Accepted for publication cite as: Nago E, Lachat C, Dossa R, Kolsteren P (2011) Association of out-of-home eating with anthropometric changes: a systematic review of prospective studies. Critical Reviews in Food Science and Nutrition doi 10.1080/10408398.2011.627095 Association of out-of-home eating with anthropometric changes: a systematic review of prospective studies Eunice S Nago1,2, Carl K Lachat2,3, Romain AM Dossa1 and Patrick W Kolsteren2,3,* 1 Department of Nutrition and Food Sciences, Faculty of Agricultural Sciences, University of Abomey-Calavi, Cotonou, Benin 2 Department of Food Safety and Food Quality, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium 3 Nutrition and Child Health Unit, Department of Public Health, Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium Keywords: Obesity, Life Style, Diet, Out-of-home eating, Prospective Studies Running title: Eating out and anthropometric changes Acknowledgements CKL and PWK were responsible for the development of the search syntax and of the screening methodology. CKL carried out the search. ESN and CKL did the screening and PWK resolved conflicts. RAD assisted in the interpretation of the data. ESN drafted the paper and all authors critically reviewed the manuscript. Corresponding author Patrick W Kolsteren, Nutrition and Child Health Unit, Department of Public Health, Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, Antwerp, Belgium. Tel: 00 32 3 247 63 89 / Fax: 00 32 3 247 65 43 / Email: pkolsteren@itg.be Conflict of interest statement 1 None of the authors declares a conflict of interest. 2 Abbreviations USA: The United States of America US: The United States BMI: Body mass index EPIC-PANACEA: The European Prospective Investigation Into Cancer-Physical activity, Nutrition, Alcohol, Cessation of smoking, eating Out of Home and Obesity study CARDIA: The Coronary Artery Risk Development in young Adults study NR: Not reported WHA: Australian Longitudinal Study on Women’s Health SUN: Seguimiento Universidad de Navarra (University of Navarro Follow-up) SEASONS: Seasonal Variation of Blood Cholesterol Study Add Health: National Longitudinal Study of Adolescent Health. WHO: World Health Organization OH: Out-of-home WC: waist circumference IA: Interview-administered SA: Self-administered EI: Energy intake PA: Physical activity 3 Abstract In the present review, the association of out-of-home eating with anthropometric changes was examined. Peer reviewed studies in 8 databases were searched for and 15 prospective studies were finally included in the review. The quality of the data was assessed by considering the risk of bias in sample selection, data collection methods and the appropriateness of the statistical tests used. From this, 7 studies, which used relatively large samples or had a follow-up period longer than 10 years, were retained for further analysis. It was concluded that eating out-of-home foods frequently increases the risk of becoming overweight or obese, bodyweight, waist circumference and women’s BMI. Increase in weight and waist circumference was greater when eating at fast-food outlets than at restaurants. 4 Introduction Obesity constitutes one of the most serious public health problems nowadays (1). It is a major burden to public health due to its adverse health consequences in the short and the long term. The most significant health-related consequences are cardiovascular diseases, hypertension, diabetes, cancer and osteoporosis (2). Obesity affects various populations, of all age groups and both sexes, in high-income as well as low-and-middle income countries. A fundamental cause of obesity, in addition to the increasingly sedentary lifestyles of today populations, is the change in dietary habits. An important change in food habits is the substantial increase of out-of-home eating all over the world. For instance, three nationwide surveys in the USA showed an increase in the daily energy contribution of out-of-home foods in people older than 2 years from 23 to 36% between 1977 and 1996 (3). In 1994, 56% of the US population ate outside their home at least once a day (4). In a recent study in Benin, foods prepared out-of-home have already been shown to provide 45% of the daily energy intake in a sample of urban adolescents (5). Away-from-home foods are perceived as contributing to the obesity pandemic because of their high energy-density, low nutrient density and large portions sizes (6;7). It has been shown previously that weight gain is induced by an imbalance between energy intake and energy expenditure and is driven by the consumption of foods with a high energy-density and of increased portion sizes (8-10). Several interventions addressing various sources of out-ofhome foods, such as worksites (11;12), schools (13;14)and vending machines (15;16), have been developed with the purpose of improving the nutritional quality of the food offer or manage weight status. These initiatives have encountered a moderate success. To our knowledge the strength of the evidence of the association of out-of-home eating with an increased risk of obesity has not been assessed up to now. It is important to review the available literature on this topic in order to design relevant obesity prevention programs directed towards people who consume food outside their home. There has been a recent review but restricted to fast-foods only (17). The present systematic review aimed at assessing the association of out-of-home eating with anthropometric changes in various population groups, in particular the risk of becoming overweight or obese and increases in bodyweight, BMI, BMI z-score and waist circumference. We report the importance and the nutritional characteristics of out-of-home eating in another review (Lachat C, Nago E, Verstraeten R, Roberfroid D, Van Camp J, Kolsteren P, unpublished data). 