Marc Bénard
email: m.benard@eren.smbh.univ-paris13.fr

Géraldine M Camilleri
email: g.camilleri@eren.smbh.univ-paris13.fr

Fabrice Etilé
email: fabrice.etile@inra.fr

Caroline Mejean
email: c.mejean@eren.smbh.univ-paris13.fr

France Bellisle
email: f.bellisle@eren.smbh.univ-paris13.fr

Gerard Reach
email: gerard.reach@aphp.fr

Serge Hercberg
email: s.hercberg@eren.smbh.univ-paris13.fr

Sandrine Péneau
email: s.peneau@eren.smbh.univ-paris13.fr

Caroline Méjean

Gérard Reach

Association between Impulsivity and Weight Status in a General Population

Keywords: impulsivity, overweight, gender

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Overweight and obesity currently represent a major global health burden and are leading public health issues in many countries [START_REF] Health Organization | Obesity: Preventing and managing the global epidemic. Report of a WHO consultation[END_REF], with associated comorbidities such as cardiovascular disease, type 2 diabetes and cancers [START_REF] Health Organization | Diet, nutrition and the prevention of chronic diseases[END_REF]. Numerous influences contribute to the development of overweight and obesity, among which psychological and behavioral factors.

Impulsivity is a personality trait that is defined as "a predisposition toward rapid, unplanned reactions to internal or external stimuli without regard to the negative consequences of these reactions to the impulsive individuals or to others" [START_REF] Moeller | Psychiatric aspects of impulsivity[END_REF]. It is a multidimensional construct measured with either self-report questionnaires or behavioral tasks [START_REF] Moeller | Psychiatric aspects of impulsivity[END_REF][START_REF] Guerrieri | The effect of an impulsive personality on overeating and obesity: Current state of affairs[END_REF][START_REF] Sharma | Toward a theory of distinct types of "impulsive" behaviors: A meta-analysis of self-report and behavioral measures[END_REF]. The Barratt Impulsiveness Scale Version 11 (BIS-11) [START_REF] Patton | Factor structure of the Barratt impulsiveness scale[END_REF] is the most often used self-report questionnaire to assess impulsivity.

According to this definition, impulsive individuals could present a tendency to have rapid and unplanned reactions toward food, which could lead to overeating and thus obesity. Findings on the association between impulsivity, as measured by the BIS-11, and weight status, however, are limited and divergent. A study has shown a significant higher impulsivity level among overweight subjects compared to normal weight subjects [START_REF] Babbs | Decreased caudate response to milkshake is associated with higher body mass index and greater impulsivity[END_REF]. However, other studies found no significant difference in impulsivity between obese and normal weight participants [START_REF] Loeber | Impairment of inhibitory control in response to food-associated cues and attentional bias of obese participants and normal-weight controls[END_REF], and no significant correlation between impulsivity and BMI [START_REF] Dietrich | Body weight status, eating behavior, sensitivity to reward/punishment, and gender: Relationships and interdependencies[END_REF][START_REF] Van Koningsbruggen | Successful restrained eating and trait impulsiveness[END_REF]. It must be noted that these previous studies were performed on small and specific samples. Divergences in the characteristics of these samples, such as eating disorders [START_REF] Schag | Food-related impulsivity in obesity and Binge Eating Disorder-A systematic review[END_REF] or socio-demographic and lifestyle characteristics, could explain these differences. Studies assessing impulsivity using self-report questionnaires [START_REF] Rydén | Severe obesity and personality: A comparative controlled study of personality traits[END_REF][START_REF] Davis | Sensitivity to reward and body mass index (BMI): Evidence for a non-linear relationship[END_REF][START_REF] Mobbs | Obesity and the four facets of impulsivity[END_REF][START_REF] Gerlach | Personality traits and obesity: A systematic review[END_REF][START_REF] Meule | Facets of impulsivity interactively predict body fat and binge eating in young women[END_REF][START_REF] Terracciano | Facets of personality linked to underweight and overweight[END_REF] other than the BIS-11, or behavioral tasks [START_REF] Nederkoorn | Impulsivity in obese women[END_REF][START_REF] Jarmolowicz | Robust relation between temporal discounting rates and body mass[END_REF] have shown a link with weight status. Impulsive personality has also been associated with a tendency to overeat [START_REF] Guerrieri | The effect of an impulsive personality on overeating and obesity: Current state of affairs[END_REF][START_REF] Yeomans | Impulsivity is associated with the disinhibition but not restraint factor from the Three Factor Eating Questionnaire[END_REF][START_REF] Van Den Berg | Association between impulsivity, reward responsiveness and body mass index in children[END_REF][START_REF] Jansen | High-restrained eaters only overeat when they are also impulsive[END_REF] and with eating disorders [START_REF] Claes | Impulsivity-related traits in eating disorder patients[END_REF][START_REF] Rosval | Impulsivity in women with eating disorders: Problem of response inhibition, planning, or attention?[END_REF][START_REF] Galanti | Test meal intake in obese binge eaters in relation to impulsivity and compulsivity[END_REF].

The potential effect of gender on the association between impulsivity and weight status has rarely been investigated, although gender is known to modify the association between personality dimensions and weight status [START_REF] Faith | Gender differences in the relationship between personality dimensions and relative body weight[END_REF].

The aim of this study was to explore the association between impulsivity using the BIS-11 and weight status, in a large sample of the general French population participating in the NutriNet-Santé cohort. Furthermore, we also assessed whether gender could modify this association.

