***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Schools are the most frequent target for intervention programs aim ed at preventing child obesity ; however , the overall effectiveness of these programs has been limited . It has therefore been recommended that interventions target multiple ecological levels ( community , family , school and individual ) to have greater success in changing risk behaviors for obesity . This study examined the immediate and short-term , sustained effects of the Switch program , which targeted three behaviors ( decreasing children 's screen time , increasing fruit and vegetable consumption , and increasing physical activity ) at three ecological levels ( the family , school , and community ) . Methods Participants were 1,323 children and their parents from 10 schools in two states . Schools were matched and r and omly assigned to treatment and control . Measures of the key behaviors and body mass index were collected at baseline , immediately post-intervention , and 6 months post-intervention . Results The effect sizes of the differences between treatment and control groups ranged between small ( Cohen 's d = 0.15 for body mass index at 6 months post-intervention ) to large ( 1.38 ; parent report of screen time at 6 months post-intervention ) , controlling for baseline levels . There was a significant difference in parent-reported screen time at post-intervention in the experimental group , and this effect was maintained at 6 months post-intervention ( a difference of about 2 hours/week ) . The experimental group also showed a significant increase in parent-reported fruit and vegetable consumption while child-reported fruit and vegetable consumption was marginally significant . At the 6-month follow-up , parent-reported screen time was significantly lower , and parent and child-reported fruit and vegetable consumption was significantly increased . There were no significant effects on pedometer measures of physical activity or body mass index in the experimental group . The intervention effects were moderated by child sex ( for fruit and vegetable consumption , physical activity , and weight status ) , family involvement ( for fruit and vegetable consumption ) , and child body mass index ( for screen time ) . The perception of change among the experimental group was generally positive with 23 % to 62 % indicating positive changes in behaviors . Conclusion The results indicate that the Switch program yielded small-to-modest treatment effects for promoting children 's fruit and vegetable consumption and minimizing screen time . The Switch program offers promise for use in youth obesity prevention BACKGROUND Price can influence food purchases , which can influence consumption . Limited laboratory research has assessed the effect of price changes on food purchases , and no research on individual differences that may interact with price to influence purchases exists . OBJECTIVE We aim ed to assess the influence of price changes of low-energy-density ( LED ) and high-energy-density ( HED ) foods on mother 's food purchases in a laboratory food-purchasing analogue . DESIGN Mothers were r and omly assigned to price conditions in which the price of either LED or HED foods was manipulated from 75 % to 125 % of the reference purchase price , whereas the price of the alternative foods was kept at the reference value .  Mothers completed purchases for 2 income levels ( $ 15 or $ 30 per family member ) . RESULTS Purchases were reduced when prices of LED ( P < 0.01 ) and HED ( P < 0.001 ) foods were increased .  Maternal BMI  interacted with price to influence purchases of HED foods when the price of  HED  foods increased ( P = 0.016 ) and interacted with price to influence purchases of LED foods when the price of HED foods increased ( P = 0.008 ) . CONCLUSION These results show the relevance of considering price change as a way to influence food purchases of LED compared with HED foods and the possibility that individual differences may influence the own-price elasticity of HED foods and substitution of LED for HED foods OBJECTIVES This study examined the effects of pricing and promotion strategies on purchases of low-fat snacks from vending machines . METHODS  Low-fat snacks were added to 55 vending machines in a convenience sample of 12 secondary schools and 12 worksites . Four pricing levels ( equal price , 10 % reduction , 25 % reduction , 50 % reduction ) and 3 promotional conditions ( none , low-fat label , low-fat label plus promotional sign ) were crossed in a Latin square design . Sales of low-fat vending snacks were measured continuously for the 12-month intervention . RESULTS Price reductions of 10 % , 25 % , and 50 % on low-fat snacks were associated with significant increases in low-fat snack sales ; percentages of low-fat snack sales increased by 9 % , 39 % , and 93 % , respectively . Promotional signage was independently