5 Methods Inclusion and exclusion criteria Original studies reporting longitudinally at least an anthropometric measure and, longitudinally or not, the energy contribution or the frequency of out-of-home eating, were retained, including interventions targeting dietary modification or weight management. Any definition of out-of-home eating was considered (for instance the definitions using the place of preparation or of consumption of foods) as well as studies which used a single source of out-of-home foods e.g. fast foods or school foods. The review targeted free living humans who were healthy at baseline, without specific dietary requirements, from both sexes, from any age, race or ethnicity and any country. Therefore, studies reporting only on overweight or obese subjects at baseline, pregnant women, or elderly in nursing homes, prisoners and patients were excluded. Papers reporting on food safety and qualitative papers, such as editorials and comments, were not considered. The references of the papers retained for data extraction were also screened to see whether additional papers emerged. The inclusion and exclusion criteria that were used in the screening process are listed in Table 1. Literature Search Studies were identified by searching through 8 electronic databases: Medline, CAB Abstracts, the Cochrane Library, ISI Web of Knowledge, Embase, Agricola, Ingenta and Bioline international. All contents were first assessed, without date and language restriction, from July 7th to July 10th, 2010. There was an update from March 10th to March 18th2011. The search syntax was elaborated in Medline and adapted to the other databases. Combinations of the following terms were searched for in titles or abstracts: out-of-home, eating out, street food, junk food, outside the home, away from home, takeaway, cafeteria, food dispenser, catering, fast food, canteen, restaurant, worksite, food, diet, food habits, eating, nutrition assessment and feeding behavior. All the 7319 papers found were merged into a single database (Reference manager version 9, The Thomson Corporation, NY) and doubles were deleted. A researcher (CL) screened the titles of the remaining papers. The next steps were the reading of abstracts and of full papers by two co-authors (CKL and ESN) independently. In case of doubt at any stage, the paper concerned was kept in the review database. A discussion followed to solve the 6 divergence between the two independent appraisals and when necessary, the expertise of a third co-author (PWK) was requested. A flow chart of the screening is represented in Figure1. Analysis of the papers Information, such as authors and year of publication, countries, participants to the study and sample size, was extracted to present each study included in this review. The baseline characteristics of the subjects, the exposure (quantity, energy intake or frequency of out-of-home eating) and the outcome measures (risk of becoming overweight or obese, changes in bodyweight, BMI, BMI z-score and waist circumference) were also retrieved. Results are presented in terms of change or absence of change in the outcome measure over time, as an effect of a longitudinal change in out-of-home eating or of the consumption or outof-home foods at baseline. The methodological quality of the studies was assessed by considering the risk of bias in the sample selection (representativeness and participation rate), the design (controlled trial or not), the data collection methods (validity and reliability), the appropriateness of the statistical tests and whether they accounted for potential confounders or misreporting of dietary intake. Results Description of the articles of the review Of the 7319 papers, 128 were retained for full text reading. Thirteen papers were kept after full reading and from the screening of their references, 2 additional studies were retrieved. Hence, 15 papers were included in this review (Table 2).Eight studies (18-25) used the place of consumption to define out-of-home eating. Most studies focused on fast-foods (18;19;23;24;26-30). The other type of out-of-home foods that were assessed by the studies were restaurant foods (18-20;22) quick-service and coffee shop foods (31), takeaway foods (30;32) and workplace foods (22). All the papers have been published in the last 13 years. Among the 15 papers, 10 reported studies conducted in the USA (18-21;23;24;27-29;31).One paper (22) analyzed data from the European Prospective Investigation Into Cancer-Physical activity, Nutrition, Alcohol, Cessation of smoking, eating Out of Home and Obesity (EPIC-PANACEA) (33;34) which is carried out in 10 European countries. One study in Australia (32), one in the UK 7 (30), one in Spain (25) and one in Canada (26) were also included in this review. Three papers (18;19;24) analyzed data from the Coronary Artery Risk Development in young Adults (CARDIA) study (35;36). Two other studies (27;28) reported data from the only controlled trial included in the review, the Pound of Prevention Study (37). Subjects were in a large age-range, going from 8 to 75 years and mostly of both sexes. Twelve of the papers reported on adults above 18 years of age (18-22;24-29;32). Eight studies sampled at baseline children and adolescents (23;30;31)and/or young adults (18-20;23;24;32). The sample size at baseline varied from 68 subjects (20) to 36994 subjects (22), with eight studies that can be considered as large studies (18;19;22-25;30;32). The follow-up period reported in the papers was variable and ranged from 12 weeks (20;26) to 15 years (24;30). Four studies followed subjects for more than 10 years (19;24;30;31). Association of eating out-of-home with anthropometric changes Risk of overweight or obesity Eating more often at a place out-of-home, in general, was associated with an increase in the risk of becoming overweight or obese (Table 3).In the paper by Ma et al. (21), the frequency of eating each meal (breakfast, lunch or dinner) out-of-home was calculated by dividing the number of each meal out-of-home by the total number of days on which the meal was consumed. Subjects were then separated into quartiles based on this frequency. Compared to the subjects in the first quartile of breakfast frequency or of dinner frequency away-from-home, the other subjects had about 2 to 3 times more risk of becoming