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ORIGINAL RESEARCH COMMUNICATION |
1 From INSERM U258, IFR69, Villejuif, France (BLG and MAC); Paris XI University, Orsay, France (BLG and MAC); the Nutrition Department, Hôtel-Dieu Hospital, Paris, France (AB); Paris VI University, Paris, France (AB); Nutrition Department, University Hospital, Lille, France (MR); Health Care Research Unit, Sahlgrenska University Hospital, Göteborg University, Göteborg, Sweden (JK); and the Association Fleurbaix-Laventie Ville Santé, Laventie, France (JMB)
2 Supported by grants from the Centre for Sugar Research and Information, the Centre for Beer Scientific Information, Groupe Fournier, Knoll, Lesieur, Nestlé France, and Roche Diagnostics and by grants from the Association de Langue Française pour lÉtude du Diabète et du Métabolisme and the Mutuelle Générale de lÉducation Nationale (to MAC).
3 Reprints not available. Address correspondence to B de Lauzon-Guillain, INSERM U258, 16 avenue Paul-Vaillant Couturier, 94807 Villejuif Cedex, France. E-mail: delauzon{at}vjf.inserm.fr.
| ABSTRACT |
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Objective: We assessed the relations between eating behavior (EB) and adiposity in a general population over a 2-y period.
Design: We recruited 466 adults and 271 adolescents in 1999 on a geographical basis to participate in a longitudinal study. At the initial examination and 2 y later, they answered an EB questionnaire, the Three-Factor Eating QuestionnaireR18, which measured cognitive restraint (CR), uncontrolled eating, and emotional eating. On the same occasions, several measures of adiposity were also obtained: body mass index (BMI; in kg/m2), waist circumference, the sum of 4 skinfold thicknesses, and percentage body fat. Relations between EB and adiposity were tested separately in adults and adolescents by using mixed linear regressions after adjustment for age, sex, and (in adolescents) Tanner pubertal stage.
Results: At baseline, CR was positively associated with BMI in normal-weight subjects (
BMI: 21.4 in the lowest to 23.3 in the highest CR quintile; P < 0.001) but not in overweight adults (P = 0.25). Initial CR did not predict change in adiposity variables (BMI change: P = 0.79 in adults, P = 0.57 in adolescents and young adults). Conversely, a high initial BMI was associated with a larger increase in CR (ß = 20.1, P < 0.0001 in adults; ß = 21.7, P = 0.003 in adolescents and young adults).
Conclusions: Restrained eating is strongly associated with adiposity in normal-weight subjects but not in overweight subjects. However, restrained eating does not promote weight gain.
Key Words: Eating behavior adiposity adult adolescent longitudinal study
| INTRODUCTION |
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In modern societies characterized by abundant and easily accessible foods, restrained eating may become an adaptive behavior to limit weight gain. Whether this eating behavior is on average a successful strategy in the general population or whether it, rather, leads in the long term to excessive weight gain is controversial. Several studies supported a positive cross-sectional association between restrained eating and BMI (5, 6), whereas others found no significant relation (7, 8) or inverse relations (9, 10).
Most longitudinal studies of the association of restrained eating with weight change were conducted during weight-reduction programs (1114), and few of them took place in the general population. Among the latter, one study that included only women (15) showed that restrained eating was not an independent predictor of subsequent weight gain. The Quebec Family Study showed a positive association between initial restrained eating and weight change, but only in women (16). That study also showed that both weight status and sex may modulate the associations between restrained eating and BMI. In fact, restrained eating was positively correlated with BMI in normal-weight women, whereas an inverse relation between restrained eating and BMI was observed in obese men (17).
The study of restrained eating in the population presents some methodologic difficulty. Three self-rating questionnairesthe Restraint Scale (18), the Dutch Eating Behavior Questionnaire (19), and the Three-Factor Eating Questionnaire (TFEQ; 20)were used in the study of eating behavior. The TEFQ was developed in response to psychometric problems in the Restraint Scale (20). It was composed of 51 items and comprised 3 scales: restraint, hunger, and disinhibition. Karlsson et al (21) developed from the TFEQ a short, revised 18-item questionnaire, the TFEQ-18, which comprised 3 scales: cognitive restraint (conscious restriction of food intake to control body weight or to promote weight loss), uncontrolled eating (tendency to eat more than usual because of a loss of control over intake), and emotional eating (overeating during dysphoric mood states, eg, when feeling lonely, depressed, or anxious).
