obesity is a major risk factor for chronic diseases , and it also plays a central role in both insulin resistance and metabolic syndrome , which includes hyperinsulinemia , hypertension , hyperlipidemia , and type 2 diabetes mellitus . it was recently reported that the metabolic and physiologic abnormalities associated with obesity in adolescence ( e.g. , hypertension , dyslipidemia , and type 2 diabetes ) tend to track into adulthood , along with the condition of obesity itself . moreover , independent of adult obesity status , adolescent obesity increases the long - term risk of adult mortality and morbidity . overweight and obesity have also been reported to be associated with a variety of lifestyle factors [ 413 ] , among which , eating behavior has long been identified as a factor . several studies have reported an association between eating speed and overweight or obesity [ 911 ] , and eating until full , which refers to consuming a large quantity of food in one meal and is unrelated to eating disorders , has been reported to be associated with overweight [ 12 , 13 ] . however , the effect of eating speed on overweight could depend on the behavior of eating until full , because the total energy intake in those who eat quickly and until full is usually higher than that in those who eat quickly but not until full . reported that both eating quickly and eating until full are associated with overweight among adults , and the combination of the two may have a substantial impact on overweight . for example , fast eating speed may not have a significant effect on overweight if the individual does not eat until full . therefore , when eating speed is evaluated as a risk factor for overweight or obesity , it may be essential to consider eating until full behavior . however , to the best of our knowledge , the combined effect of eating speed and eating until full behavior on overweight among adolescents has yet to be reported . accordingly , the aim of the present study was both to investigate the relationship between eating behaviors ( eating speed or eating until full ) and overweight and to examine the effect of the combined behaviors on overweight among population - based adolescents in japan . in addition to the annual national health checkups performed in accordance with the school health law of japan , the town of ina , located in saitama prefecture , has conducted a unique health - promotion program since 1994 . the program consists of a questionnaire survey , blood test , and physical examination for both fourth and seventh graders . study subjects comprised a total of 3256 seventh - grade school children ( age range , 12 - 13 years ) from ina between 1999 and 2008 ( n = 306 in 1999 ; 309 in 2000 ; 298 in 2001 ; 317 in 2002 ; 293 in 2003 ; 315 in 2004 ; 312 in 2005 ; 354 in 2006 ; 380 in 2007 ; and 372 in 2008 ) . informed consent was obtained from the parent or guardian of each subject prior to their participation in the study . the study protocol was approved by the medical ethics committee of showa university school of medicine . a self - administered questionnaire was distributed to each subject by a teacher in the junior high school . each subject and a parent or guardian completed the questionnaire , which was composed of the following two sections : one ( on the front of the questionnaire ) to be completed by the subject ; and the other ( on the back ) to be completed by the parent or guardian . the questionnaire asked subjects about the following items : sex ; age ; exercise other than physical education class ( daily , sometimes , or none ) ; snacking after dinner ( always , often , seldom , or none ) ; eating speed ; and eating until full behavior . information concerning eating speed was based on three possible responses ( fast , medium , or slow )   to the question  how fast is your eating speed compared to others ?  with regard to eating until full behavior , possible responses were either yes or no . the parent or guardian of each subject was asked to complete a self - administered questionnaire regarding the subject 's birth weight , wake - up time , bedtime , frequency of eating breakfast ( daily , sometimes , or none ) , and whether the child was an only child . the heights and weights of the parents or guardians were also self - reported in the questionnaire . self - reported height and weight are commonly used in epidemiological studies and are generally reliable in japanese men and women . sleep duration was calculated from wake - up time and bedtime , and frequency of eating breakfast was categorized into the following two groups : skipping breakfast ( sometimes and none ) and not skipping breakfast ( daily ) . to protect the privacy of the subjects , height and weight were measured either in the school 's infirmary or in a designated room . for the anthropometric measurements , the subjects wore light clothing and were barefoot height was measured to the nearest 0.1  cm using a stadiometer , and body weight was measured to the nearest 0.1  kg using a scale . body mass index ( bmi ) was calculated as weight ( kg ) divided by height ( m ) squared . childhood overweight ( including obesity ) was determined according to the age- and sex - specific cut - off points proposed by the international obesity task force . the criteria have been used in numerous epidemiological studies for both japanese children and adolescents [ 8 , 2124 ] . based on previous studies for japanese adults [ 25 , 26 ] , parents who had a bmi 25  kg / m