obese. At the opposite, being in the 2nd, 3rd or 4th quartile of lunch frequency out-of-home was associated with a 30-60% lower risk for obesity, compared to being in the first quartile. BesRastrollo et al. (25)followed a larger sample (14106 versus 641 subjects) for a longer period (average follow-up of 4 years versus 1 year) and found a 22 to 33% higher risk of overweight or obesity when eating out at least once a week, compared to not eating out. Change in bodyweight More frequent fast-food consumption increased bodyweight (Table 4). The increase in bodyweight ranged from 0.15 kg over 13 years for an additional eating occasion of fast-food per week (19) to 1.68 kg over 3 years per each additional meal per week at a fast-food establishment (27). Li et al. (29) reported an increase in weight with 1-2 visits/week to fast- 8 foods outlets during 1 year. Bes-Rastrollo et al. (25) found a 12 to 36% higher risk of gaining 2 kg or more per year when eating at fast-food outlets once or more per week. The increase in weight associated with restaurant frequency was smaller than for fastfood frequency (19;22). In the study by Naska et al. (22), there was no significant association between annual weight change and the energy intake of restaurant eaters or the energy intake from restaurant foods. Change in BMI and BMI z-score Results on the link between fast-food consumption and change in BMI were conflicting. Two studies (26;28) found no difference in BMI with increasing fast-food use (Table 5). The first study (26)concluded that change in fast-food consumption over 12weeks was not correlated with BMI change and the second one showed that over a one-year period, eating at fast-food outlets did not change BMI(28).On the other hand, Duffey et al. (18) concluded that a higher fast-food consumption was associated with a greater change in BMI over 3 years. The increase in BMI was 0.20 kg/m2 for each increase in fast-food frequency of 1 time per week and was higher when the interaction of fast-food and restaurant was examined. There was no association between BMI change and restaurant frequency alone (18) but eating takeaway foods increased BMI in women (32). Compared to women who never or rarely ate takeaway foods, those who ate these once a week were 15% less likely to maintain their BMI within a 5%range after 4 years (Table 5). Eating fast-foods, takeaway or quick-service foods twice a week or more at baseline increased the BMI z-score (30;31) whereas a 5-year change in fast-food consumption did not predict BMI z-score at follow-up, controlling for baseline BMI z-score (23), Table 5. Change in waist circumference Findings about waist circumference were also conflicting (Table 6). Li et al. (29) reported more than 1 cm increase in waist circumference with 1 or 2 visits per week to fastfood establishments during one year but Bédard et al. showed that fast-food consumption had no effect on waist circumference over a 12-week period (26). Quality appraisal of the findings The studies reviewed used appropriate methods for data collection but most did not pre-validate the tool used to measure out-of-home eating. Two studies conducted 24-hour 9 dietary recalls (21;22) and one paper used 7-day dietary records (31) to estimate the importance of eating out. The remaining papers used frequency questionnaires. Ten papers (18;19;21-24;26-29) reported that the dietary assessment was carried out by an interviewer and in most papers (18-21;23;24;26-30), the anthropometric variables were measured and not self-reported. In all studies, except three (22;26;32), the assessment of weight status was done with a standard method or a method which validity and reliability had been established previously. However, for the evaluation of the quantity, energy intake or frequency of awayfrom-home foods, only 3 studies (22;25;26) used pre-validated tools. The studies also used appropriate statistical methods and, except for the study by Bédard et al. (26), adjusted for potential confounders when analyzing the association between eating out and weight status. However, none of the papers had a study design that could infer causality. Only 2 papers (27;28) described a controlled trial but gave no details on the randomization process. Furthermore, as the primary objective of this intervention was weight gain prevention and was not related to out-of-home eating, these studies did not compare the association of out-ofhome eating and weight status between treatments and controls. One paper (26) reported a cohort study and the remaining papers were about interrupted time series. Furthermore, most of the studies were to some extent subjected to selection bias. Seven studies used a small or a convenience sample (20;21;26-29;31). Four other studies (18;19;22;24;25) reported on large samples but were restricted to 4 urban areas in the USA, in the framework of the CARDIA study (18;19;24) or University graduates in Spain (25). Furthermore, 3 out of the 4 studies had an average participation rate (<80%). Only the study by Bes-Rastrollo et al. (25) had a high participation rate (95%).The remaining studies (22;23;30;32) had an average participation rate but the report by Naska et al. (22) used a large sample from 9 European countries and the studies by Niemeier et al. (23), Viner and Cole (30) and Ball et al. (32) covered large national samples. Analyzing the risks of bias did not allow a differentiation among the studies. Thus, sample size and follow-up duration were used as criteria to select the best quality studies. Seven papers were subsequently retained among which 3 studies that used large national samples (23;30;32), the EPIC-PANACEA study by Naska et al. (22), 2 papers with a followup period longer than 10 years (19;24) and the study by Bes-Rastrollo et al. (25) which followed a large sample of University graduates. 