***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 The effects of weight-loss attempts on long-term weight gain remain unclear . OBJECTIVE The objective was to study prospect ively how attempts to lose weight relate to future risk of major weight gain ( > 10 kg ) and whether familial factors affect this relation . DESIGN Participants in the Finnish Twin Cohort ( 3536 men and 4193 women aged 18 - 54 y at baseline ) were followed up for 6 - 15 y. The role of familial factors was studied in 1705 twin pairs in this cohort who were discordant for weight-loss attempts at baseline . Baseline ( 1975 ) and follow-up ( 1981 and 1990 ) data -including  weight , weight-loss attempts ( dieting ) , and selected confounders-were  obtained via mailed question naires . RESULTS Average weight gain was at most weakly associated with weight-loss attempts . The risk of major weight gain for subjects attempting to lose weight at baseline was greatest among initially young ( 18 - 29 y ) men ( over 6 and 15 y , respectively-odds ratios : 2.01 and 1.74 ; 95 % CI : 1.13 , 3.57 and 1.11 , 2.75 ) and middle-aged ( 30 - 54 y ) women ( over 6 and 15 y , respectively-2.43 and 1.52 ; 1.33 , 4.42 and 1.06 , 2.22 ) and persisted after potential confounders were controlled for . These risks decreased and became nonsignificant in the pairwise twin analysis , suggesting that the relation between dieting and subsequent major weight gain may also have a familial component . CONCLUSIONS Weight-loss attempts may be associated with subsequent major weight gain , even when several potential confounders are controlled for . Genetic and familial factors may contribute to this association STUDY OBJECTIVE Attitudes and practice s concerning weight control in British adults were examined to test the hypothesis that variation in concern about weight and deliberate weight control might partly explain the socioeconomic status ( SES ) gradient in obesity . Higher SES groups were hypothesised to show more weight concern and higher levels of dieting . SETTING Data were collected as part of the monthly Omnibus Survey of the Office of National Statistics in March 1999 . PARTICIPANTS A stratified , probability sample of 2690 households was selected by r and om sampling of addresses in Britain . One r and omly selected person in each household was interviewed at their home . MAIN RESULTS As predicted , higher SES men and women had higher levels of perceived overweight , monitored their weight more closely , and were more likely to be trying to lose weight . Higher SES groups also reported more restrictive dietary practice s and more vigorous physical activity . CONCLUSIONS The results are consistent with the idea that part of the protection against weight gain in higher SES groups could be a higher frequency of weight monitoring , a lower threshold for defining themselves as overweight , and a greater likelihood of deliberate efforts at weight control OBJECTIVE : To assess weight perceptions , weight concerns and weight control behaviours and related beliefs in a representative sample of adults . DESIGN : Cross-sectional postal survey . SETTING : The survey was conducted between October and December 1997 in the state of Victoria , Australia . SUBJECTS : A total of 2500 subjects were selected at r and om from the Australian electoral roll ; 900 provided usable responses . RESULTS : At the time of the survey , 2.7 % of respondents were trying to gain weight , 26.6 % were trying to avoid gaining weight , 22.9 % were trying to lose weight and 47.9 % were not doing anything for their weight . Men ( 47.2 % ) were less likely than women ( 55.3 % ) to be attempting any form of weight control . Watching the type of food eaten ( 95.6 % ) ,  reducing dietary fat intake  ( 87.3 % ) and engaging in physical activity or exercise  ( 84.4 % ) were the most common weight control strategies used . Potentially harmful strategies , such as self-induced vomiting and smoking , were used by relatively few respondents . Many adults believed that vigorous activity ( 26.8 % ) and total omission of fat from the diet ( 35.3 % ) are necessary in order to lose weight . CONCLUSIONS : Attempts at weight control are common in the community . However , many men , including men who are already overweight , appear to be unconcerned about their weight . Obesity prevention initiatives should attempt to influence individuals ' weight-related beliefs and behaviours , as well as seeking to change policies and environments to better support weight control Recent surveys have shown that approximately 40 % of adult women and 20 % of adult men report that they are currently trying to lose weight [ 14 ] . A greater percentage of adult Americans engage in weight-loss behavior  over the course of a year , yet little progress has been made toward meeting national health objectives and toward reducing the prevalence of obesity in the general public [ 5 ] . This disparity raises public health questions about possible consumer protection and consumer education strategies to remedy