We previously showed that the 3 scores of the TFEQ-18 were associated with distinct food and energy intake patterns in a population sample (22). To explore the causality in the relation between restrained eating and BMI, our aim was to investigate, in a longitudinal study, whether cognitive restraint and other eating behaviors were predictive of changes in fat mass over a 2-y period in the general population. We also analyzed the opposite relation and tested the value of initial adiposity in predicting the changes in restrained eating over time. Finally, because uncontrolled eating is often seen as a consequence of restrained eating, we also analyzed whether cognitive restraint scores were predictive of an increase in uncontrolled eating over time.
| SUBJECTS AND METHODS |
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8 y, from families living in the cities of Fleurbaix and Laventie (France) and smaller surrounding cities who had participated in a previous study, the FLVS I (23). The first study was a follow-up of children who had been involved in a nutritional education program at school. It involved all 579 families who had
1 child in primary school in 1992 in Fleurbaix or Laventie. FLVS II was proposed to 393 families who had not moved and who could be reached in 1999. Two hundred ninety-four (75%) of the 393 families agreed to participate. The main differences between the families who participated in FLVS II and those who did not were that participating families were more likely to reside in Fleurbaix and Laventie than in the smaller cities, and the frequency of overweight children in 1992 was significantly lower in participating than in nonparticipating families (8% and 13%, respectively; P = 0.01). Other criteria, such as parents overweight status and the subjects age and sex, did not differ significantly between the 2 groups. Written informed consent was obtained from all subjects in both FLVS I and FLVS II. The study protocol of FLVS II was approved by the Ethics Committee of Lille in July 1998, and the data files were approved by the CNIL (French committee for rights concerning computerized data).
Anthropometric data
Anthropometric data were collected by trained technicians. Height, weight, waist circumference, and 4 skinfold thicknesses (biceps, triceps, subscapular and suprailiac) were measured at baseline and after 2-y follow-up. Weight (to the nearest 0.1 kg) and percentage body fat (%BF) were measured by using the Tanita TBF 310 tetrapolar foot-to-foot bioimpedance analyzer (Tanita Corp, Neuilly-sur-Seine, France) while the subjects wore light clothes and were barefoot. Height was measured to the nearest 5 mm and waist circumference to the nearest 1 cm. Skinfold thickness was measured in duplicate to the nearest 0.1 mm by using Harpenden calipers at 4 locations on the left side of the body: triceps (posterior aspect of the arm, at the midpoint between the acromion and the olecranon), biceps (anterior aspect of the arm, at the midpoint between the acromion and the olecranon), subscapular (1 cm below the inferior angle of the scapula), and suprailium (1 cm over the iliac crest, at the midaxillary line). Several adiposity variables were used in the analysis: the sum of 4 skinfold thicknesses (as a measure of subcutaneous adiposity), body mass index (BMI; in kg/m2) and %BF (both as estimates of total fat mass), and waist circumference (as an estimate of the amount of abdominal fat). Adults with a BMI
25 were classified as overweight.
Revised Three-Factor Eating Questionnaire
Eating behavior was assessed by using a French translation of the TFEQ-R18 (21). The translation was obtained by using common procedures for cross-cultural adaptation, including back-translation by a native English speaker. The questionnaire refers to current dietary practice and measures 3 aspects of eating behavior: cognitive restraint (6 items), uncontrolled eating (9 items), and emotional eating (3 items). Its validity and applicability to the French general population were described previously. The reliability coefficients of internal consistency (Cronbachs alpha) for each of the 3 scales were above the 0.70 standard and below the 0.90 upper limit recommended for individual assessment (22). Subjects answered this questionnaire in 1999 and again in 2001.
Participants
Only adolescents (aged
14 y) and adults answered the TFEQ-R18 and were therefore considered for this analysis. Among the 887 subjects who participated in the study in 1999, 14 were excluded because of missing sociodemographic or anthropometric data, and 17 did not complete the TFEQ-R18. One hundred nineteen subjects did not participate in the study in 2001 and were consequently excluded from the longitudinal analysis. Excluded subjects differed significantly from included subjects by age (
: 33.5 and 29.9 y, respectively; P = 0.003): 42% of subjects aged 2030 y in 1999 were nonrespondent in 2001 because they had left the family home in the meantime. However, they did not differ significantly from the subjects excluded from the analysis by sex (47% and 52% of subjects who responded and did not respond, respectively, were male; P = 0.26) or and body mass index (BMI; in kg/m2) after adjustment for age (23.1 and 23.4, respectively; P = 0.39).
The sample analyzed was composed of 466 parents [207 (44.4%) men and 259 (55.6%) women] in the adult group (aged 3167 y) and 271 offspring [139 (51.3%) boys and 132 (48.7%) girls] in the adolescent and young adult group (aged 1424 y).
Statistical analysis
Separate analyses were conducted in the adult group and in the adolescent and young adult groups. Several analyses were also performed separately in normal weight and overweight adults because the associations differed according to initial overweight status (see Results). There were too few overweight adolescents or young adults and too few obese adults (BMI
30) for a meaningful analysis using these categories. Because initial eating behavior scores were not normally distributed, subjects were divided into 5 categories by quintiles of each eating behavior score distribution, specific to adults and adolescents groups, and by initial overweight status when analyses were performed separately in normal-weight and overweight adults. Logarithmic transformations of initial adiposity variables except %BF were performed because of the skewed distribution. The 2-y changes (2-y change = final value initial value) in eating behavior scores and in adiposity values were quite normally distributed and analyzed as continuous variables after adjustment for their initial value. Adjusted means of initial adiposity and changes in adiposity were computed by categories of initial eating behavior scores, using linear regressions after adjustment for a possible residual age effect within each group, for sex, and (in adolescents) for Tanner puberty stage. To take into account correlations between siblings or between spouses, a family variable was introduced as a random effect at the level of the intercept, and the other variables were declared as fixed effects (SAS PROC MIXED). Similar models were used to study the relations between changes in eating behavior over 2 y, the explained variables, and initial adiposity. We also performed multivariate logistic regressions to assess whether baseline uncontrolled eating was associated with baseline restrained eating. The odds ratio (OR) quantified the risk of being in the upper 2 quintiles of uncontrolled eating in comparison with the lower quintiles. The Generalized Estimating Equations (SAS PROC GENMOD) were used to take into account the familial correlations between individuals (24). We used SAS software (version 8.2; SAS Institute, Cary, NC) for the analyses.