10 Among these papers, 1 reported on the risk of overweight and obesity (25), 1 on waist circumference (19), 2 on BMI (25;32), 2 on BMI z-score (23;30) and 4 on bodyweight (19;22;24;25). It was concluded that eating frequently at a place out-of-home increases the risk of becoming overweight or obese. The increase was 33% when eating out at least twice a week, compared to not eating out (25).Eating away from home frequently also increases bodyweight but the weight gain was much higher when eating at fast-food outlets than at restaurants (19;22;24). The weight gain was estimated to 129g per year when eating fastfoods at least twice a week (25). A further finding is that eating at fast-food establishments or eating takeaway foods frequently was associated with an increase in BMI (25;32). Particularly, women who consumed takeaway foods once a week were 15% less likely to maintain their BMI within a 5% range after 4 years, compared to those who never or rarely ate them (32). Findings with regard to BMI z-score relate to the change from adolescence to adulthood and were variable. Change in the frequency of fast-food visits from adolescence to young adulthood did not change BMI z-score at young adulthood, controlling for BMI in adolescence (23) whereas eating fast-foods or takeaway meals twice a week or more in adolescence increased BMI zscore by 0.14 to 0.21 unit between 16 and 30 years (30;31). Finally, eating at fast-food establishments was associated with a greater increase in waist circumference over time than eating at restaurant. Each additional visit to fast-food outlets per week increased waist circumference by 0.12 cm over 13 years and for restaurants, it was 0.08cm (19). Discussion The aim of this systematic review was to assess the link between out-of-home eating and anthropometric changes. After a quality appraisal of the 15 prospective studies included, 7 studies, which used relatively large samples (22;23;25;30;32) or had a follow-up period longer than 10 years (19;24), were retained for further conclusions. From these papers, it was concluded that eating frequently at a place out-of-home increases the risk of becoming overweight or obese and also bodyweight. Weight gain however, was found to be much higher when eating at fast-food outlets than at restaurants. Eating at fast-food establishments was associated with a greater increase in waist circumference over time than eating at restaurants. The mechanism that leads to weight gain and obesity is an imbalance between energy intake and energy expenditure and is driven by the consumption of foods with a high energy-density and of great portion sizes (8;9). A decrease in physical activity, and by 11 consequence a reduction in energy expenditure, is also conducive to obesity (38). Fast-foods are known to have a high energy density (39;40) and a high fat content and led to a high energy intake (Lachat C, Nago E, Verstraeten R, Roberfroid D, Van Camp J, Kolsteren P, unpublished data) (41). As shown previously, the latter were reported as having a high fat content (Lachat C, Nago E, Verstraeten R, Roberfroid D, Van Camp J, Kolsteren P, unpublished data) (41). The review by Rosenheck confirmed that more fast-food consumption is associated with increased caloric intake leading to weight gain (17). Our review adds to this that this association also holds for restaurant foods. Takeaway foods are foods purchased in a restaurant and often a fast-food establishment, to be consumed elsewhere. This review shows that eating takeaway foods frequently increased BMI in Australian women. This finding is in accordance with the fact that fast-foods and restaurant foods increase energy intake and led to weight gain and confirmed longitudinal data from French et al. (27) showing that fast-food use is associated with higher energy and fat intake and greater body weight in women in the USA. This review provided no evidence on canteen foods or school foods. Studies in adolescents showed that change in the frequency of fast-food visits from adolescence to young adulthood did not predict BMI z-score at young adulthood. Given that adolescents are a critical age group in which out-of-home eating was a predominant source of energy (41), it is important to study better the sources and quality of their out-of-home food sources and how different eating habits are associated with their nutrition status, particularly regarding the risk of overweight and obesity. Given that previous research have shown cross-sectionally how eating in canteens can be associated with optimal dietary patterns (42), additional research is needed to see how canteen foods can be used to prevent and control overweight and obesity in this age group. All the studies retrieved for this review were conducted in high-income countries, particularly the USA. We did not retrieve studies from low- and middle-income countries. This resulted in conclusions focusing on fast-foods and to a lesser extent on restaurant foods. It is important to note, however, that street foods are a key source of foods away from home in LMIC (41). Although they are important sources of traditional foods (43) and have shown to be valuable ways to promote healthy diets (44;45;45;45;45), various studies show that street foods undergo important changes towards high energy-dense fatty and sugary foods or soft drinks (5;46;47). The present review used a sensitive approach in searching potential articles to be included and used a syntax with a high sensitivity to identify relevant studies. At the same 12 time, it was not limited to out-of-home in general but also evaluated studies which assessed a specific source of out-of-home foods. Despite this approach, the number of longitudinal studies available and of those that could be included in this paper was small. Findings of this review are potentially biased by the fact that they relate only to out-of-home foods with high fat and energy contents (fast-foods and restaurant foods). Findings of this paper justify the need to monitor the nutritional quality of out-ofhome foods and its implication for public health. Further research should look at the differences in nutrient contents between home and out-of-home foods in general and between types of out-of-home foods in order to explain changes in consumers’ nutrition status. A standardization of the definition