this unsatisfactory state of affairs . The development of such strategies is h and icapped , however , because little is known about what people actually do when they say that they are trying to lose weight . The 1992 Weight Loss Practice s Survey ( WLPS ) , sponsored jointly by the Food and Drug Administration ( FDA ) and the National Heart , Lung , and Blood Institute ( NHLBI ) , interviewed people who were trying to lose weight and asked about more than 35 specific practice s that might be used as part of a weight-loss plan ( Food and Drug Administration ; National Heart , Lung , and Blood Institute . Weight Loss Practice s Survey , 1991 . Unpublished data ) . The WLPS used a national probability sample of U.S. adults and dedicated the entire question naire to weight-loss issues . In addition to a detailed inventory of weight-loss practice s , the WLPS obtained information about individual characteristics such as current weight , weight-loss history , demographic profile , motivations to lose weight , sources of information , and knowledge about diet and health . The survey was design ed to estimate the relative prevalence of different types and combinations of practice s among weight-loss practitioners and to describe the relations between individual characteristics and various features of weight-loss regimens . We present a broad overview of the survey results . The key classification variables used were sex , weight status defined by ranges of body mass index ( BMI ) , and regimen characteristics . Analyses examined whether and how these variables are associated with weight-loss practice s. Methods Data for the WLPS were collected in the continental United States from September to mid-November 1991 . Respondents were noninstitutionalized , civilian adults , 18 years or older , who were contacted and interviewed by telephone . A two-stage sampling procedure was used to select the respondents to be interviewed [ 6 ] . The first stage involved the selection of a sample of telephone numbers through r and om-digit dialing procedures . In the second stage , a design ated respondent was selected r and omly from all adults in the household . The design ated respondent was asked , Are you right now trying to lose weight ? Respondents who answered yes continued the interview . Of the 10 840 households contacted , 72 % completed the interview through the weight-loss screening question . Of those design ated respondents who said that they were attempting to lose weight , 95 % completed the WLPS interview . The total sample of 1431 persons trying to lose weight consisted of 1030 women and 401 men . Our analysis estimated the level or prevalence of weight-loss variables within each of 12 population subgroups defined by sex and three classifications of BMI ( weight [kg]/height [ m2 ] ) and three classifications of regimen characteristics . Self-reported height and weight were used to calculate BMI . Respondents were assigned to one of three categories ( BMI < 26 , 26 to < 30 , and 30 ) . We classified persons with a BMI between 26 and 30 as overweight and those with a BMI of 30 or more as obese [ 7 ] . Because BMI was based on self-reported weights , overweight and obesity were probably underestimated . Persons consistently under-report their true weights by approximately 1 kg ; however , correlations between reported weights and measured weights are typically quite high , ranging between r = 0.96 and r = 0.99 [ 8 ] . The regimen characteristics used for classification were as follows : whether respondents had combined dieting ( defined as eating differently from the way you usually eat for the sake of losing weight ) and exercise ( as called for by most weight-loss guidelines ) [ 7 , 9 ] ; whether respondents had been on their current weight plan for at least 1 year ( an indication of a long-term commitment ) ; and whether respondents engaged in one or more practice s that might be considered question able in some circumstances . Practice s were classified as question able based on the possibility of abuse . Question able practice s included fasting for 24 hours or longer , taking diet supplements such as high-protein or fiber supplements , using any type of diet-aid pill ( for example , appetite suppressants , diuretics , or thyroid pills ) , vomiting after eating , taking laxatives , or using special weight-loss devices  . Such practice s have been associated with health problems [ 10 ] but could be considered acceptable elements of a weight-loss plan if used judiciously or while under professional supervision . For example , although it is acceptable to use diet supplements to supplement a healthy diet , it is unacceptable to use such supplements as a substitute for food to lose weight . The regimen classifications described here are not mutually exclusive and any possible combination of the three characteristics could describe an individual weight-loss plan . All survey estimates were weighted to the 1990 census distribution on sex , race , age , and education . Because of item