Materials and Methods

Population

This study was conducted as part of the NutriNet-Santé study, which is a large ongoing web-based prospective cohort started in France in May 2009 with approx. 160,000 participants. The rationale, design and methods of the study have been described elsewhere [START_REF] Hercberg | The Nutrinet-Santé Study: A web-based prospective study on the relationship between nutrition and health and determinants of dietary patterns and nutritional status[END_REF]. Its aim is to explore the relationships between nutrition and health, and more precisely cardiovascular diseases, cancers, mortality and the determinants of eating behavior and nutritional status. Participants are adult volunteers (age ≥18 years) of the general French population with a follow-up of at least 10 years. At inclusion, participants have to complete several self-reported web-based questionnaires to assess their diet, their physical activity, anthropometric measures, lifestyle characteristics, socioeconomic conditions and health status. Participants complete this set of questionnaires every year after inclusion. Finally, another set of optional questionnaires related to determinants of eating behaviors and nutritional status are sent to every participant each month. This study was conducted in accordance with the Declaration of Helsinki, and all procedures were approved by the International Research Board of the French Institute for Health and Medical Research (IRB Inserm n • 0000388FWA00005831) and the Commission Nationale Informatique et Libertés (CNIL n • 908450 and n • 909216). Electronic informed consent was obtained from all participants.

Measures

Impulsivity

To assess impulsivity, the French version of the BIS-11 questionnaire (derived from the French version of the BIS-10 questionnaire) [START_REF] Baylé | Factor analysis of french translation of the Barratt impulsivity scale (BIS-10)[END_REF] was administered to all participants of the NutriNet-Santé study in June 2014 with a maximum answer delay of 6 months. The BIS-11 is the most often used self-report questionnaire to assess impulsivity [START_REF] Stanford | Fifty years of the Barratt Impulsiveness Scale: An update and review[END_REF]. It is a 30-item self-report questionnaire [START_REF] Patton | Factor structure of the Barratt impulsiveness scale[END_REF] developed to assess the personality construct of impulsivity and its 3 aspects: attentional impulsiveness (focusing on the task at hand), motor impulsiveness (acting without thinking) and non-planning impulsiveness (lack of orientation to the future). Each item is measured on a 4-point Likert scale ranging from "rarely/never" to "almost always/always". The total score is obtained by summing all the item ratings, offering a possible range from 30 to 120, with higher scores indicating greater impulsivity. In our population, the BIS-11 displayed good internal consistency (Cronbach's α = 0.78). However, the three subscales had relatively low reliability with Cronbach's α coefficients of 0.58 for the attentional subscale, 0.57 for the motor subscale, and 0.64 for the non-planning subscale. Moreover, confirmatory factor analysis revealed a weak 3-dimension structure of the BIS-11 in our data (Standardized Root-Mean square Residual (SRMR) = 0.07, Adjusted Goodness-of-Fit Index (AGFI) = 0.88, Normed-Fit Index (NFI) = 0.70). Therefore, we only considered the total BIS-11 score in the present study. We divided this score into 3 different categories according to the clinical thresholds proposed by Stanford et al. [START_REF] Stanford | Fifty years of the Barratt Impulsiveness Scale: An update and review[END_REF]. Subjects with a BIS-11 total score >71 were considered highly impulsive, those between 52 and 71 were in the average range of impulsivity, and those <52 were defined as over-controlled.

Anthropometry

Self-reported height and weight data were collected each year using a web-based questionnaire. Closest available data after the date of completion of the BIS-11 were used. BMI (kg/m 2 ) was calculated as the ratio of weight to squared height. According to WHO reference values [START_REF] Health Organization | Obesity: Preventing and managing the global epidemic. Report of a WHO consultation[END_REF], participants were classified into four different weight statuses following their BMI: underweight (BMI < 18.5), normal (18.5 ≤ BMI < 25), overweight (25 ≤ BMI < 30), and obese (BMI ≥ 30). Obese individuals were further classified into three obese categories: obese class I (30 ≤ BMI < 35), obese class II (35 ≤ BMI < 40) and obese class III (BMI ≥ 40).

Covariates

Potential confounders of the relationship between impulsivity and weight status identified based on the literature were considered: age (18-24 years, 25-39 years, 40-54 years, 55-64 years, ≥65 years) [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF], education level (primary, secondary, university) [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF], smoking status (never smoker, former smoker or current smoker) [START_REF] Granö | Impulsivity as a predictor of smoking and alcohol consumption[END_REF], alcohol intake (g/day) [START_REF] Granö | Impulsivity as a predictor of smoking and alcohol consumption[END_REF], physical activity [START_REF] Joseph | The neurocognitive connection between physical activity and eating behaviour[END_REF], occupational status (unemployed, student, self-employed and farmer, employee and manual worker, managerial staff and intellectual profession, intermediate professions, retired) [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF], monthly income per household unit [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF], matrimonial status (living alone, living with a partner, married, divorced or separated or widowed [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF]. Physical activity was assessed with a short form of the French version of the International Physical Activity Questionnaire (IPAQ) [START_REF] Craig | International physical activity questionnaire: 12-country reliability and validity[END_REF]. Weekly energy expenditure expressed in Metabolic Equivalent of Task (MET-minutes/week) was estimated and three levels of physical activity were constituted (low (<30 min/day), moderate (30-60 min/day), and high (≥60 min/day)). Monthly income per household unit was calculated with information about household income and composition. The number of people of the household was converted into a number of consumption units (CU) according to a weighting system: one CU is attributed for the first adult in the household, 0.5 for other persons aged 14 or older and 0.3 for children under 14 [34]. Categories of income were defined as followed: <900, 900-1200, 1200-1800, 1800-2300, 2300-2700, 2700-3700, and >3700 euros per household unit as well as "unwilling to answer".