of out-of-home eating is needed to make the interpretation and comparison of results from future research easier. The classification of foods according to their place of preparation, which influences their chemical composition and nutritional quality, seems more appropriate compared with using the place of consumption. Research should also go beyond the monitoring of out-of-home eating and its implication for nutrition status. Various studies that have changed the composition or portion sizes of foods eaten out-of-home have shown promising effects on dietary intake and weight status (11;48-50). It is important however, to assess eating out comprehensively. Long-term intervention studies are needed to determine how to offer consumers healthy out-of-home foods and examine substitution effects between different sources of out-of-home foods or with home foods. This review calls for more research on the consumption of out-of-home foods and its longitudinal effect on nutrition status. It concludes that eating out-of-home foods frequently increases the risk of becoming overweight or obese, bodyweight, waist circumference and women’s BMI. Increase in weight and waist circumference is greater when eating at fast-food outlets than at restaurants. 13 Table 1. Inclusion and exclusion criteria Inclusion criteria Type of study Prospective study, including intervention study targeting dietary modification or weight management Topic Uses any definition of out-of-home eating, including only one kind of out-of-home foods Measures included - - Subjects - Reports longitudinally at least an indicator of weight status (weight, BMI, waist circumference, waist-and-hip ratio, skinfolds, body composition indices) as primary or secondary outcome Reports longitudinally or not at least the percent energy or the frequency of out-of-home eating as primary or secondary outcome Human subjects from all age groups, healthy and without specific dietary requirements Infants, children, adolescents and/ or adults, males and/ or females, of any race or ethnicity and from any country Exclusion criteria - - - Cross-sectional study review conference paper qualitative study editorials, book or article comments, policy briefs case study Not about out-of-home eating About the cost of or expenditures on out-of-home foods, About food safety About food choices or preferences Reports no indicator of weight status No report of the percent energy or the frequency of out-of-home eating Reports cross-sectionally an indicator of weight status Patients or institutionalized subjects Subjects with particular nutrient requirements such as sport people or soldiers, pregnant or lactating women Underweight, overweight or obese people only 14 Table 2. Description of the articles of the review Ref. Authors and Countries Participants Sample size publication Start of data Follow-up Source collection length data of Type of study Definition source of OH year (32) Ball or foods et al. Australia (2002) 18-23years Women, n=14779 1996 4 years WHA Interrupted nationally time Takeaway food series representative (26) Bédard et al. Canada (2010) 30-65year n=77 20011 12 weeks Primary data Women, urban Cohort study, Fast-food Intervention promoting the Mediterranean food pattern (25) Bes-Rastrollo Spain et al. (2009) University graduates n=14106 1999 Mean age of 37years 4.4years on SUN Interrupted average time series Viner and UK Cole (2006) 16 years, males and females, and fast-food n= 5723 1970 nationally Naska et al. Denmark, 35-74years (2011) France, Men and women 15 years: from 16 to representative (22) of consumption Males and females, (30) Place 1970 British Interrupted Birth Cohort series EPIC- Interrupted PANACEA series time Fast-food and takeaway 29-30 years n=36994 1995 1.1 years to 9.4 time Place of consumption: Germany, restaurant Greece, Italy, (restaurant The cafeteria, Netherlands, fast-food) and Norway, work bar, 15 Spain, (workplace) Sweden, UK (19) Duffey et al. USA (2009) 18-30years,Black n=5115 1985 13 years: and White, male and years 7, 10 female, urban and 20 CARDIA Interrupted time series Place of consumption: Fast-food and restaurant (29) Li et al. USA (2009) 50-75years n=1221 2006 1 year Men and women Portland Interrupted Neighborhood series time Fast-food time Place Environment and Health Study (18) Duffey et al. USA (2007) 18-30years,Black n=5115 1985 3 years: from and White, male and 7th female, urban year CARDIA 10th to Interrupted series of consumption: fast-food and restaurant (23) Niemeier et USA al. (2006) 11-21years, 7-12th n=14738 1996 5 years Add Health graders, males and females, Interrupted time series Place of consumption: nationally fast-food representative (24) Pereira et al. USA 18-30years n=5115 1985 (2005) 15 years: baseline CARDIA to Interrupted time series Levitsky et al. (2004) USA University freshmen n=68 2000 12 weeks of consumption: 15th year (20) Place fast-food Primary data Interrupted series time Place of consumption: all-you-can-eat hall, pay-cash 16 hall, restaurant (31) Thompson et USA 8-12years, girls n=196 1990 1 to 10 years Primary data Interrupted al. (2004) time series Quick-service food, coffee- shop food and restaurant food (21) Ma et al. USA (2003) (27) 20-70years n=641 1994 1 year SEASONS Interrupted Men and women French et al. USA (2000) series 20-45 years Low- and time n=998 NR 3 years high- income women Pound of Weight Study (POP) prevention of consumption Controlled trial prevention Place 2 Fast-food gain intervention (28) Jeffery and French (1998) USA 20-45years, men, low-income and n=1226† NR 1 year high-income women Pound of Controlled trial2 prevention Weight Study (POP)3 prevention Fast-food gain intervention 1 : This information was retrieved from “Goulet J; Lamarche B; Nadeau G and Lemieux S. Effect of a nutritional intervention promoting the Mediterranean food pattern on plasma lipids, lipoproteins and body weight in healthy French-Canadian women. Atherosclerosis 2003; 170: 115-124”. 