were defined as obese . statistical analysis was performed separately for each sex . either the chi - square test or the wilcoxon rank - sum test was used to compare various characteristics between the overweight and nonoverweight groups . a logistic regression model was then employed to evaluate the relationship between eating behaviors and overweight , and both the crude odds ratio ( or ) for overweight and the 95% confidence interval ( 95% ci ) were estimated and subsequently adjusted for potential confounders . variables that had been reported to be associated with overweight [ 4 , 8 , 2730 ] , and that were different between the overweight and the nonoverweight groups ( p value less than 0.05 ) in this study , were considered as potential confounders . these included birth weight , obesity status of the parent , frequency of exercise , and skipping breakfast . all statistical analyses were performed using statistical analysis system ( sas ) software ( version 9.2 ; sas institute inc . , cary , nc , usa ) . among all 3256 subjects , 28 refused to participate in the program ( participation rate : 99.1% ) , and 100 were excluded due to incomplete data . the characteristics of both the overweight and the nonoverweight boys ( n = 1586 ) are shown in table 1 . boys with one or more obese parents were more frequently found to be in the overweight group , and statistically significant differences were observed between the overweight and nonoverweight groups in both birth weight and frequency of exercise . a significantly higher proportion of those who eat quickly was found in the overweight group when compared with the nonoverweight group . furthermore , a higher proportion of subjects who reported eating until full was found in the overweight group ; however , this difference was not statistically significant . the characteristics of both the overweight and nonoverweight girls ( n = 1542 ) are shown in table 2 . similar to boys , girls with one or more obese parents were more frequently found to be in the overweight group , and statistically significant differences were also observed between the overweight and nonoverweight groups in both birth weight and frequency of exercise . a higher proportion of those who skip breakfast and a higher proportion of those who eat quickly were found in the overweight group . the crude and adjusted ors of eating speed or eating until full for overweight are shown in table 3 . when compared to adolescents who reported a medium eating speed , a significantly increased or was found among both boys ( or : 2.65 , 95% ci : 1.873.75 , p < 0.001 ) and girls ( 1.73 , 1.052.85 , p = 0.033 ) in the fast eating speed group , whereas no increased or was observed in the slow eating group , regardless of sex . the adjusted ors of eating speed for overweight were then calculated based on eating until full behavior ( table 4 ) . in boys , a significant increase in the or of a fast eating speed was observed compared with a medium eating speed , regardless of eating until full behavior . furthermore , a more marked increase was observed among those eating until full ( or : 2.78 , 95% ci : 1.764.38 , p < 0.001 ) than among those not eating until full ( 2.43 , 1.414.20 , p = 0.001 ) in the or for overweight . in girls , fast eating speed resulted in a significantly increased or among those eating until full , whereas no significant increase was observed in or among those not eating until full . the ors of eating slowly did not increase among either sex , regardless of eating until full behavior . in this study , some significantly different baseline characteristics were observed between the overweight and nonoverweight groups . for example , adolescents with one or more obese parents were more frequently found in the overweight group . familial variables , especially parental obesity , have been reported to be the most important in relation to childhood obesity , and the association between parental overweight / obesity and childhood overweight / obesity has been reported in a number of studies [ 7 , 8 , 27 , 30 ] . moreover , a relationship has also been reported between overweight and birthweight , exercise , or skipping breakfast among children or adolescents [ 4 , 8 , 29 , 30 ] . therefore , our results were consistent with those from previous studies . furthermore , as shown in table 3 , fast eating speed significantly increased the or for overweight , which is also consistent with results from previous studies [ 8 , 11 , 12 ] . fast eating speed has been shown to be associated with adolescent overweight   and associated with overweight in children . it has also been shown to be a risk factor for obesity among preschool children . one possible mechanism underlying the relationship between fast eating speed and overweight is the increase in energy intake among fast eaters ; this is because energy intake per day increases significantly with an increase in eating speed . in addition , sex differences were observed in the effect of fast eating speed on overweight ( table 3 ) . the adjusted or of fast eating speed for overweight among a previous study reported that men ate faster than women and women took more bites and longer to eat than men . the second reason might be the result of differences between the sexes in food preferences . boys have been shown to prefer meat , processed meat products , eggs , and fatty and sugary foods more than girls . in addition , girls may be more likely to select low calorie foods when they snack