but weakly associated with increases in low-fat snack sales . Average profits per machine were not affected by the vending interventions . CONCLUSIONS Reducing relative prices on low-fat snacks was effective in promoting lower-fat snack purchases from vending machines in both adult and adolescent population This study reports the effect of a  school-r and omized fruit and vegetable intervention consisting of a subscription to the Norwegian School Fruit Programme at no parental cost , and the Fruit and Vegetables Make the Marks ( FVMM ) educational programme , both delivered in the school year of 2001 - 02 . Nine r and omly chosen schools received the intervention and 10 schools served as control schools . Participating pupils completed question naires at baseline ( September 2001 ) , at Follow-up 1 ( May-June 2002 ) and at Follow-up 2 ( May 2003 ) . A total of 517 pupils ( 84 % ; mean age , 11.3 years at baseline ) participated in all three surveys . At both Follow-up 1 and Follow-up 2 , strong intervention effects were observed for all-day fruit and vegetable intake ( effect sizes were 0.6 and 0.5 portions , respectively ) . The sustained effect at Follow-up 2 , 1 year after the end of the intervention , can partly be explained by greater participation rates in the School Fruit Programme ( st and ard paid subscription ) . We conclude that the effects observed are most likely due to the no-cost subscription and not due to the FVMM educational programme , and that providing pupils with a piece of fruit or a vegetable at school at no cost for the parents is an effective strategy to increase  school children 's intake of fruit and vegetables . The effect is also sustained 1 year after the end of the no-cost subscription , providing increased health benefits Background / Objectives : Previous research in the United Kingdom , where there is a school canteen system , has shown that the Food Dudes intervention substantially increases children 's fruit and vegetable consumption . The current study evaluated its effectiveness in Irel and where school meals are not provided and children bring food to school in lunchboxes . Subjects/ Methods : Participants were 4- to 11-year-old children attending two primary schools ; the schools were r and omly assigned to experimental or control conditions ( n=228 and 207 , respectively ) . During the 16-day intervention in the experimental school , children watched video adventures featuring the heroic Food Dudes , and received small rewards for eating fruit and vegetables provided . In both schools , parental provision and children 's consumption of fruit and vegetables in the lunchboxes were assessed at baseline and 12-month follow-up ( Lunchbox measures ) . Fruit and vegetables were provided in both schools over an 8-day baseline phase and the 16-day intervention , and children 's consumption was measured ( school-provided food measures ) . Results : Relative to baseline , consumption of the school-provided foods increased during the intervention in the experimental school ( P<0.001 ) , whereas in the control school it showed a significant decline . At 12-month follow-up , parents in the experimental school provided and their children consumed significantly more lunchbox fruit , vegetables and juice relative to baseline and to the control school ( P<0.001 in all instances ) . Conclusions : The Food Dudes intervention was effective in changing parental provision and children 's consumption of lunchbox fruit and vegetables in Irel and BACKGROUND Our objective was to evaluate the effects of environmental , policy , and social marketing interventions on physical activity and fat intake of middle school students on campus . DESIGN Twenty-four middle schools were r and omly assigned to intervention or control conditions . Baseline measures were collected in spring 1997 , and interventions were conducted during the 1997 - 1998 and 1998 - 1999 school years SETTING /PARTICIPATION : The schools had mean enrollments of 1109 , with 44.5 % nonwhite students . Over 2 years , physical activity interventions were design ed to increase physical activity in physical education classes and throughout the school day . Nutrition interventions were design ed to provide and market low-fat foods at all school food sources , including cafeteria breakfasts and lunches , a la carte sources , school stores , and bag lunches . School staff and students were engaged in policy change efforts , but there was no classroom health education . MAIN OUTCOMES MEASURES Primary outcomes were measured by direct observation and existing records . RESULTS R and omized regression models ( N = 24 schools ) revealed a significant intervention effect for physical activity for the total group ( p < 0.009 ) and boys ( p < 0.001 ) , but not girls ( p < 0.40 ) . The intervention was not effective for total fat ( p < 0.91 ) or saturated fat ( p < 0.79 ) . Survey data indicated