2 : Studies reporting on a controlled trial but without comparing controls and treatments in regard to the association of out-of-home eating and weight status 3 : This information was retrieved from the study by French et al. (2000) also included in this review. Abbreviation: NR: not reported; WHA: Australian Longitudinal Study on Women’s Health; SUN: Seguimiento Universidad de Navarra (University of Navarro Follow-up); CARDIA: Coronary Artery Risk Development in young Adults; EPIC-PANACEA: European Prospective Investigation Into Cancer-Physical activity, Nutrition, Alcohol, Cessation of smoking, eating Out of Home and Obesity; SEASONS: Seasonal Variation of Blood Cholesterol Study; Add Health: National Longitudinal Study of Adolescent Health. 17 Table 3. Summary of studies assessing the risk of becoming overweight or obese over time when eating out-of-home Ref Country Baseline Exposure Follow-up characteristics (25) Spain Outcome Findings length 27% ate OH ≥ 2 times/ week Weekly frequency of away- 2 BMI (kg/m ): 23.1±3.6 (subjects from-home meals 4.4 years on average Incidence of Eating out ≥ 1 time/ week associated 1 with a 1.22-1.33 higher risk of becoming overweight/obesity not eating out), 23.3±3.7 (eating overweight/obese compared to not eating out 1 time/week), 23.6±3.8 (eating out(p<0.001) out ≥ 2 times/ week), p<0.001 (21) USA 29.7% meals OH Frequency 2 of breakfasts, Men: mean BMI 28.6 kg/m , 48% lunches and dinners eaten overweight, 27% obese OH 1 year to 1st quartile2, Average BMI over Compared others 1 year associated with 2.21-2.98 higher risk of obesity for breakfast frequency, 1.89- Women: mean BMI 26.6 kg/m2, 2.25 higher risk for dinner frequency, but 33% overweight, 20% obese 30-60% lower risk for lunch frequency 1 : participants with BMI < 25 kg/m at baseline and BMI ≥ 25 kg/m at follow-up, WHO references 2 : the frequency of eating each meal out-of-home was calculated by dividing the number of each meal out-of-home by the total number of days on which the meal was 2 2 consumed. Subjects were then separated into quartiles based on this frequency. Abbreviation: OH: out-of-home 18 Table 4. Summary of studies evaluating the longitudinal association of bodyweight with out-of-home eating Ref Country Baseline Exposure Follow-up characteristics (25) Spain Outcome Finding length 27% ate OH ≥ 2 times/ week Weekly frequency of 4.4 ±1.7 years Annual Weight (kg): 65.5±12.7 (subjects away-from-home on average change not eating out), 67.2±13.5 (eating meals weight Eating out 1 time/week and ≥2 times/week associated respectively with 15g and 129g weight gain per year (p<0.001) compared out 1 time/week), 69.4±14.0 (eating to not eating out. Also associated out ≥ 2 times/ week), p<0.001 respectively with 1.12 and 1.36 higher risk of gaining ≥2 kg per year (p=0.001) (22) (19) 1 Denmark, Italy, % EI from restaurant : EI France, Sweden, Men: 3.6-12.4; Women: 3.0-7.2 eaters, Germany, UK, % EI from work2: restaurant, Greece, The Men: 4.3-15.1; Women: 1.1-11.4 (kg/m2)3: Netherlands, BMI Norway, Spain Men: 23.4-28.4; Women:22.9-29.0 USA weight In men, weak positive but not significant at change (weight at association of annual weight change and: of follow-up minus 1) eating at restaurant with EI close to the participants eating at weight on dietary average of restaurant eaters (β=+0.05, restaurant recall day, divided p=0.368); 2) increase of 500 kcal in EI at by follow-up time) restaurant (β=+0.01, p=0.836) Weight change over 1 time/week more fast-food consumption 13 years associated with 0.15 ±0.05 kg weight gain over Change 4 frequency 30.3% overweight, 23.2% obese4 restaurant EI % and 1.1 to 9.4 years at work 4 1.9±2.5 times/week at fast-foods 2.3±3.2 times/week at restaurant of in weekly of 13 years fast- Annual 13 years and for restaurant food, this was food and restaurant 0.09±0.04 kg food consumption (29) (24) USA USA Mean BMI: 29.1±6.5 kg/m2 Weekly frequency of 21% ate at fast-foods ≥ 1 time/ wk fast-food visits 5 Mean fast-food use : Weekly fast-food Black Men:2.4 times/week frequency and change Black Women:1.8 times/week in weekly fast-food 1 year 15 years Weight change over 1-2 visits per week to fast-foods associated 1 year with 0.65 kg weight gain Weight change over Increase of 3 times/ week in 15-y fast-food 15 years weekly frequency increased weight by 1.8 kg (p<0.0001) in White people 19 White Men: 2.4 times/week frequency White Women:1.6 times/week Mean bodyweight6: Black: 72.4-73.5 kg White : 69.8-71.5 kg (20) USA Mean BMI: 20.8±2.1 kg/m2 Weekly frequency of Most subjects had BMI in normal breakfast, lunch and 2 range (19.8-22.7kg/m ) 12 weeks Weight change over Eating breakfast and lunch at all-you-can- 12 weeks eat hall explains 10% of the variance of dinner at all-you-can- weight gain. Initial weight adjusted for, eat hall, cash-op hall eating lunch at a restaurant explained 5% and restaurant of the variance of weight gain and dinner at a cash-op, 4% and variance explained improved from 58 to 71% (27) USA Mean weight : 72.8 kg Weekly frequency of 2 Mean BMI: 27.0±6.0 kg/m 3 years fast-food meals Weight change over Increase of 1 meal/week at fast-food 3 years increases weight by 1.68 kg over 3 years 36.8% ate fast-food ≥ 2 times/week 1 : Mean contribution to daily energy intake of eating at restaurant, from a country to another 2 : Mean contribution to daily energy intake of eating at work, from a country to another 3: Mean BMI, from a country to another 4 : Here, baseline values correspond to values measured at the 7 th year 5 : Significant difference between men and women, between Black and White 6 : bodyweight for Black and White people, varying across subgroups of subjects formed on the basis of weekly fast-food frequency Abbreviation: OH: out-of-home 20 Table 5. Summary of studies assessing the longitudinal association of BMI and BMI z-score with out-of-home eating Ref Country Baseline Exposure characteristics Follow-up Outcome Findings BMI Compared to women never or rarely eating length BMI (32) Australia 68% ate takeaways≥1time/week Frequency of eating takeaway 13.9% overweight and 5.9% obese foods 4 years category (maintainers versus gainers) takeaway foods, those eating once a week 1 were 15% less likely to be