Obesity
Original Article EPIDEMIOLOGY/GENETICS
What Distinguishes Weight Loss Maintainers of the German Weight Control Registry from the General Population? Silke Feller1, Astrid M€ uller2, Andreas Mayr3, Stefan Engeli4, Anja Hilbert5, and Martina de Zwaan2
Objective: Differences between successful long-term weight loss maintainers and the general population with regard to eating and weighing habits, non-normative eating behaviors, and eating-related and general psychopathological parameters are unknown. Methods: Self-identified weight loss maintainers from the German Weight Control Registry (GWCR, n 5 494) were compared with a representative sample of the general German population (n 5 2,129). The samples did not differ in current BMI. Using the same assessment instruments in both cohorts, a variety of eating-related and psychological variables were determined. Results: The GWCR participants reported more self-weighing and higher eating frequency but less hot meal consumption and more eating-out-of-home. Binge eating, compensatory behaviors, and concerns about shape and weight were reported more often by successful weight loss maintainers. Scores of depression and worrying about health were slightly higher whereas severity of somatic symptoms was less pronounced in the GWCR participants. Conclusions: Overall, our data suggest that successful weight loss maintainers are characterized by more concerns about shape and weight, greater binge eating frequency, and higher use of compensatory behaviors. The latter suggests that weight loss maintenance might not only be achieved by healthy strategies but also by non-normative behaviors which might increase the vulnerability for weight regain. Obesity (2015) 00, 00–00. doi:10.1002/oby.21054
Introduction The challenge of long-term weight loss maintenance is well known. Addressing this issue, the National Weight Control Registry (NWCR) in the US represents the largest prospective investigation on successful long-term weight loss maintenance. In summary, the NWCR found high levels of physical activity, eating a low-calorie, low-fat diet, eating breakfast regularly, self-monitoring weight, and maintaining a consistent eating pattern across weekdays and weekends as positive predictors for weight loss maintenance. Low levels of depression and disinhibited eating, low levels of binge eating, and medical triggers for weight loss were also associated with longterm success. Individuals who had kept their weight off for at least 2 years also had markedly increased odds of weight loss maintenance over the following year (1-11).
In the NWCR, successful weight loss maintainers (WLM) were compared longitudinally with weight regainers. The only study comparing WLM with treatment-seeking obese (12) found that WLM were more physically active and showed more dietary restraint and less dietary disinhibition compared to treatment-seeking obese individuals. Environmental factors such as availability of physical activity equipment, TVs, and high-fat foods at home also distinguished WLM from treatment-seeking obese individuals. Differences between successful WLM and the general population with regard to eating and weighing habits, non-normative eating behaviors, and eating-related and general psychopathological parameters are largely unknown. Even though successful WLM might exhibit les psychopathology, less non-normative eating behaviors, and more healthy eating behaviors compared to weight regainers
1
German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Epidemiology, Nuthetal, Germany 2 Department of Psychosomatic Medicine and Psychotherapy, Hannover Medical School, Hannover, Germany. Correspondence: Martina de Zwaan ([email protected]) 3 Department of Medical Informatics, Biometry and Epidemiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany 4 Institute of Clinical Pharmacology, Hannover Medical School, Hannover, Germany 5 Integrated Research and Treatment Center Adiposity Diseases, Department of Medical Psychology and Medical Sociology, University of Leipzig Medical Center, Leipzig, Germany.
Funding agencies: The study was supported by the BMBF (German Federal Ministry of Education and Research) grant 01GI0835 within the German Competence Network of Obesity and by the BMBF grant 01EO1001. The BMBF had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. Disclosure: The authors declare no conflict of interest. €ller, and Anja Hilbert are responsible for the study design. Andreas Mayer and Silke Feller analyzed the data. All Authors contributions: Martina de Zwaan, Astrid Mu authors were significantly involved in data interpretation, and Silke Feller wrote the first draft of the manuscript. All authors were involved in writing the paper and gave final approval of the submitted and revised version. Received: 17 November 2014; Accepted: 21 January 2015; Published online 00 Month 2014. doi:10.1002/oby.21054
www.obesityjournal.org
Obesity | VOLUME 00 | NUMBER 00 | MONTH 2015
1
Obesity
and obese weight loss participants (1,5), they might still show more psychopathology and non-normative eating behaviors compared to the general population. We may also assume that WLM and regainers share problematic behavioral and psychological characteristics which would not be ascertainable by comparing only those two groups. Contrasting successful WLM with the general population may elucidate information on problematic behavioral and psychological characteristics that also may be present successful WLM. Weight loss and weight maintenance treatment approaches might benefit from this information. We aimed at extending the knowledge gathered with the NWCR by comparing self-identified WLM from the German Weight Control Registry (GWCR) with a representative sample of the general German population using the same assessment instruments in both samples.