that the interventions reduced reported body mass index for boys ( p < 0.05 ) . CONCLUSIONS Environmental and policy interventions were effective in increasing physical activity at school among boys but not girls . The interventions were not effective in reducing fat intake at school . School environmental and policy interventions have the potential to improve health behavior of the student population , but barriers to full implementation need to be better understood and overcome OBJECTIVE To assess dietary costs during a  family-based pediatric obesity intervention . DESIGN Families were r and omized to one of two groups . Dietary and cost data were collected from a parent or child using three 24-hour recalls : at baseline , 6 months , and 12 months . SUBJECTS Thirty-one families with an obese 8- to 12-year-old child entered treatment , with complete dietary data provided from 20 families . INTERVENTION The 20-week behavior modification intervention emphasized increasing diet nutrient-density . Families attended group and individual sessions or group sessions . MAIN OUTCOME MEASURES Energy intake ; percent of energy from protein , fat , and carbohydrate ; servings and percent servings from food groups classified by nutrient density ; and daily food costs . STATISTICAL ANALYSES PERFORMED Mixed analyses of variance , with group as the between-subject factor , and time as the within-subject factor . RESULTS No significant effect of group was found in any analyses . Significant decreases in percent overweight were observed at 6 and 12 months for children ( -10.0+/-8.7 and -8.0+/-10.3 , respectively ) ( mean+/-st and ard deviation ) and parents ( -6.7+/-10.3 and -5.3+/-14.1 ) . Energy intake for parents and children combined significantly decreased from baseline ( 1,881+/-462 ) to 6 months ( 1,412+/-284 ) , and 1 year ( 1,338+/-444 ) . Servings from low-nutrient-dense foods significantly decreased from baseline ( 34.7+/-16.2 ) to 6 months ( 16.0+/-8.6 ) and 1 year ( 18.6+/-9.2 ) , causing a significant increase in diet nutrient density . Dietary cost did not change at 6 months , but significantly decreased from baseline to 1 year ( $ 6.77+/-2.41 to $ 5.04+/-1.80 ) . Cost per 1,000 kcal did not significantly change . APPLICATIONS/ CONCLUSIONS Adopting a lower-energy , nutrient-dense diet did not increase dietary costs over time . Consequently , cost should not be a barrier in the adoption of a healthful diet This study examines the feasibility and effectiveness of an environmental intervention for improving diet by comparing the impact of health messages , lowered prices , and their combination on the purchase of healthy food items in a restaurant . Price decreases alone , rather than a combination of price decreases and health messages , were associated with a higher level of increased purchases of some healthy food items as compared with control items over a 4-month period . Price decreases may be a more powerful means than health messages of increasing consumption of healthy foods . Health messages may have paradoxical effects if foods labeled as healthy are assumed to taste bad OBJECTIVE The objective of this study was to identify factors that predict offering and sale of competitive foods , as well as factors that predict average daily participation in school lunch . DESIGN Surveys were distributed to 271 school foodservice directors in a r and om sample of high schools in Pennsylvania that were selected to be representative of the entire population of high schools in Pennsylvania based on chosen demographic characteristics . SUBJECTS Two hundred twenty-eight school foodservice directors ( 84 % ) returned surveys . STATISTICAL ANALYSES Descriptive and multiple regression analyses were done using SPSS version 11.5 ( 2002 , SPSS Inc , Chicago , IL ) . RESULTS Percentage of students eligible for  free or reduced-price meals  and  timing of lunch  were significant predictors of a la carte sales . Enrollment was negatively associated with number of vending machines per student . The number of less nutritious food items offered in vending machines and existence of soft drink machines owned by soft drink companies , for which the school receives a percent of sales , both predicted number of vending machines per student . Enrollment was inversely related to average daily participation in school lunch . The percentage of students eligible for free/reduced-price meals and enforcement of a policy prohibiting parents or students from bringing food into the cafeteria 
    Output:
    
The studies addressing price incentives suggest that such incentives  are effective for altering consumption in the school setting .
Other types of economic incentives have been included in combined intervention schemes , but the inclusion of other intervention elements makes it difficult to draw conclusions about the effectiveness of the economic incentive instruments per se in these studies