Statistical Analyses

Subjects' characteristics were compared across gender with Student's t-tests for continuous variables and chi-square tests for categorical variables. Since the test for the proportional odds assumption was significant (p < 0.0001), multinomial logistic regression analyses were performed to assess the association between impulsivity categories and BMI categories (as a 4-level dependent variable with normal weight category as reference). An additional analysis was performed on the three obese categories. The strength of the association was determined by calculating odds ratios (ORs) and 95% confidence intervals (CI). An interaction between impulsivity and gender was examined in the multinomial logistic model. Since this interaction was significant (p < 0.0001), all models were stratified by gender. Two models were tested: a model without adjustment and a model adjusted on covariates. The adjusted model included the following variables: age, education level, smoking status, alcohol intake, physical activity, employment status, monthly income per household unit and matrimonial status. Missing data on covariates were imputed using multiple imputation. The Hochberg method was applied to correct for multiple testing. All tests of statistical significance were 2-sided and significance was set at 5%. Statistical analyses were performed using SAS software (version 9.3, SAS Institute Inc., Cary, NC, USA).

Results

Characteristics of the Sample

A total of 51,394 subjects (41%) from the NutriNet-Santé cohort completed the optional BIS-11 questionnaire, from the 125,377 subjects who received it. Among them, 73 participants were excluded because of missing data on weight or height, 15 participants because they presented an acquiescence bias (agreeing to all questions without consideration of reversed items) in answers of the BIS-11, and 263 because they were pregnant, leaving 51,043 participants (11,929 men and 39,114 women) in the final data set. Compared with excluded participants, included participants were older (50.5 years for included participants vs. 42.8 years for excluded participants, p < 0.0001), had a higher proportion of men (23.4% vs. 21.8%, p < 0.0001) and a higher proportion of individuals with university education (64.2% vs. 58.8%, p < 0.0001). The proportion of overweight participants (excluding obesity) was higher (23.2 vs. 21.4%, p < 0.0001), while the proportion of obese was lower (9.4% vs. 11.5%, p < 0.0001). The percentage of underweight was equal across samples (5.0% vs. 5.2%, p = 0.068).

Table 1 shows characteristics of the sample according to gender. Overall, women were younger, had better level of education, more often had never been a smoker, drank less alcohol, had a better level of physical activity, were more active, had lower levels of income in their household, were less often married, and were less overweight compared to men. Women were also found to be significantly more impulsive than men on average, even when adjusting for potential confounders (57.5 for men vs. 59.1 for women). 3 The household income per month was calculated by consumption units (CU). The number of people of the household was converted into a number of CU according to a weighting system: one CU is attributed for the first adult in the household, 0.5 for other persons aged 14 or older and 0.3 for children under 14 [34]; 4 The test was performed for underweight, normal, overweight and global obesity categories.

Socio-Demographic, Economic and Lifestyle Factors According to the Level of Impulsivity

Table 2 shows individual characteristics according to the BIS-11 total score and the BIS-11 categories. Mean of the BIS-11 total score for the whole sample was 58.7 (SD = 8.0, range = 31-102). Highly impulsive subjects represented 6.3% of the sample, whereas over-controlled subjects represented 17.8% of the sample. The percentage of highly impulsive subjects was high in younger participants, in women, in participants with a lower level of education, in current smokers, in participants with a low level of physical activity, in unemployed subjects or student, in participants with a low monthly income per household unit and in participants living alone. Moreover, highly impulsive respondents had the highest consumption of alcohol. The percentage of highly impulsive subjects increased with level of overweight/obesity and was highest in class III obesity. Percentage of over-controlled subjects was higher in underweight and normal-weight subjects than in overweight/obese respondents. 3 The household income per month was calculated by consumption units (CU). The number of people of the household was converted into a number of CU according to a weighting system: one CU is attributed for the first adult in the household, 0.5 for other persons aged 14 or older and 0.3 for children under 14 [34]; 4 The tests were performed for underweight, normal, overweight and global obesity categories.

Association between Impulsivity and BMI Categories According to Gender

We observed a significant interaction between gender and impulsivity (p < 0.0001). Results of the positive association between impulsivity and BMI stratified by gender are shown in Table 3. In both genders, individuals with high impulsivity level (total BIS-11 score >71) were more likely to be obese. Impulsive men were also more likely to be overweight. The highest OR were observed for class III obesity. For highly impulsive women, associations between impulsivity and the 3 classes of obesity were non-significant. Associations between over-control and weight status were all non-significant.

Discussion

This population-based study showed that impulsive men were more likely to be overweight and obese and impulsive women were more likely to be obese compared to participants with an average level of impulsivity. These associations were particularly strong for obesity and more specifically for class III obesity in men. Women were more impulsive than men, but the association between impulsivity and weight status was stronger in men.

Level of Impulsivity According to Socio-Demographic, Economic and Lifestyle Characteristics

The average score of the BIS-11 in our study was consistent with previous studies [START_REF] Stanford | Fifty years of the Barratt Impulsiveness Scale: An update and review[END_REF][START_REF] Reise | The Barratt Impulsiveness Scale-11: Reassessment of its structure in a community sample[END_REF]. In agreement with the literature, higher levels of impulsivity were observed in younger participants, [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF] low-educated subjects [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF], smokers [START_REF] Granö | Impulsivity as a predictor of smoking and alcohol consumption[END_REF], higher alcohol drinkers [START_REF] Granö | Impulsivity as a predictor of smoking and alcohol consumption[END_REF], unemployed subjects and students [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF], participants with low income [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF] and in participants living alone [START_REF] Chamorro | Impulsivity in the general population: A national study[END_REF]. Higher levels of impulsivity were also found in subjects with lower physical activity, but the difference was small. Finally, women had significantly greater scores of impulsivity than men, contrasting with previous data showing no differences in impulsivity measured by the BIS-11 according to gender [START_REF] Patton | Factor structure of the Barratt impulsiveness scale[END_REF][START_REF] Dietrich | Body weight status, eating behavior, sensitivity to reward/punishment, and gender: Relationships and interdependencies[END_REF][START_REF] Stanford | Fifty years of the Barratt Impulsiveness Scale: An update and review[END_REF][START_REF] Jasinska | Impulsivity and inhibitory control deficits are associated with unhealthy eating in young adults[END_REF]. A meta-analysis [START_REF] Cross | Sex differences in impulsivity: A meta-analysis[END_REF] found slightly higher levels of impulsivity in men using the BIS-11. However, differences in impulsivity according to gender varied depending on the measure of impulsivity or the factor that was studied.