Methods The German Weight Control Registry The GWCR was established to investigate psychosocial mechanisms behind successful weight loss maintenance to provide a basis for improved weight loss and maintenance therapy strategies. The registry includes a volunteer sample of the general adult population that fulfilled the inclusion criteria by (1) having intentionally lost at least 10% of their maximum body weight (not considering pregnancy) and (2) having kept it off at least 1 year, which is in accordance with the definition of weight loss maintenance (13). Interested individuals were invited to contact the organizers of the study via letter, phone, or Web and were included if they met the inclusion criteria and signed a written informed consent. The participants were then asked to fill out a battery of identical Web or paper-and-pencil questionnaires. In doing so, 494 men and women were enrolled in the registry between October 2009 and April 2011 (14). The study was approved by the Ethics Committee of the Medical School at the University of Erlangen-Nuremberg. All participants gave written informed consent.
Population-based survey To assess the variables used in the GWCR in a representative population sample, a population survey of adults was conducted between May and June 2011 by USUMA, a commercial institute specialized in market, opinion, and social research. For this purpose, participants aged between 18 and 65 years were selected from the general German population from different regions by random digit dialing followed by computer-assisted telephone interviews. Similar to the GWCR, participants were then asked to complete questionnaires by choosing between the Web or paper-and-pencil version (14). A total of 2,286 men and women were recruited for the purpose of this study. About 157 individuals had to be excluded because of missing values and missing weight-related measures, respectively, leaving 2,129 participants for the analyses. All participants were visited in-person and informed about the study procedures by a trained research assistant. They also received a written explanation of the study including information on data management and provided oral informed consent prior to assessment. Oral consent is common in survey research in Germany. The ethical guidelines of the International Code of Marketing and Social Research Practise by the
2
Obesity | VOLUME 00 | NUMBER 00 | MONTH 2015
Weight Loss Maintenance Feller et al.
International Chamber of Commerce and the European Society for Opinion and Marketing Research were followed.
Measures Besides age and sex, the following socio demographic characteristics were assessed: living in a partnership (yes vs. no), being employed (yes vs. no), having an academic degree (yes vs. no). Based on previous literature (1–11) questions assessing various aspects of eating and weighing habits were applied. These included eating frequency and regularity (mean eating occasions per day; consumption of hot meals, breakfast, and fast-food), location of eating (sum of days with different occasions of eating out-of-home), as well as current weighing frequency (from 1 5 “several times daily” to 7 5 “never”). Eating consistency was determined by the ratio of mean eating occasions on weekdays and weekends. Ratios being closer to 1 reflect a higher consistency during the whole week (2). Body height as well as current and maximum weights were assessed by self-report for calculation of body mass index (BMI, kg/m2). Participants were asked how often they had intentionally lost weight (more than 5 kg). The self-reported number of intentional weight loss attempts was used as a measure of weight cycling. Even though no information was available on weight regain following each weight loss, the assumption of at least partial weight regain is supported by other studies (15). To assess non-normative eating behaviors and eating-related psychopathology we used diagnostic items for binge eating disorder (BED) and bulimia nervosa (BN) of the German version of the Eating Disorder Examination-Questionnaire (EDE-Q) (16,17). These items included (1) the importance of shape and weight for self-evaluation (“Over the past four weeks, has your shape/weight influenced how you feel about (judge, think, evaluate) yourself as a person?”), which is rated on a 7-point forced-choice format (0 5 no importance, 6 5 supreme importance), (2) binge eating episodes defined according to DSM-5 criteria (18) (eating an objectively large amount of food with a sense of loss of control), and (3) compensatory behaviors including self-induced vomiting, laxative and diuretic misuse, driven exercising, and 24-hour fasting. Binge eating and any compensatory behaviors were dichotomized for any occurrence ( 1 episode vs. 0 episodes) over the past 28 days. In addition, binge eating frequencies of 4 episodes over the past 28 days and 4 episodes per month over the past 3 months were calculated which corresponds with the DSM-5 frequency requirement for BED and BN (18). With respect to the importance of shape and weight, a composite mean shape/weight over evaluation score was created consistent with prior studies because of high correlations between the two items (19). A clinical cutoff score of 4 was used indicating an at least moderate importance of shape and weight evaluation (16,19). Depressive and somatic symptoms were assessed with subscales of the German version of the Patient Health Questionnaire (PHQ-D) (20–22). The Patient Health Questionnaire depression severity scale (PHQ-9) is a standard tool for assessing depressive symptoms according to DSM-IV-TR. Participants were asked to rate their answers on a 4-point scale from 0 (“not at all”) to 3 (“nearly every day”). The Patient Health Questionnaire somatic symptom severity scale (PHQ15) assesses the most common physical complaints such as stomachaches or headaches. Each symptom is scored from 0 (“not bothered at
