***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: Objectives This study examined associations between high school students ' lunch patterns and vending machine purchases and the school food environment and policies . Methods A r and omly selected sample of 1088 high school students from 20 schools completed surveys about their lunch practice s and vending machine purchases . School food policies were assessed by principal and food director surveys . The number of vending machines and their hours of operation were assessed by trained research staff . Results Students at schools with open campus policies during lunchtime were significantly more likely to eat lunch at a fast food restaurant than students at schools with closed campus policies ( 0.7 days/week vs. 0.2 days/week , p < .001 ) . Student snack food purchases at school were significantly associated with the number of snack machines at schools ( p < .001 ) and policies about the types of food that can be sold . In schools with policies , students reported making snack food purchases an average of 0.5 ± 1.1 days/week as compared to an average of 0.9 ± 1.3 days/week in schools without policies ( p < .001 ) . In schools in which soft drink machines were turned off during lunch time , students purchased soft drinks from vending machines 1.4 ± 1.6 days/week as compared to 1.9 ± 1.8 days/week in schools in which soft drink machines were turned on during lunch ( p = .040 ) . ConclusionS chool food policies that decrease access to foods high in fats and sugars are associated with less frequent purchase of these items in school among high school students . Schools should examine their food-related policies and decrease access to foods that are low in nutrients and high in fats and sugars OBJECTIVE . To assess whether weight-related teasing predicts the development of  binge eating , unhealthy weight control behaviors , and frequent dieting  among male and female adolescents . METHODS . A prospect i ve study was conducted with an ethnically and socioeconomically diverse sample of 2516 adolescents who completed surveys at both time 1 ( 1998–1999 ) and time 2 ( 2003–2004 ) of the Project EAT ( Eating Among Teens ) study . RESULTS . In 1998–1999 , approximately one fourth of participants reported being teased about their weight at least a few times a year . After adjustment for age , race/ethnicity , socioeconomic status ( SES ) , and BMI , boys who were teased about their weight were more likely than their peers to initiate binge eating with loss of control and unhealthy weight control behaviors 5 years later . The predicted prevalence for incident binge eating behaviors with loss of control among boys who were teased was 4.1 % as compared with 1.4 % for those who were not teased , after adjustment for age , race/ethnicity , SES , and BMI . For unhealthy weight control behaviors at time 2 , the predicted prevalence was 27.5 % among boys who were teased and 19.3 % for boys who were not teased , after adjustment for age , race/ethnicity , SES , and BMI . Girls who were teased were more likely than their peers to become frequent dieters . The predicted prevalence for incident frequent dieting among girls who were teased was 18.2 % as compared with 11.0 % for those who were not teased , after adjustment for age , race/ethnicity , SES , and BMI . CONCLUSIONS . Weight teasing in adolescence predicts disordered eating behaviors at 5-year follow-up . The patterns of these associations differ by gender . Reducing teasing through educational interventions and policies may reduce the level of disordered eating behaviors among youths 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 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 OBJECTIVES We evaluated an environmental intervention intended to increase sales of lower-fat foods in secondary school cafeterias . METHODS Twenty secondary schools were r and omly assigned to either an environmental intervention or a control group for a 2-year period . The intervention increased the availability of lower-fat foods and implemented student-based promotions . RESULTS A steeper rate of increase in sales of lower-fat foods in year 1 ( 10 % intervention vs -2.8 % control , P = .002 ) and a higher percentage of sales of lower-fat foods in year 2 ( 33.6 % intervention vs 22.1 % control , P = .04 ) were observed . There were no significant changes in student self-reported food choices . CONCLUSIONS School-based environmental interventions to increase availability and promotion of lower-fat foods can increase purchase of these foods among adolescents OBJECTIVE This study examined the types and extent of competitive foods available in public high schools in Pennsylvania . DESIGN We developed , pilot tested , and distributed surveys to school foodservice directors in a r and om sample of 271 high schools in Pennsylvania . SUBJECTS Two hundred twenty-eight surveys were returned , for a response rate of 84 % . Statistical analyses were performed : Descriptive statistics were used to examine the extent of competitive food sales in Pennsylvania public high schools . The survey data were analyzed using SPSS software version 11.5.1 ( 2002 , SPSS base 11.0 for Windows , SPSS Inc , Chicago , IL ) . RESULTS A la carte sales provide almost dollar 700/day to school foodservice programs , almost 85 % of which receive no financial support from their school districts . The top-selling a la carte items are " hamburgers , pizza , and s and wiches . " Ninety-four percent of respondents indicated that vending machines are accessible to students . The item most commonly offered in vending machines is bottled water ( 71.5 % ) . While food items are less often available through school stores and club fund-raisers , c and y is the item most commonly offered through these sources . CONCLUSIONS Competitive foods are widely available in high schools . Although many of the items available are low in nutritional value , we found several of the top-selling a la carte options to be nutritious and bottled water the item most often identified as available through vending machines OBJECTIVES This study described the food environment in 20 Minnesota secondary schools . METHODS Data were collected on school food policies and the availability and nutritional content of foods in school à la carte ( ALC ) areas and vending machines ( VMs ) . RESULTS Approximately 36 % and 35 % of foods in ALC areas and in VMs , respectively , met the lower-fat criterion ( < or = 5.5 fat grams/serving ) . The chips/crackers category constituted the largest share of ALC foods ( 11.5 % ) . The median number of VMs per school was 12 ( 4 soft drink , 2 snack , 5 other ) . Few school food policies were reported . CONCLUSIONS The availability of healthful foods and beverages in schools as well as school food policies that foster healthful food choices among students needs greater attention The objectives of this study were to describe the extent , nature , and enforcement of school competitive food policies in Pennsylvania public high schools and to determine if there are differences between school foodservice directors ' and principals ' perceptions of the existence and enforcement of these policies . A survey was distributed to 271 school foodservice directors and 100 principals in a representative , r and om sample of high schools . Two hundred twenty-eight school foodservice directors ( 84 % ) and 79 principals ( 79 % ) returned surveys . Descriptive statistics , chi2 analyses , and a proportions test were done using SPSS statistical software ( SPSS base 11.5 for Windows , 2002 , SPSS Inc , Chicago , IL ) . Few nutrition policies were reported related to setting nutritional st and ards for competitive foods ( 0.5 % to 15.0 % ) . Respondents ' reporting of existence of policies not always enforced ranged from 0 % to 12.8 % . School foodservice directors reported uncertainty about existence of several policies outside their direct domain , but with potential effect on school meals participation . Differences were found between school foodservice directors ' and principals ' reporting of policies , with principals more often reporting policy existence and enforcement . These findings suggest the need for communication , both about existence of policies and chain of comm and in enforcement of policies . Given the local wellness policy provision of the Child Nutrition and WIC Reauthorization Act of 2004 , opportunities exist for nutrition professionals to contribute to development of policies that influence the nutritional quality of school foods 
    Output:
    
RESULTS Thus far , few data exist to substantiate the concern that changes in nutrition st and ards in schools lead to a loss in total revenue .
CONCLUSIONS A renewed focus on school policies related to health provides the opportunity for research ers to investigate how nutrition-related policy change can affect , if at all , food service and overall school revenues