Association between Impulsivity Levels and Weight Status

In agreement with our study, impulsivity measured by the BIS-11 was lower in a healthy weight group compared with an overweight group without taking into account potential confounders [START_REF] Babbs | Decreased caudate response to milkshake is associated with higher body mass index and greater impulsivity[END_REF]. However, another study found no difference in impulsivity between obese and normal weight subjects [START_REF] Loeber | Impairment of inhibitory control in response to food-associated cues and attentional bias of obese participants and normal-weight controls[END_REF]. Other studies reporting correlation coefficients between the BIS-11 (or a short version of the BIS-11) and BMI showed either non-statistically significant correlations [START_REF] Dietrich | Body weight status, eating behavior, sensitivity to reward/punishment, and gender: Relationships and interdependencies[END_REF][START_REF] Van Koningsbruggen | Successful restrained eating and trait impulsiveness[END_REF] or weak correlations [START_REF] Meule | Facets of impulsivity interactively predict body fat and binge eating in young women[END_REF][START_REF] Davis | Attention-deficit/hyperactivity disorder: Associations with overeating and obesity[END_REF][START_REF] Meule | Impulsivity and overeating: A closer look at the subscales of the Barratt Impulsiveness Scale[END_REF]. It must be noted that these studies [START_REF] Dietrich | Body weight status, eating behavior, sensitivity to reward/punishment, and gender: Relationships and interdependencies[END_REF][START_REF] Van Koningsbruggen | Successful restrained eating and trait impulsiveness[END_REF][START_REF] Meule | Facets of impulsivity interactively predict body fat and binge eating in young women[END_REF][START_REF] Davis | Attention-deficit/hyperactivity disorder: Associations with overeating and obesity[END_REF][START_REF] Meule | Impulsivity and overeating: A closer look at the subscales of the Barratt Impulsiveness Scale[END_REF] were performed on specific populations (generally women and/or students) with a lack of heterogeneity which could alter the association. Studies using other measures of impulsivity, including self-reported personality trait questionnaires [START_REF] Rydén | Severe obesity and personality: A comparative controlled study of personality traits[END_REF][START_REF] Davis | Sensitivity to reward and body mass index (BMI): Evidence for a non-linear relationship[END_REF][START_REF] Mobbs | Obesity and the four facets of impulsivity[END_REF][START_REF] Gerlach | Personality traits and obesity: A systematic review[END_REF][START_REF] Terracciano | Facets of personality linked to underweight and overweight[END_REF], and behavioral measures, such as response inhibition [START_REF] Nederkoorn | Impulsivity in obese women[END_REF] or delay discounting [START_REF] Jarmolowicz | Robust relation between temporal discounting rates and body mass[END_REF][START_REF] Amlung | Steep discounting of delayed monetary and food rewards in obesity: A meta-analysis[END_REF], found positive associations between impulsivity and weight status.

Impulsivity could indicate a lack of consideration about health consequences when choosing food. Impulsive individuals with a high reward sensitivity will rather favor present benefit and consume foods that give them pleasure [START_REF] Dawe | Reward drive and rash impulsiveness as dimensions of impulsivity: Implications for substance misuse[END_REF]. In the literature, impulsive behavior was linked to overeating and preference for sweet and fatty foods [START_REF] Davis | From motivation to behaviour: A model of reward sensitivity, overeating, and food preferences in the risk profile for obesity[END_REF][START_REF] Mullan | Self-regulation and the intention behaviour gap. Exploring dietary behaviours in university students[END_REF][START_REF] Garza | Impulsivity and fast-food consumption: A cross-sectional study among working adults[END_REF], which could lead to weight gain over time. Impulsivity was related to other eating-behavior facets, for instance emotional eating and external eating [START_REF] Hou | External eating, impulsivity and attentional bias to food cues[END_REF][START_REF] Ebneter | Impulsivity in restrained eaters: Emotional and external eating are associated with attentional and motor impulsivity[END_REF], and mood before eating [START_REF] Nasser | Impulsivity and test meal intake in obese binge eating women[END_REF]. Impulsive individuals also tend to exhibit pathological eating behaviors such as binge eating [START_REF] Racine | The possible influence of impulsivity and dietary restraint on associations between serotonin genes and binge eating[END_REF], addictive-like consumption of food [START_REF] Murphy | Interrelationships among impulsive personality traits, food addiction, and Body Mass Index[END_REF], and other eating disorders [START_REF] Rosval | Impulsivity in women with eating disorders: Problem of response inhibition, planning, or attention?[END_REF][START_REF] Galanti | Test meal intake in obese binge eaters in relation to impulsivity and compulsivity[END_REF] more often than non-impulsive ones. Impulsive eaters with high dietary restraint were shown to overeat more than non-impulsive high-restrained eaters [START_REF] Jansen | High-restrained eaters only overeat when they are also impulsive[END_REF], while another study found no interaction between dietary restraint and impulsivity [START_REF] Price | Self-reported eating traits: Underlying components of food responsivity and dietary restriction are positively related to BMI[END_REF]. Food reward responsivity (FFR) predicted a higher BMI among impulsive individuals compared with non-impulsive individuals [START_REF] Price | Self-reported eating traits: Underlying components of food responsivity and dietary restriction are positively related to BMI[END_REF]. Finally, specific interactions with reward sensitivity, inhibitory control and emotion regulation interactions might also occur [START_REF] Dietrich | Body weight status, eating behavior, sensitivity to reward/punishment, and gender: Relationships and interdependencies[END_REF][START_REF] Dawe | Reward drive and rash impulsiveness as dimensions of impulsivity: Implications for substance misuse[END_REF]. These data suggest that impulsive behavior could therefore lead to difficulties in control of food intake and weight management.