www.obesityjournal.org
Original Article
Obesity
EPIDEMIOLOGY/GENETICS
all”) to 2 (“bothered a lot”). For both scales, total sum scores were calculated, for which higher values indicate more severe symptoms. For the PHQ-9 an algorithm is available allowing to calculate the presence of a major depressive episode (MDE). The internal consistency (Cronbach’s a) of both scales was acceptable (PHQ-9: a 5 0.84, PHQ-15: a 5 0.76). Finally, the PHQ-D asks about level of distress (“In the last 4 weeks, how much have you been bothered by worrying about your health?”). Answer possibilities were scored from 0 (“not bothered at all”) to 2 (“bothered a lot”).
Statistical analysis Characteristics of participants of the GWCR and those of the population-based survey are presented by means (6 SD) for continuous variables and by n (%) for categorical variables. Differences between groups were assessed by v2 tests and Wilcoxon tests. To compare both samples, logistic regression models with “sample” as the dependent variable were conducted. Odds ratios (ORs) and confidence intervals (95% CIs) were determined based on the calculated effect estimates. To account for possible confounding effects based on socio demographic differences, multiple adjusted models were used. The first model included age and sex as covariates only. The second model was additionally adjusted for employment status, education, and partnership. For this model P-values were calculated and corrected by false discovery rate to avoid problems regarding multiple testing. In a third model, mutual adjustment was conducted by entering all variables simultaneously to investigate the independence of the observed associations. All analyses were performed with SAS statistical software (SAS Enterprise Guide version 6.1; SAS Institute, Cary, North Carolina, USA). Statistical significance level was set at P < 0.05.
Results The entire study population is described in Table 1. GWCR participants were more often women, slightly older, better educated, more often employed, and more often living in a partnership compared to participants in the general population sample. Although current BMI did not differ between groups, GWCR participants reported a higher maximum BMI and a higher frequency of weight cycling compared to participants in the general population sample. GWCR participants reported a higher eating frequency per day but ate fewer hot meals. These individuals also ate out of home more often compared to participants in the general population sample. No differences were observed for breakfast skipping, eating consistency between weekdays and weekends, and fast-food consumption between samples. In addition, GWCR participants reported a higher frequency of weighing themselves compared to the general population sample. Once daily weighing occurred in 44% of the GWCR participants but only in 16% of the general population, the numbers for weighing once weekly were 11% vs. 17%. As shown in Table 1, GWCR participants reported more binge eating and more compensatory behaviors than the population sample. Furthermore, GWCR participants revealed greater importance of shape or weight. The clinical cutoff score of 4 occurred in 54.9% of GWCR participants and in 20.0% of general population participants. Finally, GWCR participants were significantly more worried about their health, but revealed lower scores on somatic symptoms. No difference was found for depressive symptoms. A major
www.obesityjournal.org
depressive episode (MDE) was found in 5% of GWCR participants and 3% of the population based sample. The results of the three adjusted logistic regression models are presented in Table 2. In the age- and sex-adjusted model (model 1), GWCR participants had a higher eating frequency per day, a higher frequency of eating out, a higher weighing frequency, a higher occurrence of binge eating and compensatory behaviors, and a higher importance of shape and weight for self-evaluation compared to the population sample. Eating hot meals and the occurrence of somatic symptoms were more frequent in the general population sample compared to the GWCR sample. After controlling for all socio demographic variables (model 2) the odds ratios remained quite similar except for worrying about health and depression which were now also found to be significantly higher in GWCR participants compared to the population sample. Correction for multiple testing did not diminish the associations. Similarly, after mutual adjustment (model 3), the reported associations slightly altered in strength but persisted completely. Eating frequency consistency between weekdays and weekends as well as eating breakfast or fast-food showed no differences between the two samples in either model.