| RESULTS |
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| DISCUSSION |
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Restrained eating may be defined as a self-initiated attempt to restrict food intake for the purpose of weight control. This strategy to prevent weight gain is more developed in subjects who are prone to put on weight. Cross-sectional studies have shown that restrained eating is higher in those with greater adiposity (5, 25, 26), and our cross-sectional results in normal-weight subjects are in accordance with these previous studies. Moreover, our longitudinal study shows that adults with the greatest initial adiposity are more likely to increase their cognitive restraint score over time. Shunk and al (27) previously showed that differences in weight status temporally preceded differences in restrained eating among 59-y-old girls. Our results in the adolescents and young adults were quite similar to those in the normal-weight adults, which showed that the eating behaviors we studied were already developed in adolescents and young adults.
In our general population, initial restrained eating did not predict subsequent weight change. Therefore, this strategy did not appear to be truly deleterious with respect to weight control. On the other hand, we found no evidence that, for a given degree of adiposity, those with higher score were more successful in controlling their weight over time. Previous studies already showed that initial restrained eating alone did not favor weight gain (15, 28). However, the lack of association is still controversial and may depend on the studied population. Drapeau et al (16) found that initial restrained eating was positively related to subsequent weight gain in women but negatively related in men.
The literature provides a greater consensus that any deleterious effects of restrained eating are mediated by the disinhibition effect (2, 3, 29, 30). We could not confirm these results. Actually, high initial cognitive restraint scores were indeed associated with high initial uncontrolled-eating scores. However, initial restrained eating was not predictive of a subsequent change in uncontrolled eating. Moreover, contrary to previous studies (15, 31), initial uncontrolled-eating scores were not predictive of adiposity change. This discrepancy could partially be due to differences in study designs. In fact, in one of the previous studies (15), weight gain was assessed retrospectively, and, consequently, disinhibition was positively related to previous and not subsequent weight gain. The other study (31) was conducted in obese subjects during a weight reduction program, whereas our study was conducted prospectively in a general population. Finally, Van Strien et al (32) showed that young adult restrained eaters were highly susceptible to failure of restraint only when restrained eating was associated with other eating behaviors, such as emotional eating, external eating, or binge eating. Several studies found that the prevention of weight gain was more successful when a persons eating control was flexible and not associated with disinhibition (3, 8, 14, 32). We were not able to show, in the adults and adolescents with high cognitive restraint (cognitive restraint score above the group-specific median) in the current study, a greater adiposity change in those with a high uncontrolled-eating scores (uncontrolled-eating score above the group-specific median) than in those with low uncontrolled-eating scores (data not shown). This lack of association may be due to the small size of our sample. Moreover, our subjects had cognitive restraint and uncontrolled-eating scores that were perhaps too low to enter this restrained eating-disinhibition cycle. Restrained eating may also be useful for attenuating the effects of overeating (13, 15, 33).
Our study has some limitations: the FLVS Study was a longitudinal study, and children in the families included in the FLVS Study had been involved in a school nutritional program between 1992 and 1997. It is likely that the participants selected for our study represent a group of subjects who were more health conscious than the general population. The use of BMI to assess longitudinal changes in fat mass in adolescents is questionable because body-composition changes substantially with aging in that group (34). The use of different adiposity variables allows a global approach to changes in adiposity in adolescents.
In conclusion, restrained eating is strongly associated with higher fat mass in normal-weight subjects but not in overweight subjects. Moreover, heavier subjects present a greater increase in restrained eating over time than leaner ones. Conversely, initial restrained eating is not associated with weight gain. Differences in adiposity level precede differences in restrained eating. Our results suggest that, in normal-weight subjects, restrained eating does not promote weight gain. Results on the deleterious effect of highly restrained eating found in obese subjects should not be extended to normal weight subjects.
| ACKNOWLEDGMENTS |
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The FLVS Study group was responsible for study design and data collection. JMB participated in the conception and design of the study and reviewed the manuscript. JK helped with the preparation and the use of the French-language version of the TFEQ-R18 and reviewed the manuscript. MAC, AB, and MR were involved in all aspects from study conception to manuscript writing. BLG performed the statistical analyses and wrote the manuscript. None of the authors had a personal or financial conflict of interest.
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