In the present study, impulsivity was shown to be strongly associated with severe obesity in men, whereas the association was moderate with overweight. Interestingly, a high prevalence of attention deficit hyperactivity disorder (ADHD)-a disorder characterized by impulsive behavior [START_REF] Davis | Attention-deficit/hyperactivity disorder: Associations with overeating and obesity[END_REF]-was reported among people of extreme obesity [START_REF] Altfas | Prevalence of attention deficit/hyperactivity disorder among adults in obesity treatment[END_REF][START_REF] Agranat-Meged | Childhood obesity and attention deficit/hyperactivity disorder: A newly described comorbidity in obese hospitalized children[END_REF]. ADHD has good correlation with the BIS-11 and is often linked to overeating and overweight [START_REF] Davis | Associations among overeating, overweight, and attention deficit/hyperactivity disorder: A structural equation modelling approach[END_REF].

We cannot exclude potential reverse or bi-directional associations. Indeed, weight gain has also been associated to a change in personality and more specifically an increase in impulsivity [START_REF] Sutin | I know not to, but I can't help it: Weight gain and changes in impulsivity-related personality traits[END_REF], which could be another explanation for the higher proportion of severely obese men among highly impulsive ones compared with other weight status.

We found no association between an over-controlled personality and weight status. This result differed from a previous study, which found a protective impact of a high level of "conscientiousness" on weight gain [START_REF] Gerlach | Personality traits and obesity: A systematic review[END_REF]. Gerlach defined conscientiousness as a "measure of regulation of internal urges and self-discipline", which may be a "potential source of control over impulsive reward-oriented behavior" [START_REF] Gerlach | Personality traits and obesity: A systematic review[END_REF]. Another study found a similar result with impulsivity measured with the Revised NEO Personality Inventory, where low impulsiveness was a predictor of underweight three years after the personality assessment [START_REF] Terracciano | Facets of personality linked to underweight and overweight[END_REF]. These findings suggest that an over-controlled behavior may lead to over-controlled food consumption, leading, in some cases, to underweight. Even though the associations between high impulsivity and underweight were non-significant in our study, results tended to indicate higher odds of being underweight for impulsive participants.

Gender Differences

Men were more likely to be overweight or obese than women when they were highly impulsive. To our knowledge, only one study assessed the association between the BIS-11 and weight status stratified by gender. It found an association with BMI in women whereas no association was found in men [START_REF] Bauer | GABRA2 genotype, impulsivity, and body mass[END_REF]. Gender was shown to modify the association between psychoticism and extraversion personality dimensions, which are closely linked to impulsivity and weight status [START_REF] Faith | Gender differences in the relationship between personality dimensions and relative body weight[END_REF]. Our data showed stronger associations for severe obesity in both genders, even though these associations were non-significant for women after correction for multiple testing, suggesting a weaker and maybe different relationship with impulsivity. Women generally have a higher concern for their body shape and weight control compared to men, which could inhibit impulsive behaviors towards food. Finally, gender was shown to modify the association between weight status and eating behaviors related to impulsivity such as disinhibition [START_REF] Provencher | Eating behaviors and indexes of body composition in men and women from the Québec family study[END_REF], external eating [START_REF] Elfhag | Personality traits and eating behavior in the obese: Poor self-control in emotional and external eating but personality assets in restrained eating[END_REF] and emotional eating [START_REF] Elfhag | Personality traits and eating behavior in the obese: Poor self-control in emotional and external eating but personality assets in restrained eating[END_REF][START_REF] Péneau | Sex and dieting modify the association between emotional eating and weight status[END_REF]. Higher cognitive dietary restraint in women [START_REF] Provencher | Eating behaviors and indexes of body composition in men and women from the Québec family study[END_REF] could also explain the weaker relationship between impulsivity and weight status in women. These results emphasize the importance of considering gender when assessing the association between personality traits or behavior and weight status and in prevention strategies.

Strengths and Limitations

The main strength of this study is its large sample size with subjects of various socio-demographic characteristics and nutritional status, which allows the use of multiple covariates to adjust for confounding factors and confers a great statistical power to detect significant differences among several classes of weight status. This study brings information about the importance of socio-demographic, economic and lifestyle confounding factors, which have rarely been studied when evaluating the association between impulsivity and nutritional status. However, we cannot rule out the possibility that other important confounders, such as individual or environmental factors, were not taken into account. To our knowledge, few studies assessed the association between impulsivity and weight status in men and women separately. One limitation of our study is its cross-sectional design, which does not allow us to assess causality. Another limit is the self-reported anthropometric measures, which could have led to misclassification. However, standardized clinical measurements on a subsample (n = 2513) of the NutriNet-Santé cohort showed a good convergence with self-reported data [START_REF] Lassale | Validity of web-based self-reported weight and height: Results of the Nutrinet-Santé study[END_REF]. Our study could also present a selection bias because of the method used to recruit participants, which was based on volunteering. Consequently, our subjects may have high health awareness compared to the global population, and may not be representative of the French population. Considering the multidimensionality of impulsivity as a construct and its various methods of measurement, caution is needed when interpreting and extrapolating our results. The BIS-11 questionnaire is one of the most used self-report measures of impulsivity even though its three subtraits have rarely been explored [START_REF] Stanford | Fifty years of the Barratt Impulsiveness Scale: An update and review[END_REF]. In our sample, two out of the three BIS-11 subscales showed insufficient internal consistency, suggesting a low reliability of the questionnaire in our sample in the assessment of impulsivity. However, several studies showed similar issues [START_REF] Reise | The Barratt Impulsiveness Scale-11: Reassessment of its structure in a community sample[END_REF][START_REF] Haden | Trait impulsivity in a forensic inpatient sample: An evaluation of the Barratt Impulsiveness Scale[END_REF]. Finally, the presence of subjects with psychiatric (e.g., bipolar) or psychological disorders could introduce a bias in our analysis since they have not been excluded [START_REF] Stanford | Fifty years of the Barratt Impulsiveness Scale: An update and review[END_REF].