Discussion Overall, the successful WLM of the GWCR differed from the general population in important aspects of eating and weighing habits and non-normative eating behaviors as well as eating-related and general psychopathology. These findings were robust against controlling for socio demographic variables, controlling for multiple testing, and mutual adjustment for all variables.
Self-weighing and eating frequency Successful WLM from the GWCR reported weighing themselves more frequently and indicated a larger daily eating frequency in comparison to the representative general population sample. However, no differences were found regarding eating consistency across weekdays and weekends. Regular self-weighing is a useful method to promote weight loss and maintenance, as shown in cohort studies and randomizedcontrolled trials (1,23–25). The potential efficacy of consistent selfmonitoring of weight has been based on self-regulation theory. Eating frequency has been negatively related to BMI in some (26) but not all studies (27), whereas dieting consistency has been shown to be positively associated with weight loss maintenance (2,28). Eating more frequently and maintaining a consistent diet regimen across the week may help to control hunger and decrease the chance of overeating. However, a review of controlled feeding studies suggests that increased eating frequency has minimal, if any, impact on appetite control and food intake. Rather, reduced eating frequency seems to negatively affect appetite control (29). Overall, participants from both cohorts exhibited a high eating frequency and diet consistency and the differences, even though significant, were small.
Eating out and other eating habits The frequency of hot meal consumption was lower and eating-outof-home occurred more often in GWCR participants compared to
Obesity | VOLUME 00 | NUMBER 00 | MONTH 2015
3
Obesity
Weight Loss Maintenance Feller et al.
TABLE 1 Characteristics of German Weight Control Registry participants and a representative German population sample
German Weight Control Registry
N Socio demographic characteristics Sex (women vs. men) Age (years) Employment (yes vs. no) Academic degree (yes vs. no) Partnership (yes vs. no) Anthropometric characteristics Current BMI (kg/m2) Maximum BMI (kg/m2) Weight cycling (sum of intentional weight loss attempts) Eating and weighing habits Weighing frequency (from 1 5 never to 7 5 several times daily) Eating frequency (meals and snacks per day) Eating frequency consistency (weekday-weekend ratio) Breakfast (days per week) Hot meals (days per week) Eating-out-of-home (sum of days per week) Fast-food (days per week) Eating-related psychopathology Shape and weight over evaluation (from 0 5 no importance to 6 5 supreme importance) Compensatory behaviors during the last 28 days (yes vs. no) Binge eating during the last 28 days (yes vs. no) Binge eating occurring 4 times during the last 28 days (yes vs. no) Binge eating occurring 4 times per month during the last 3 months (yes vs. no) General psychopathology Bothered by worrying about health (1 5 not bothered at all, 2 5 bothered a little, 3 5 bothered a lot) PHQ depression severity scale (PHQ-9, total score 0–27) PHQ somatic symptom severity scale (PHQ-15, total score 0–30)
Mean or %
494 494 489 492 490
60.7 47.62 76.9 46.8 81.6
494 494 494
25.69 33.20 5.07
491 486 486 486 487 403 428
SD
Population-based survey
N
Mean or %
SD
P-value 0.01a 0.008b 0.003a
Original Article EPIDEMIOLOGY/GENETICS
What Distinguishes Weight Loss Maintainers of the German Weight Control Registry from the General Population? Silke Feller1, Astrid M€ uller2, Andreas Mayr3, Stefan Engeli4, Anja Hilbert5, and Martina de Zwaan2
Objective: Differences between successful long-term weight loss maintainers and the general population with regard to eating and weighing habits, non-normative eating behaviors, and eating-related and general psychopathological parameters are unknown. Methods: Self-identified weight loss maintainers from the German Weight Control Registry (GWCR, n 5 494) were compared with a representative sample of the general German population (n 5 2,129). The samples did not differ in current BMI. Using the same assessment instruments in both cohorts, a variety of eating-related and psychological variables were determined. Results: The GWCR participants reported more self-weighing and higher eating frequency but less hot meal consumption and more eating-out-of-home. Binge eating, compensatory behaviors, and concerns about shape and weight were reported more often by successful weight loss maintainers. Scores of depression and worrying about health were slightly higher whereas severity of somatic symptoms was less pronounced in the GWCR participants. Conclusions: Overall, our data suggest that successful weight loss maintainers are characterized by more concerns about shape and weight, greater binge eating frequency, and higher use of compensatory behaviors. The latter suggests that weight loss maintenance might not only be achieved by healthy strategies but also by non-normative behaviors which might increase the vulnerability for weight regain. Obesity (2015) 00, 00–00. doi:10.1002/oby.21054