weight maintainers (26) Canada (25) Spain Mean BMI2: 25.4 to 25.8 kg/m2 Change in weight of fast-foods Mean fast food intake: 51.7 g/ day consumed over 12 weeks Cf. table 3 Weekly frequency of away-fromhome meals 12 weeks BMI change Change in fast-food consumption over over 12 weeks 12weeks not correlated with BMI change 4.4 years on Annual change Eating ≥2 times/week associated with average in BMI +0.07 kg/m2 BMI change per year (p<0.001) compared to not eating out (18) USA 1.9±2.4 times/week at fast-foods3 Weekly frequency of fast-food 2.6±3.1 times/week at restaurant3 3 30.6% overweight, 23.3% obese 3 years Change in BMI Increased change in fast-food consumption and restaurant food consumption from year 7 to increases 3-year change in BMI but not for at years 7 and 10, change in the year 10 restaurant food. Increase of fast-food use frequencies from year 7 to year 10 of 1time/week increases mean BMI by 0.20 kg/m2.Increase of both fast-food and restaurant associated with 0.29 kg/m2 increase in BMI (28) USA Fast food (meals/week): Number of fast-food meals per Men: 2.2±2.0 week 1 year 1-year change in No correlation between fast-food eating BMI and BMI over 1 year HIW: 1.5±1.7; LIW: 1.7±1.7 BMI (kg/m2): men: 27.8±4.6 21 HIW: 25.9±4.9; LIW: 27.7±6.9 BMI z-score (30) UK 22% ate fast-food ≥ 2 times/week Baseline weekly frequently of 8.2% obese4 eating at fast-food or take-away 15 years BMI z-score at Eating fast-food or takeaway meals twice follow-up or more a week at baseline increased BMI outlets (23) USA Mean age: 15.9y (SEM: 0.11) 2 Change in the number of days on BMI: 22.9 kg/m (SEM: 0.12) which fast-foods were consumed 28.7% overweight;10.9% obese in the last 7 days z-score by 0.14 to 0.21 unit 5 years BMI z-score at Change in fast-food consumption from follow-up baseline (adolescence) to follow-up (young adulthood) did not predict BMI z-score at follow-up (31) USA Median age: 9 years 4% overweight and 0% obese 71% ate OH Baseline weekly frequency and 5 1 to 10 years Change in BMI Eating at quick-service twice or more a percent of weekly energy intake z-score from week at baseline associated with greater of quick-service, coffee-shop and baseline to mean increase in BMI z-score (+0.82 unit) restaurant foods follow-up than eating once a week (+0.20 unit) or not at all (+0.28 unit) 1 :Maintainers were defined as women whose BMI at follow-up was within 5% of their baseline BMI. Gainers were women whose BMI at follow-up was more than 5% greater than their baseline BMI 2 : Mean BMI, varying among four subgroups of subjects formed on the basis of medians of fast-food consumption and medians of changes in Mediterranean dietary (arbitrary) score 3 : For this paper, baseline values are those measured at the 7th year 4: 5 defined as ≥ 95thBMI-for-age percentile of the UK 1990 growth reference : defined respectively as 85 to 94.9th and ≥ 95thBMI-for- age percentile of the growth reference of the US Center for Disease Control and Prevention (CDC) Abbreviation: OH: out-of-home; HIW: high-income women; LIW: low-income women; SEM: Standard error of the mean 22 Table 6. Summary of studies evaluating the longitudinal change in waist circumference when eating out Ref Country Baseline Exposure Follow-up characteristics (26) (19) Canada USA Outcome Findings Change in WC over Change in fast-food consumption over 12 12 weeks weeks not correlated with change in WC Change in WC over 1 time/week more fast-food consumption 13 years associated with a 0.12 ±0.04 cm increase length Mean WC: 81.5 to 84.8 cm Change in weight of fast-foods Mean fast food intake: 51.7 g/ day consumed over 12 weeks 1.9±2.5 times/week at fast-foods1; Change in weekly frequency of 2.3±3.2 times/week at restaurant 1 1 30.3% overweight, 23.2% obese ; fast-food and restaurant 12 weeks 13 years food consumption over 13 years in WC over 13 years and for restaurant WC:84.0±14.1 cm1 (29) 1 USA food, this was 0.08±0.03 cm 2 Mean BMI: 29.1±6.5 kg/m ; 21% Weekly frequency of fast-food ate at fast-foods ≥1 time/week visits 1 year Change in WC over 1.06 cm increase in WC with 1-2 1year visits/wk to fast-foods during 1 year : Here, baseline values correspond to values measured at the 7 th year. Abbreviation: OH: out-of-home; WC: waist circumference 23 Table 7. Summary of the methodology of the studies Ref Sampling Representativeness Measurements Participation Anthropometrics Validity rate (32) and reliability tested 65% Self-report Only young women (n=9657) weight and height on food habits, at at baseline of No and Used Questionnaire No 94% Measurement sample (n=72) weight, height and university graduates Males and females Multivariate Adjustment for logistic regression occupation, student status, marital status, parity and new parity Self-reported Convenience Only Under/over-reporting and adjustment baseline of NR Quantitative Yes Mixed procedures 1 FFQ, IA, at for excluded WC at baseline, 6 baseline, 6 and measurements and No and 12 wk. Used 12 weeks Tukey-Kramer confounders BMI and WC (25) Statistical method only BMI Only urban women Validity/reliability of OH measure National sample follow-up. (26) Food intake Analysis repeated over-reporter adjustment for test 95% Self-report Least-squares Under (n=13373) weight at baseline quantitative multivariate reporters excluded and every 2-year. FFQ, SA, at regression, NR baseline only conditional subjects included measurement. Used logistic regression Adjustment for age, weight and sex, smoking, fiber, on and changes incidence overweight of height BMI and of and obesity with WHO Yes (for weight) Semi- Yes non Cox Tested proportional alcohol hazards analysis intakes, and over- similar and to energy education, following special diet, PA and baseline BMI 24 references (30) National sample 78% Measurement of Standard Males and females (n=4461) height and weight methods at 16years and self- baseline). report at 30. Used No BMI z-score with report) (for Questionnaire (at self- NR Regression of Adjustment for BMI on food habits, BMI z-score at z-score at 30years on fast- height at 16 and 30, food/ sex and social class baseline only, SA