Conclusions

These results showed an association between high levels of impulsivity measured by the BIS-11 and weight status, where highly impulsive participants were more likely to be overweight or obese. The strongest associations were found in men and with severe obesity. These findings underline disparities regarding these associations according to gender and weight status, suggesting that the mechanisms of the relationship between weight status and impulsivity could be different for men and women. Future studies should investigate gender differences and take them into account when assessing the relationship between impulsivity and weight status. Our results support the need to consider individual personality traits and characteristics in overweight/obesity prevention and treatment. Strategies such as inhibitory control training or attentional bias modification protocols could represent a way to reduce impulsive behaviors toward food.

Table 1 .

 1 Individual characteristics of 51,043 participants of the NutriNet-Santé study (2014), according to gender.

	Variables	All (n

= 51,043) Men (n = 11,929) Women (n = 39,144) p 1

	Age (years) 2	50.5 (14.6)	55.9 (14.1)	48.8 (14.3)	<0.0001
	Age categories (%)				<0.0001
	(18-24)	3.2	1.5	3.8
	(25-39)	23.3	14.8	25.8
	(40-54)	28.8	19.7	30.2
	(55-64)	24.8	23.3	24.8
	65+	19.9	40.6	15.4
	Education level (%)				<0.0001
	Primary	2.5	3.1	2.3
	Secondary	30.1	32.4	29.4
	University	67.2	64.4	68.1
	Missing data	0.2	0.1	0.2
	Smoking status (%)				<0.0001
	Never smoker	50.8	41.5	53.6
	Former smoker	36.0	46.5	32.8
	Current smoker	13.2	12.0	13.5
	Missing data	<0.1	0.0	<0.1
	Alcohol intake (g/day) 2	7.0 (9.9)	12.6 (14.0)	5.3 (7.4)	<0.0001

Table 1 .

 1 Cont.

	Variables	All (n = 51,043)	Men (n = 11,929)	Women (n = 39,144)	p 1
	Physical activity (%)				<0.0001
	Low	35.5	44.7	32.6
	Moderate	41.7	35.8	43.4
	High	22.7	19.3	23.8
	Missing data	0.2	0.1	0.2
	Occupational status (%)				<0.0001
	Unemployed	9.6	4.4	11.2
	Student	2.8	1.3	3.2
	Self-employed, farmer	2.0	2.3	1.9
	Employee, manual worker	15.4	8.2	17.7
	Managerial staff, intellectual profession	23.5	26.3	22.7
	Intermediate professions	15.9	10.7	17.5
	Retired	30.8	46.9	25.9
	Missing data	<0.1	<0.1	<0.1
	Monthly income per household unit (%) 3				<0.0001
	Less than 900 €	7.1	4.7	7.8
	Between 900 € and 1200 €	4.6	3.4	4.9
	Between 1200 € and 1800 €	21.4	19.7	22.0
	Between 1800 € and 2300 €	15.0	14.1	15.3
	Between 2300 € and 2700 €	10.0	11.3	9.6
	Between 2700 € and 3700 €	16.9	20.3	15.8
	More than 3700 €	12.2	17.4	10.6
	Unwilling to answer	12.2	8.8	13.2
	Missing data	0.7	0.3	0.8
	Matrimonial status (%)				<0.0001
	Living alone	13.9	10.7	14.9
	Living with a partner	20.6	16.8	21.7
	Married	53.5	63.9	50.3
	Divorced, separated, widowed	12.0	8.4	13.1
	Missing data	0.1	0.2	0.1
	BMI (kg/m 2 ) 2	24.0 (4.5)	25.1 (3.8)	23.6 (4.7)	<0.0001
	Nutritional status (%)				<0.0001 4
	Underweight (<18.5 kg/m 2 )	5.0	1.0	6.2
	Normal (18.5-24.99 kg/m 2 )	62.4	54.2	64.9
	Overweight (25-29.99 kg/m 2 )	23.2	35.1	19.6
	Obese (≥30 kg/m 2 )	9.4	9.7	9.3
	Obese Class I (30-34.99 kg/m 2 )	6.5	7.5	6.2
	Obese Class II (35-39.99 kg/m 2 )	2.0	1.6	2.2
	Obese Class III (≥40 kg/m 2 )	0.9	0.6	0.9
	BIS-11 total score 2	58.7 (8.0)	57.6 (8.0)	59.1 (8.0)	<0.0001
	Boldface indicates statistical significance;

1

Adjusted p values for multiple comparisons (Hochberg method) based on the Student's t test and Pearson χ 2 test, as appropriate; 2 Mean (SD);

Table 2 .

 2 Individual characteristics of 51,043 participants of the NutriNet-Santé study (2014), according to the BIS-11 total score and its categories, according to gender.