Introduction The challenge of long-term weight loss maintenance is well known. Addressing this issue, the National Weight Control Registry (NWCR) in the US represents the largest prospective investigation on successful long-term weight loss maintenance. In summary, the NWCR found high levels of physical activity, eating a low-calorie, low-fat diet, eating breakfast regularly, self-monitoring weight, and maintaining a consistent eating pattern across weekdays and weekends as positive predictors for weight loss maintenance. Low levels of depression and disinhibited eating, low levels of binge eating, and medical triggers for weight loss were also associated with longterm success. Individuals who had kept their weight off for at least 2 years also had markedly increased odds of weight loss maintenance over the following year (1-11).
In the NWCR, successful weight loss maintainers (WLM) were compared longitudinally with weight regainers. The only study comparing WLM with treatment-seeking obese (12) found that WLM were more physically active and showed more dietary restraint and less dietary disinhibition compared to treatment-seeking obese individuals. Environmental factors such as availability of physical activity equipment, TVs, and high-fat foods at home also distinguished WLM from treatment-seeking obese individuals. Differences between successful WLM and the general population with regard to eating and weighing habits, non-normative eating behaviors, and eating-related and general psychopathological parameters are largely unknown. Even though successful WLM might exhibit les psychopathology, less non-normative eating behaviors, and more healthy eating behaviors compared to weight regainers
1
German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Epidemiology, Nuthetal, Germany 2 Department of Psychosomatic Medicine and Psychotherapy, Hannover Medical School, Hannover, Germany. Correspondence: Martina de Zwaan ([email protected]) 3 Department of Medical Informatics, Biometry and Epidemiology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany 4 Institute of Clinical Pharmacology, Hannover Medical School, Hannover, Germany 5 Integrated Research and Treatment Center Adiposity Diseases, Department of Medical Psychology and Medical Sociology, University of Leipzig Medical Center, Leipzig, Germany.
Funding agencies: The study was supported by the BMBF (German Federal Ministry of Education and Research) grant 01GI0835 within the German Competence Network of Obesity and by the BMBF grant 01EO1001. The BMBF had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. Disclosure: The authors declare no conflict of interest. €ller, and Anja Hilbert are responsible for the study design. Andreas Mayer and Silke Feller analyzed the data. All Authors contributions: Martina de Zwaan, Astrid Mu authors were significantly involved in data interpretation, and Silke Feller wrote the first draft of the manuscript. All authors were involved in writing the paper and gave final approval of the submitted and revised version. Received: 17 November 2014; Accepted: 21 January 2015; Published online 00 Month 2014. doi:10.1002/oby.21054
www.obesityjournal.org
Obesity | VOLUME 00 | NUMBER 00 | MONTH 2015
1
Obesity
and obese weight loss participants (1,5), they might still show more psychopathology and non-normative eating behaviors compared to the general population. We may also assume that WLM and regainers share problematic behavioral and psychological characteristics which would not be ascertainable by comparing only those two groups. Contrasting successful WLM with the general population may elucidate information on problematic behavioral and psychological characteristics that also may be present successful WLM. Weight loss and weight maintenance treatment approaches might benefit from this information. We aimed at extending the knowledge gathered with the NWCR by comparing self-identified WLM from the German Weight Control Registry (GWCR) with a representative sample of the general German population using the same assessment instruments in both samples.
