward sig for N of account logins, t(df)=-1.840(413);p=.066. Ind. Samples t-test b/t accepted and declined groups showed sig diff for N of weigh-ins, t(df)=3.301(194.9);p<.001; % of emails opened, t(df)=3.170(168.8);p=.002; N of account logins, t(df)=3.234(151.0);p<.001; N of referrals to friends, t(df)=2.087(53.9);p=.042; and N of quizzes completed, t(df)=4.021(37.5);p<.001. 1,2Kathryn E. Wilson, 2Samantha M. Harden, 2Anna E. Taggart, 3Lia Schoepke, 3Todd McGuire, & 1,2Paul A. Estabrooks 1University of Nebraska Medical Center, Omaha, NE; 2Virginia Tech, Blacksburg, VA; 3IncentaHealth, Denver, CO Total WAW Online Registration During Recruitment Window n = 2,405 Total Randomized n = 525 Ineligible n = 1,070 BMI < 30 kg/m2 = 728 Male = 196 PA tracker already synced = 25 Postal Code = 121 Randomized Control Group n = 259 Randomized Experimental Group n = 266 Accepted PA Tracker n = 134 Synced PA Tracker n = 62 Did not weigh in n = 716 Not Contacted n = 94 Did not sync PA Tracker n = 72 WAW Enrollment/ Recruitment Pool n = 1,689 Declined PA Tracker n = 132 Active = 2 Passive = 130 Declined Offer; Ind. PA Tracker Sync n = 7 Ind. PA Tracker Sync n = 22 Table 2. Baseline values and weight-loss outcomes according to group.   Control Experimental Total Accepted Declined M(sd) Initial Weight (kg) 222.9(40.5) 222.3(40.9) 230.7(41.3) 214.0(38.9)** Initial BMI (kg/m2) 37.8(6.4) 37.4(6.1) 37.9(6.2) 36.9(6.0) Weight-loss (kg) -3.5(8.1) -3.3(8.5) -4.7(10.1) -1.9(6.0)* Change in BMI -.59(1.4) -.83(1.7) -.34(1.0)* N(%) Achieved 3% weight-loss 44(17.0) 51(19.2) 34(25.4) 17(12.9)* Achieved 5% weight-loss 29(11.2) 32(12.0) 20(14.9) 12(9.1) *p<.01; **p<.001. Negative means reflect a reduction in weight and BMI. Background & Purpose Background: Many web- and community-based weight-loss programs include the opportunity for participants to synchronize commercially available physical activity (PA) trackers, but the degree to which the provision of such a device would improve participant engagement and weight loss is unclear. Purpose: The purpose of this study was to determine the reach and effectiveness of offering a PA tracker to program participants with the goal of improving program engagement and weight-loss outcomes. Methods A sample of 525 obese (37+6.2 kg/m2) females (44+12.6 yrs) newly enrolled in a web- and community-based weight-loss program were randomized into either an experimental or control group. The experimental group was offered a free PA tracker and asked to provide size and color preferences. Devices were sent to experimental participants who accepted the offer. Program engagement, device use, and weight (lbs) were tracked for three months after program enrollment. Table 3. Engagement outcomes according to group.   Control Experimental Total Accepted Declined M(sd) N of Weigh-ins 3.4(5.8) 3.4(4.5) 4.3(5.6) 2.5(2.8)*** % of Emails opened 26.2(31.8) 29.5(34.1) 36.3(36.4) 20.5(28.7)** N of Account logins 9.8(18.1) 15.2(37.5)† 21.8(47.2) 6.9(15.9)*** N of Facebook posts 6.8(3.4) 16.6(25.6) 0(0) N of Journal entries 2.8(3.1) 4.0(5.5) 4.4(6.1) 2.9(3.1) N of Referrals to friends 2.5(2.6) 2.4(2.1) 2.7(2.4) 1.7(1.1)* N of Online quizzes completed 9.4(14.5) 11.2(12.0) 13.8(13.1) 4.0(2.8)*** Average quiz score 84.8(21.3) 81.7(20.7) 81.3(20.2) 82.8(23.0) †p<.10; *p<.05; **p<.01; ***p<.001. Results Of the 266 participants in the experimental sample, 50% accepted the offer, and 23% synced the device to the program. Nine percent of the control participants independently obtained and synced a PA tracker. At 3-months, the experimental group showed greater program engagement than the control group, but only in use of online journal entries (OR(95%CI)=2.08(1.29,3.37)). There were no significant differences in weight-loss outcomes. Those who accepted the device weighed more at baseline (t(df)= 3.4(264); p=.001), and lost more weight (t(df)=-2.73(264); p=.007) than those who did not accept the offer, and they were more likely to lose 3% body weight (OR;95%CI=2.3;1.21,4.37) and less likely to drop-out (OR;95%CI=2.6; 1.58,4.28). Table 1. Demographic descriptions for participants according to group.   Control Experimental Total Accepted Declined N 259 266 134 132 M(sd) Age, yrs 43.3(12.6) 44.4(12.5) 42.4(11.3) 46.4(13.4)** N(%) Ethnicity  Hispanic 75(29.0) 56(21.1)* 25(18.7) 31(23.5) Non-Hispanic 167(64.5) 196(73.7)* 105(78.4) 91(68.9) Refuse to answer 17(6.6) 14(5.3) 4(3.0) 10(7.6) Race  African American 18(6.9) 33(12.4)* 16(11.9) 17(12.9) Asian 1(.4) 1(.7) 0(0) Caucasian 178(68.7) 177(66.5) 96(71.6) 81(61.4)† Native American 5(1.9) 6(2.3) 3(2.2) 3(2.3) Other 37(14.3) 37(13.9) 14(10.4) 23(17.4) 20(7.7) 12(4.5) 8(6.1) †p<.10; *p<.05; **p<.01. Conclusions Offering a free PA tracker for use in a web- and community-based weight-loss program reaches a greater proportion of the sample than would independently use this feature. However, this does not translate into improved weight-loss. Data collected at 6 and 12 months will be used to determine longer-term effectiveness. Acknowledgements Thanks to the Fralin Translational Obesity Research Center and IncentaHealth for providing funding to conduct the study.