		Whole Sample			Men (n = 11,929)				Women (n = 39,144)
	Variables	BIS-11 Mean	p 1	Over-Control	Average Impulsivity	High Impulsivity	p 1	Over-Control	Average Impulsivity	High Impulsivity	p 1
		(SD)		(n = 2641)	(n = 8691)	(n = 597)		(n = 6460)	(n = 30,051)	(n = 2603)
	Age (years) 2			55.8 (13.5)	55.9 (14.3)	55.8 (14.6)	0.959	49.0 (13.8)	48.9 (14.3)	48.3 (15.2)	0.18
	Age categories (%)		<0.0001				0.02				<0.0001
	(18-24)	60.8 (8.4)		16.6	74.3	9.1		11.4	78.1	10.6
	(25-39)	58.8 (7.9)		20.6	74.9	4.5		17.0	76.5	6.6
	(40-54)	58.5 (8.0)		23.9	71.1	5.0		17.1	76.6	6.2
	(55-64)	58.7 (7.9)		23.1	72.2	4.7		16.3	77.4	6.4
	65+	58.8 (8.2)		21.2	73.6	5.3		16.3	76.6	7.1
	Education (%)		<0.0001				<0.0001				<0.0001
	Primary	61.5 (8.7)		17.3	70.5	12.2		8.8	77.0	14.1
	Secondary	59.8 (8.3)		19.1	74.2	6.7		14.0	77.0	9.1
	University	58.2 (7.6)		23.9	72.3	3.8		17.9	76.8	5.4
	Smoking status (%)		<0.0001				<0.0001				<0.0001
	Never smoker	57.8 (7.8)		26.6	70.1	3.3		19.1	75.9	5.1
	Former smoker	59.3 (8.0)		19.9	74.5	5.6		14.4	77.8	7.7
	Current smoker	60.8 (8.3)		15.6	75.9	8.6		11.5	78.1	10.4
	Alcohol intake (g/day) 2			10.9 (12.9)	13.0 (14.1)	14.5 (15.8)	<0.0001	4.5 (6.7)	5.3 (7.4)	6.6 (9.4)	<0.0001
	Physical activity (%)		<0.0001				0.026				<0.0001
	Low	59.3 (8.2)		21.7	72.3	6.0		15.7	76.7	7.7
	Moderate	58.7 (7.9)		20.9	74.2	4.9		16.2	77.7	6.2
	High	58.4 (8.0)		23.4	72.0	4.6		17.6	75.9	6.5
	Occupational status (%)		<0.0001				<0.0001				<0.0001
	Unemployed	60.9 (8.6)		14.0	76.3	9.7		12.2	76.5	11.3
	Student	60.9 (8.6)		10.7	78.7	10.7		13.4	74.9	11.7
	Self-employed, farmer	59.4 (8.0)		21.0	73.1	5.9		13.0	79.5	7.5
	Employee, manual worker	59.7 (8.0)		17.1	75.5	7.4		14.7	77.7	7.6
	Managerial staff, intellectual profession	57.3 (7.5)		26.9	70.5	2.6		20.2	75.8	4.1
	Intermediate professions	58.3 (7.7)		21.0	73.2	5.7		17.8	77.0	5.3
	Retired	58.7 (8.0)		21.7	73.2	5.1		16.2	77.3	6.5
	Monthly income per household unit (%) 3		<0.0001				<0.0001				<0.0001
	Less than 900 €	61.4 (8.8)		16.6	73.0	10.5		11.0	75.8	13.2
	Between 900 € and 1200 €	59.7 (8.1)		16.8	75.8	7.4		15.0	76.6	8.4
	Between 1200 € and 1800 €	59.4 (8.1)		20.4	73.2	6.4		14.2	78.3	7.5
	Between 1800 € and 2300 €	58.9 (7.8)		20.4	74.1	5.5		16.3	77.4	6.2
	Between 2300 € and 2700 €	58.3 (7.8)		21.0	74.7	4.3		18.1	76.5	5.5
	Between 2700 € and 3700 €	57.7 (7.6)		24.4	71.9	3.8		19.0	76.4	4.6
	More than 3700 €	57.3 (7.6)		26.2	70.4	3.4		20.2	75.7	4.1
	Unwilling to answer	58.5 (8.0)		22.6	73.6	3.8		17.7	75.9	6.4

Table 2 .

 2 Cont.

		Whole Sample			Men (n = 11,929)				Women (n = 39,144)
	Variables	BIS-11 Mean	p 1	Over-Control	Average Impulsivity	High Impulsivity	p 1	Over-Control	Average Impulsivity	High Impulsivity	p 1
		(SD)		(n = 2641)	(n = 8691)	(n = 597)		(n = 6460)	(n = 30,051)	(n = 2603)
	Matrimonial status (%)		<0.0001				<0.0001				<0.0001
	Living alone	60.2 (8.4)		18.4	73.5	8.1		13.0	77.2	9.8
	Living with a partner	59.3 (7.9)		19.1	73.9	7.1		14.5	78.3	7.2
	Married	57.9 (7.8)		24.0	71.9	4.1		19.0	75.8	5.2
	Divorced, separated, widowed	59.7 (8.2)		19.1	73.9	7.1		14.4	77.7	7.9
	BMI (kg/m 2 ) 2			24.8 (3.6)	25.2 (3.8)	26.3 (4.6)	<0.0001	23.4 (4.5)	23.7 (4.6)	24.3 (5.3)	<0.0001
	Nutritional status (%)		<0.0001 4				<0.0001 4				<0.0001 4
	Underweight (<18.5 kg/m 2 )	58.8 (8.4)		21.3	69.7	9.0		18.7	74.3	7.0
	Normal (18.5-24.99 kg/m 2 )	58.5 (7.9)		23.5	72.6	3.9		16.9	77.0	6.0
	Overweight (25-29.99 kg/m 2 )	58.9 (8.1)		21.4	72.9	5.7		15.4	77.3	7.3
	Obese (≥30 kg/m 2 )	60.0 (8.5)		17.1	74.4	8.5		14.4	76.2	9.4
	Obese Class I (30-34.99 kg/m 2 )	59.8 (8.3)		17.1	74.8	8.1		14.2	76.9	8.9
	Obese Class II (35-39.99 kg/m 2 )	60.3 (8.6)		17.7	75.3	7.0		15.1	75.0	9.9
	Obese Class III (≥40 kg/m 2 )	60.8 (9.1)		15.1	67.1	17.8		13.9	74.4	11.7

Boldface indicates statistical significance;

1

Adjusted p values for multiple comparisons (Hochberg method) based on the Student's t test and Pearson χ 2 test, as appropriate; 2 Mean (SD);

Table 3 .