Methods The German Weight Control Registry The GWCR was established to investigate psychosocial mechanisms behind successful weight loss maintenance to provide a basis for improved weight loss and maintenance therapy strategies. The registry includes a volunteer sample of the general adult population that fulfilled the inclusion criteria by (1) having intentionally lost at least 10% of their maximum body weight (not considering pregnancy) and (2) having kept it off at least 1 year, which is in accordance with the definition of weight loss maintenance (13). Interested individuals were invited to contact the organizers of the study via letter, phone, or Web and were included if they met the inclusion criteria and signed a written informed consent. The participants were then asked to fill out a battery of identical Web or paper-and-pencil questionnaires. In doing so, 494 men and women were enrolled in the registry between October 2009 and April 2011 (14). The study was approved by the Ethics Committee of the Medical School at the University of Erlangen-Nuremberg. All participants gave written informed consent.
Population-based survey To assess the variables used in the GWCR in a representative population sample, a population survey of adults was conducted between May and June 2011 by USUMA, a commercial institute specialized in market, opinion, and social research. For this purpose, participants aged between 18 and 65 years were selected from the general German population from different regions by random digit dialing followed by computer-assisted telephone interviews. Similar to the GWCR, participants were then asked to complete questionnaires by choosing between the Web or paper-and-pencil version (14). A total of 2,286 men and women were recruited for the purpose of this study. About 157 individuals had to be excluded because of missing values and missing weight-related measures, respectively, leaving 2,129 participants for the analyses. All participants were visited in-person and informed about the study procedures by a trained research assistant. They also received a written explanation of the study including information on data management and provided oral informed consent prior to assessment. Oral consent is common in survey research in Germany. The ethical guidelines of the International Code of Marketing and Social Research Practise by the
2
Obesity | VOLUME 00 | NUMBER 00 | MONTH 2015
Weight Loss Maintenance Feller et al.
International Chamber of Commerce and the European Society for Opinion and Marketing Research were followed.
Measures Besides age and sex, the following socio demographic characteristics were assessed: living in a partnership (yes vs. no), being employed (yes vs. no), having an academic degree (yes vs. no). Based on previous literature (1–11) questions assessing various aspects of eating and weighing habits were applied. These included eating frequency and regularity (mean eating occasions per day; consumption of hot meals, breakfast, and fast-food), location of eating (sum of days with different occasions of eating out-of-home), as well as current weighing frequency (from 1 5 “several times daily” to 7 5 “never”). Eating consistency was determined by the ratio of mean eating occasions on weekdays and weekends. Ratios being closer to 1 reflect a higher consistency during the whole week (2). Body height as well as current and maximum weights were assessed by self-report for calculation of body mass index (BMI, kg/m2). Participants were asked how often they had intentionally lost weight (more than 5 kg). The self-reported number of intentional weight loss attempts was used as a measure of weight cycling. Even though no information was available on weight regain following each weight loss, the assumption of at least partial weight regain is supported by other studies (15). To assess non-normative eating behaviors and eating-related psychopathology we used diagnostic items for binge eating disorder (BED) and bulimia nervosa (BN) of the German version of the Eating Disorder Examination-Questionnaire (EDE-Q) (16,17). These items included (1) the importance of shape and weight for self-evaluation (“Over the past four weeks, has your shape/weight influenced how you feel about (judge, think, evaluate) yourself as a person?”), which is rated on a 7-point forced-choice format (0 5 no importance, 6 5 supreme importance), (2) binge eating episodes defined according to DSM-5 criteria (18) (eating an objectively large amount of food with a sense of loss of control), and (3) compensatory behaviors including self-induced vomiting, laxative and diuretic misuse, driven exercising, and 24-hour fasting. Binge eating and any compensatory behaviors were dichotomized for any occurrence ( 1 episode vs. 0 episodes) over the past 28 days. In addition, binge eating frequencies of 4 episodes over the past 28 days and 4 episodes per month over the past 3 months were calculated which corresponds with the DSM-5 frequency requirement for BED and BN (18). With respect to the importance of shape and weight, a composite mean shape/weight over evaluation score was created consistent with prior studies because of high correlations between the two items (19). A clinical cutoff score of 4 was used indicating an at least moderate importance of shape and weight evaluation (16,19). Depressive and somatic symptoms were assessed with subscales of the German version of the Patient Health Questionnaire (PHQ-D) (20–22). The Patient Health Questionnaire depression severity scale (PHQ-9) is a standard tool for assessing depressive symptoms according to DSM-IV-TR. Participants were asked to rate their answers on a 4-point scale from 0 (“not at all”) to 3 (“nearly every day”). The Patient Health Questionnaire somatic symptom severity scale (PHQ15) assesses the most common physical complaints such as stomachaches or headaches. Each symptom is scored from 0 (“not bothered at
