Physical activity and dietary behavior change in Internet-based weight loss interventions: comparing two multiple-behavior change indices.

OBJECTIVE: To investigate the effects of two Internet-based weight loss interventions on physical activity (PA) and dietary behaviors using two approaches for computing combined behavior change. METHOD: Participants were 352 overweight/obese women and men completing 12-month interventions in San Diego, California during 2002-2007. Moderate-to-vigorous PA (MVPA) and sedentary time were measured with accelerometers, and dietary fat and fruit and vegetable intake were assessed with food frequency questionnaires. Longitudinal analyses tested the effect of the intervention on combined health behavior change quantified using a standardized residualized change index (SRCI) and a risk factor change index (RFCI). RESULTS: At baseline, participants engaged in an average of 153 min/week of MVPA and 525 min/day of sedentary time, and consumed 37% of calories from fat and <3 fruits and vegetables per day. The interventions had a significant effect on combined behavior change as measured with each approach (p<0.001). The intervention effect was larger (p<0.001) when evaluated using the SRCI (standardized regression coefficient [Beta]=0.30) than the RFCI (ß=-0.18). CONCLUSION: Interventions that target both PA and dietary behaviors appear effective. The SRCI was more sensitive for evaluating the intervention, but the RFCI may be easier to use for communicating public health significance.

Effects of Behavioral Contingencies on Adolescent Active Videogame Play and Overall Activity: A Randomized Trial.

OBJECTIVE: This study evaluated the effect of four active videogames (AVGs) varying in behavioral contingencies (behavior-consequence relations) on adolescent AVG play and overall activity levels over 4 weeks. MATERIALS AND METHODS: Each AVG, manufactured by SSD/Xavix(®) (Shiseido Co. of Japan, Tokyo, Japan), was coded and scored for the number of positive and aversive behavioral contingencies within the games. "Bowling" and "Tennis" were classified as having "higher contingency scores," and "Boxing" and aerobic fitness training were classified as having "lower contingency scores." Adolescents (n=63; 11-15 years old; 62% male; 38% Hispanic; 44% overweight or obese) were randomized to play one of the four AVGs at home and recorded game play sessions in a paper log. Baseline and week 4 assessments were completed at home; week 1, 2, and 3 assessments were completed by telephone. Accelerometers were worn during baseline and weeks 1 and 4. RESULTS: Accelerometer-measured sedentary and light activity hours/day were stable over time, whereas moderate-vigorous physical activity minutes/day increased in the higher contingency group and decreased in the lower contingency group (interaction effect, 6.43, P=0.024). Reported game play minutes decreased in both groups from week 1 to week 4 (-29.42 minutes, P=0.001). DISCUSSION: There was some support for the hypothesis that AVGs with more behavioral contingencies, compared with AVGs with fewer behavioral contingencies, result in more physical activity. However, overall AVG play decreased substantially after the first week. Further study is needed to better understand how behavioral contingencies can be used in AVGs to enhance their potential to provide health benefits to game players.

Adolescent screen time and rules to limit screen time in the home.

PURPOSE: To investigate associations between adolescent screen time behaviors, screen time rules, and presence of electronic media in the bedrooms of adolescents. METHODS: Parents and adolescents (N = 160 dyads) from the cities of Boston, Cincinnati, and San Diego were asked to complete a questionnaire which included questions related to demographics, screen time rules, availability of media devices, and screen time behavior. Separate multiple regression models were used for adolescent and parent reports to test correlates of adolescent television (TV) watching, video game play, and computer usage for entertainment. RESULTS: Data from adolescents indicated that rules for watching TV, computer usage, and total number of screen time rules were significantly correlated with time spent watching TV (ß = -.22, p < .01), playing video or computer games (ß = -.18, p < .05), and using the Internet and/or computer for entertainment (ß = -.18, p < .05), respectively. Data from parents indicated that TV rules were significantly associated with lower rates of TV viewing, and parent-adolescent agreement on rules strengthened this relationship. Data from parents as well as adolescents indicated that the presence of a TV in the bedroom was positively associated with TV viewing time (ß = .18 and .24, p < .05, respectively). Adolescent data indicated a positive association between having at least one video game system in the bedroom and time spent playing video games (ß = .19, p < .05). CONCLUSION: Having clear rules, setting limits on screen time, and not having screen-based media in the bedroom were associated with fewer hours of screen time for adolescents.