nonresponse , the number of respondents varied slightly between analyses . Respondents were excluded only from those analyses for which they failed to answer the relevant items . Results Characteristics of Weight-Loss Practitioners The population prevalence of active weight-loss attempts was calculated by dividing the number of persons who reported attempting to lose weight by the total number of design ated respondents who were contacted . Overall , 33 % of women and 20 % of men reported that they were currently trying to lose weight . The relative prevalence of weight-loss plans by BMI group and regimen classification variables are shown in Table 1 . More than two thirds of weight-loss practitioners combined diet and exercise in their weight-loss plan , 30 % had been on the current plan for 1 year or more , and 20 % engaged in some kind of question able weight-loss practice . Table 1 also shows the distribution of  weight-loss  plans by demographic characteristics and regimen features . Compared with the general population , persons trying to lose weight were more likely to be women , young to middle-aged , and better educated . Most men were in one of the two higher BMI categories . In contrast , about one half of women were in the lowest BMI category ; that is , a substantial percentage of women who are trying to lose weight may not be overweight . Table 1 . Body Mass Index Group and Regimen Features by Demographic Characteristics and Regimen Features : Percentage Distributions of Weight-Loss Practitioners * Younger persons were more likely to include both diet and exercise in their regimens but were less likely than older respondents to be on long-term regimens . More educated practitioners were more likely to be nonoverweight as determined by BMI . Weight-loss practitioners with more education were also more likely to combine diet and exercise in their weight-loss plans and were less likely to engage in question able practice s. Blacks who reported trying to lose weight were much more likely to be overweight and to engage in question able practice s than were whites . Previous Weight-Loss Experience Characteristics Respondents reported they had spent an average of 6 months of the past year trying to lose weight , had made an average of more than two weight-loss attempts during the past 2 years , and had tried their current weight-loss plan once before . Women reported more previous weight-loss attempts and more time spent trying to lose weight than did men . Tables 2 and 3 show the means for these and other survey variables by BMI groups and regimen features for women and men , respectively . Table 2 . Characteristics of Current Weight-Loss Plan by Body Mass Index Group and Regimen Type for Women * Duration of Current Weight-Loss Plan The average duration of the current weight-loss attempt was between 5 and 6 months for both women and men . Duration of the current weight-loss attempt decreased dramatically as BMI level increased for both women and men . Weight-loss practitioners with higher BMI levels engaged in more frequent weight-loss attempts of shorter duration than did those with lower BMI levels , who tended to remain in a given plan for longer periods . Weight-Loss Goals Respondents reported how much weight they had lost with their current plan and how much more weight they hoped to lose . The sum of the two responses defined their weight-loss goal . Weight-loss goals were strongly related to weight status . For both women and men , as BMI levels increased , so did the amount of weight they hoped to lose . Weight-loss goals ranged from around 10 kg for those with a BMI of less than 26 to an average of almost 30 kg for those with a BMI of 30 or more . In contrast to the threefold variation in weight-loss goals , the variation in achieved weight-loss between BMI groups was modest , averaging less than 2 kg for women and less than 3 kg for men . The weight-loss goals of persons at the higher BMI levels appeared unrealistic , given the amounts of weight that they had lost so far . Information-seeking Behavior Approximately 40 % of those engaged in a weight-loss attempt said that they had checked with their doctor before trying to lose weight . For both women and men , the likelihood of checking with a physician increased with BMI . Less than one third of respondents reported looking for information about how to lose weight from expert sources such as physicians , nutritionists , other health professionals , or specialized reading . Most respondents obtained information from informal sources such as friends , family members , PURPOSE This study evaluated exercise-related predictors of  successful long-term weight control in women by analyzing the extent to which sustained exercise participation and self-determination theory (SDT)- 
    Output:
    
To our knowledge , this is the first systematic review to investigate weight control attempts worldwide .
Key strategies and motives were identified which have implication s for future public health initiatives on weight control