takeaway at 16years, eating at 16years UK 1990 growth references (22) Samples from 10 66% Mainly European countries (n=24310) of self-report height No and Single-day 24h Yes dietary Multivariate Under mixed-effects reporters excluded over- linear regression Adjustment for age, General population weight on day of recall, mainly but only women in 24-h IA France, weight at follow- status, Naples (Italy) and up. BMI on dietary recall Utrecht change Norway, (The recall, Used then education, weight smoking occupation, day, follow-up time, Netherlands) (19) and total EI and PA Males and females 81% (year 7) Measurement of Standard Questionnaire Black and White 74% (year height, weight and methods on From 4 US urban 10)*; 72% WC at years 7, 10 habits, at years areas (year 20) and 7, 10 and 20, status, IA television 20. Used weight and WC No dietary Fixed-effect Adjustment for age, longitudinal education, regression structure, family smoking hours of viewing, total EI and PA (29) Convenience 94% Measurement of Standard Questionnaire sample (n=1145) height, weight and methods on dietary Males and females, WC, at baseline and intake, urban, follow-up. baseline Used at and No Multilevel linear Adjustment for regression neighborhood-level variables and residentlevel variables like 25 Incentives weight and WC follow-up, IA age, sex, education, smoking, BMI (18) Males and females 81% (year 7) Measurement of Standard Questionnaire Black and White 79% height and weight, methods on From 4 US urban 10)* (year areas No dietary Multivariate Adjustment for race, linear regression sex, age, study center at years 7 and10. habits, at years and year 7 education, Used BMI and BMI 7 and 10, IA income, change family structure, smoking status, fast-food and restaurant frequency, PA and EI (23) National sample th 7-12 graders 67% Mainly (n=9919) measurement Males and females of Standard Questionnaire methods on dietary height and weight, habits, at baseline baseline follow-up. and Used No Multivariate For baseline BMI z- linear regression score, at race/ethnicity, sex, age, month of and follow-up, IA interview, maternal obesity, parental BMI z-score with education, CDC behavior, change in growth references sedentary sedentary behavior, PA (24) Males and females 74% at year Measurement of Standard Questionnaire Black and White 15* height, weight and methods on dietary No Multivariate Adjustment for sex, linear regression age, study centre, From 4 US urban WC at years 0, 2, habits, at years education, areas 5,7, 10 and 15. 0, 2, 5,7, 10 weight Used weight change and 15, IA alcohol consumption, and smoking television baseline height, status, viewing, 26 dietary factors and PA (20) Convenience 88% Measurement of Standard Questionnaire sample (n=60) weight at baseline methods on food habits analysis at stepwise multiple Freshmen from one and follow-up. University Used weight change NR follow-up only Correlation regression Males and females Adjustment for initial and weight with maximal R improvement (31) Convenience 52% Measurement of Standard 7-day dietary sample (n=101) weight and height, methods records, at baseline and Girls only at baseline Incentives follow-up. and Analysis of variance adjusted for unbalanced follow-up, cell size BMI z-score with self-reported Duncan’s multiple CDC but probed by range test. Used growth references (21) No Adjustment for baseline BMI z-score and telephone Convenience 78% Measurement of Standard 24-hour sample (n=503) weight, at baseline methods dietary recall Males and females and 5 time points Incentives Measurement No Multivariate Subjects logistic regression tested excluded similar to on 2 weekdays subjects included and 1 weekend Adjustment for age, height at baseline day, gender, education, EI BMI averaged over baseline and 5 all of measurement time days. Used average BMI with at and PA † points , IA. WHO references (27) Convenience 89% Measurement of Standard Questionnaire sample (n=891) weight at baseline methods on food habits, No Multivariate Adjustment linear regression baseline for fast-food 27 Women (including and low-income) visit each Measurement annual of IA, at baseline frequency and weight and and each annual visit marital status, ethnicity, income, age height at baseline. and treatment group Used weight change (28) Convenience 86% Measurement of Standard FFQ, IA, at sample (n=1059) height and weight methods baseline Men and women at (including follow-up. income) low- baseline and Used follow-up and No Multivariate Adjustment for age, linear regression education, baseline smoking and BMI and treatment group BMI th *: 74% at the 10 year represents the participation rate based on the whole cohort whereas 79% at the 10 th year is the participation rate based on the surviving cohort (excluding dead people); 74% at the 15th year is also based on the surviving cohort. † : the frequency of eating each meal out-of-home was calculated by dividing the number of each meal out-of-home by the total number of days on which the meal was consumed. Abbreviation: WC: waist circumference; FFQ: food frequency questionnaire; IA: interviewer-administered; SA: self-administered; PA: physical activity; EI: energy intake 28 Articles identified from databases (n=7319):Medline (n=2859), CAB (n=200), Cochrane (n=388), Web of Knowledge (n=2103), EMBASE (n=640), AGRICOLA (n=833), INGENTA (n=220), Bioline International (n=76) Doubles removed(n=1154) Articles individually screened (n=6165) Articles not eligible for review based on title (n=2823) Articles retained for abstract screening (n=3342) Articles excluded after reading of abstracts (n=3214): not on humans (n=2); reviews (n=13); no dietary assessment (n=1642); not about out-of-home eating (n=1304), not original studies (n=215); cannot find paper (n=34); cross-sectional (n=4) Articles retained for reading of full text (n=128) Articles excluded after full reading (n=115) Articles retained after full reading (n=13) Papers identified from screening of references (n= 2) Articles included in the review (n=15) Figure 1. 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