 3 Multinomial logistic regression analyses showing the association between BIS-11 levels and BMI categories (with normal weight category as reference), according to gender in 51,043 participants of the NutriNet-Santé study (2014).

		Over-Control (<52)	Average Impulsivity (52-71)	High Impulsivity (>71)
		OR (95% CI)	p 1		OR (95% CI)	p 1
	Men (n = 11,929)
	Raw model 2
	Underweight	0.94 (0.61, 1.47)	0.80	Reference	2.44 (1.29, 4.63)	0.07
	Overweight	0.91 (0.83, 1.00)	0.30	Reference	1.47 (1.23, 1.77)	0.0006
	Obese	0.86 (0.78, 0.95) 0.0008	Reference	1.58 (1.40, 1.79) <0.0001
	Obese Class I	0.71 (0.59, 0.85) 0.003	Reference	2.05 (1.56, 2.69) <0.0001
	Obese Class II	0.73 (0.50, 1.07)	0.52	Reference	1.75 (0.98, 3.14)	0.36
	Obese Class III	0.69 (0.36, 1.34)	0.70	Reference	5.00 (2.68, 9.34) <0.0001
	Adjusted model 2,3
	Underweight	1.05 (0.67, 1.66)	0.90	Reference	1.80 (0.92, 3.51)	0.90
	Overweight	0.97 (0.87, 1.06)	0.90	Reference	1.40 (1.16, 1.70)	0.01
	Obese	0.80 (0.67, 0.95)	0.16	Reference	1.80 (1.39, 2.33)	0.0002
	Obese Class I	0.79 (0.66, 0.96)	0.25	Reference	1.74 (1.31, 2.31)	0.0028
	Obese Class II	0.82 (0.55, 1.21)	0.90	Reference	1.42 (0.78, 2.58)	0.90
	Obese Class III	0.81 (0.42, 1.57)	0.90	Reference	3.57 (1.86, 6.85)	0.0028
	Women (n = 39,144)
	Raw model 2
	Underweight	1.15 (1.03, 1.28)	0.13	Reference	1.21 (1.02, 1.43)	0.20
	Overweight	0.91 (0.85, 0.98)	0.08	Reference	1.21 (1.09, 1.34)	0.003
	Obese	0.71 (0.60, 0.84) 0.031	Reference	2.17 (1.70, 2.77) <0.0001
	Obese Class I	0.84 (0.75, 0.95) 0.052	Reference	1.48 (1.28, 1.72) <0.0001
	Obese Class II	0.91 (0.75, 1.11)	0.70	Reference	1.69 (1.34, 2.13)	0.0002
	Obese Class III	0.85 (0.63, 1.15)	0.70	Reference	2.00 (1.44, 2.79)	0.0006
	Adjusted model 2,3
	Underweight	1.17 (1.05, 1.31) 0.092	Reference	1.12 (0.95, 1.33)	0.90
	Overweight	0.95 (0.88, 1.02)	0.90	Reference	1.13 (1.02, 1.25)	0.31
	Obese	0.95 (0.86, 1.05)	0.90	Reference	1.30 (1.15, 1.48)	0.0013
	Obese Class I	0.92 (0.81, 1.04)	0.90	Reference	1.26 (1.08, 1.47)	0.058
	Obese Class II	1.04 (0.85, 1.26)	0.90	Reference	1.34 (1.05, 1.70)	0.25
	Obese Class III	0.98 (0.72, 1.33)	0.90	Reference	1.48 (1.05, 2.08)	0.90
	Boldface indicates statistical significance; 1 Adjusted p values for multiple comparisons (Hochberg method); 2 BMI
	categories are defined as follow: underweight (<18.5 kg/m 2 ), overweight (25-29.99 kg/m 2 ), Obese (≥30 kg/m 2 ),
	(obese Class I (30-34.99 kg/m 2 ), obese Class II (35-39.99 kg/m 2 ), and obese Class III (≥40 kg/m 2 ); 3 Adjusted for
	age, education level, smoking status, daily alcohol intake, physical activity, employment status, monthly household
	income, and matrimonial status.

Acknowledgments:

We thank all the scientists, dietitians, technicians and assistants who helped carry out the NutriNet-Santé study. We especially thank the computer scientists Younes Esseddik, Yasmina Chelgoum, Mohand Ait Oufella, Paul Flanzy and Thi Hong Van Duong; the statisticians Veronique Gourlet, Charlie Ménard, Fabien Szabo, Nathalie Arnault, Laurent Bourhis and Stephen Besseau. We are grateful to the volunteers of the NutriNet-Santé study. The NutriNet-Santé Study is supported by the French Ministry of Health (DGS), the French Institute for Public Health Surveillance (InVS), the French National Institute for Health and Medical Research (INSERM), the French National Institute for Agricultural Research (INRA), the National Conservatory for Arts and Crafts (CNAM), the Medical Research Foundation (FRM), the National Institute for Prevention and Health Education (INPES) and the University of Paris 13. This research was part of the FOODPOL project, which was supported by the French National Institute for Agricultural Research (Institut National de la Recherche Agronomique) in the context of the 2013-2017 Metaprogramme "Diet impacts and determinants: Interactions and Transitions".

Author Contributions: M.B. conducted the literature review and drafted the manuscript. M.B. performed analyses. M.B., G.M.C., F.E., C.M., F.B., G.R., S.H. and S.P. were involved in interpreting results and critically reviewed the manuscript. C.M., S.H. and S.P. were responsible for developing the design and protocol of the study. All authors read and approved the final manuscript.

Conflicts of Interest:

The authors declare no conflict of interest.