due to girls ' preferences in relation to body shape . accordingly , the differences observed between the sexes in the effect of eating speed on overweight may be the result of the differences in eating speed and/or food preferences ; however , further study is needed to elucidate the biological mechanisms underlying these differences . in this study , the effect of eating quickly on overweight varied by eating until full behavior ( table 4 ) . the adjusted or of fast eating speed for overweight was higher among those eating until full than that among those not eating until full . eating quickly can lead to a reduced awareness of the quantity of food consumed , which in turn can lead to consumption of a quantity of food that exceeds the amount necessary for satiety . it has recently been reported that fast eating speed may lead to overeating before the stomach senses fullness [ 9 , 11 ] . moreover , total energy intake has been shown to be higher among individuals who report eating until full than among those who do not . therefore , the amount of food consumed by those who eat quickly and until full could be larger than that consumed by those who eat quickly but do not eat until full . in girls , eating both quickly and until full was associated with an increase in the or for overweight , whereas eating quickly and not until full did not . these results suggest that the combination of eating quickly and until full has a substantial effect on overweight , while not eating until full helps to prevent overweight in girls . however , further study is needed to verify these results because information on total energy intake was not collected in this study . on the other hand , regardless of eating until full or not , no increase was observed in the or of slow eating speed for overweight . eating slowly may help to maximize satiation and thus reduce energy intake during meals . in fact , it was recently reported that linear eaters  that is , people who eat at an approximately constant rate  ate less food when challenged to eat at a lower speed . furthermore , it has been shown that , by eating more slowly , an obese patient can improve his digestion , learn to savor the food , and may eventually achieve a normal state of satiation with less food intake . therefore , the strengths of this study were that the outcome ( overweight or nonoverweight ) was defined by height and weight measurements , and that the effect of the combinations of eating speed and eating until full on overweight was evaluated in over 3000 population - based adolescents . first , information concerning eating speed and eating until full was self - reported and , thus , could be not objectively evaluated . however , a high level of concordance between self - reported and friend - reported rates of eating has been reported . additionally , a statistically positive association between the self - reported rate of eating and energy intake has been recently reported , and self - reported rapid eating has been shown to be associated with both overweight and weight gain [ 8 , 11 , 34 ] . therefore , the findings from this study could be considered reasonable ; however , further prospective or intervention studies are needed to verify our results . for instance , socioeconomic status ( ses ) , which has been reported as being a risk factor for both overweight and obesity [ 39 , 40 ] , was not included as an item in the study questionnaire and therefore not evaluated . third , the present study results were based on data from only one town in japan . therefore , due to cultural differences in eating behavior , applying our results to other populations may be difficult . finally , the present study was a cross - sectional study , and , thus , determining a causal relationship of eating behaviors to overweight was not possible . therefore , the possibility of reverse causality can not be excluded . moreover , the combination of both fast eating speed and eating until full may have a significant effect on overweight among adolescents . decreasing eating speed is therefore suggested to be an effective strategy for the prevention of overweight among adolescents .
objectives . the aim of the present study was to investigate the relationship between eating behaviors and overweight among population - based adolescents in japan . methods . 
 study subjects comprised adolescents in the seventh grade ( age range , 1213 years ) from ina , a town in saitama prefecture , japan , between 1999 and 2008 . the height and weight of the subjects were measured , and information concerning eating behaviors ( eating speed and eating until full ) was obtained using a self - administered questionnaire 
 . results . among boys ( 
 n = 1586 ) , fast eating speed significantly increased the odds ratio ( or ) for overweight when compared with medium eating speed , regardless of eating until full or not ; moreover , a more marked increase in the or was observed among boys eating until full ( or : 2.78 , 95% confidence interval : 1.764.38 ) than among those not eating until full ( 2.43 , 1.414.20 ) . among girls ( n = 1542 ) , fast eating speed led to a significant increase in the or in those eating until full ; however , no significant increases were observed in the or in those eating quickly and not until full 
 . conclusions . among adolescents , 
 fast eating speed was associated with overweight ; furthermore , the combination of both fast eating speed and eating until full may have a significant effect on overweight .