www.obesityjournal.org
Original Article
Obesity
EPIDEMIOLOGY/GENETICS
all”) to 2 (“bothered a lot”). For both scales, total sum scores were calculated, for which higher values indicate more severe symptoms. For the PHQ-9 an algorithm is available allowing to calculate the presence of a major depressive episode (MDE). The internal consistency (Cronbach’s a) of both scales was acceptable (PHQ-9: a 5 0.84, PHQ-15: a 5 0.76). Finally, the PHQ-D asks about level of distress (“In the last 4 weeks, how much have you been bothered by worrying about your health?”). Answer possibilities were scored from 0 (“not bothered at all”) to 2 (“bothered a lot”).
Statistical analysis Characteristics of participants of the GWCR and those of the population-based survey are presented by means (6 SD) for continuous variables and by n (%) for categorical variables. Differences between groups were assessed by v2 tests and Wilcoxon tests. To compare both samples, logistic regression models with “sample” as the dependent variable were conducted. Odds ratios (ORs) and confidence intervals (95% CIs) were determined based on the calculated effect estimates. To account for possible confounding effects based on socio demographic differences, multiple adjusted models were used. The first model included age and sex as covariates only. The second model was additionally adjusted for employment status, education, and partnership. For this model P-values were calculated and corrected by false discovery rate to avoid problems regarding multiple testing. In a third model, mutual adjustment was conducted by entering all variables simultaneously to investigate the independence of the observed associations. All analyses were performed with SAS statistical software (SAS Enterprise Guide version 6.1; SAS Institute, Cary, North Carolina, USA). Statistical significance level was set at P < 0.05.
Results The entire study population is described in Table 1. GWCR participants were more often women, slightly older, better educated, more often employed, and more often living in a partnership compared to participants in the general population sample. Although current BMI did not differ between groups, GWCR participants reported a higher maximum BMI and a higher frequency of weight cycling compared to participants in the general population sample. GWCR participants reported a higher eating frequency per day but ate fewer hot meals. These individuals also ate out of home more often compared to participants in the general population sample. No differences were observed for breakfast skipping, eating consistency between weekdays and weekends, and fast-food consumption between samples. In addition, GWCR participants reported a higher frequency of weighing themselves compared to the general population sample. Once daily weighing occurred in 44% of the GWCR participants but only in 16% of the general population, the numbers for weighing once weekly were 11% vs. 17%. As shown in Table 1, GWCR participants reported more binge eating and more compensatory behaviors than the population sample. Furthermore, GWCR participants revealed greater importance of shape or weight. The clinical cutoff score of 4 occurred in 54.9% of GWCR participants and in 20.0% of general population participants. Finally, GWCR participants were significantly more worried about their health, but revealed lower scores on somatic symptoms. No difference was found for depressive symptoms. A major
www.obesityjournal.org
depressive episode (MDE) was found in 5% of GWCR participants and 3% of the population based sample. The results of the three adjusted logistic regression models are presented in Table 2. In the age- and sex-adjusted model (model 1), GWCR participants had a higher eating frequency per day, a higher frequency of eating out, a higher weighing frequency, a higher occurrence of binge eating and compensatory behaviors, and a higher importance of shape and weight for self-evaluation compared to the population sample. Eating hot meals and the occurrence of somatic symptoms were more frequent in the general population sample compared to the GWCR sample. After controlling for all socio demographic variables (model 2) the odds ratios remained quite similar except for worrying about health and depression which were now also found to be significantly higher in GWCR participants compared to the population sample. Correction for multiple testing did not diminish the associations. Similarly, after mutual adjustment (model 3), the reported associations slightly altered in strength but persisted completely. Eating frequency consistency between weekdays and weekends as well as eating breakfast or fast-food showed no differences between the two samples in either model.
Discussion Overall, the successful WLM of the GWCR differed from the general population in important aspects of eating and weighing habits and non-normative eating behaviors as well as eating-related and general psychopathology. These findings were robust against controlling for socio demographic variables, controlling for multiple testing, and mutual adjustment for all variables.
Self-weighing and eating frequency Successful WLM from the GWCR reported weighing themselves more frequently and indicated a larger daily eating frequency in comparison to the representative general population sample. However, no differences were found regarding eating consistency across weekdays and weekends. Regular self-weighing is a useful method to promote weight loss and maintenance, as shown in cohort studies and randomizedcontrolled trials (1,23–25). The potential efficacy of consistent selfmonitoring of weight has been based on self-regulation theory. Eating frequency has been negatively related to BMI in some (26) but not all studies (27), whereas dieting consistency has been shown to be positively associated with weight loss maintenance (2,28). Eating more frequently and maintaining a consistent diet regimen across the week may help to control hunger and decrease the chance of overeating. However, a review of controlled feeding studies suggests that increased eating frequency has minimal, if any, impact on appetite control and food intake. Rather, reduced eating frequency seems to negatively affect appetite control (29). Overall, participants from both cohorts exhibited a high eating frequency and diet consistency and the differences, even though significant, were small.
Eating out and other eating habits The frequency of hot meal consumption was lower and eating-outof-home occurred more often in GWCR participants compared to
Obesity | VOLUME 00 | NUMBER 00 | MONTH 2015
3
Obesity
Weight Loss Maintenance Feller et al.
TABLE 1 Characteristics of German Weight Control Registry participants and a representative German population sample
German Weight Control Registry
N Socio demographic characteristics Sex (women vs. men) Age (years) Employment (yes vs. no) Academic degree (yes vs. no) Partnership (yes vs. no) Anthropometric characteristics Current BMI (kg/m2) Maximum BMI (kg/m2) Weight cycling (sum of intentional weight loss attempts) Eating and weighing habits Weighing frequency (from 1 5 never to 7 5 several times daily) Eating frequency (meals and snacks per day) Eating frequency consistency (weekday-weekend ratio) Breakfast (days per week) Hot meals (days per week) Eating-out-of-home (sum of days per week) Fast-food (days per week) Eating-related psychopathology Shape and weight over evaluation (from 0 5 no importance to 6 5 supreme importance) Compensatory behaviors during the last 28 days (yes vs. no) Binge eating during the last 28 days (yes vs. no) Binge eating occurring 4 times during the last 28 days (yes vs. no) Binge eating occurring 4 times per month during the last 3 months (yes vs. no) General psychopathology Bothered by worrying about health (1 5 not bothered at all, 2 5 bothered a little, 3 5 bothered a lot) PHQ depression severity scale (PHQ-9, total score 0–27) PHQ somatic symptom severity scale (PHQ-15, total score 0–30)
Mean or %
494 494 489 492 490
60.7 47.62 76.9 46.8 81.6
494 494 494
25.69 33.20 5.07
491 486 486 486 487 403 428
SD
Population-based survey
N
Mean or %
SD
P-value 0.01a 0.008b 0.003a
