PEDIATRICOBESITY ORIGINALRESEARCH
Extremely obese children respond better than extremely obese adolescents to lifestyle interventions C. Knop, V. Singer, Y. Uysal, A. Schaefer, B. Wolters and T. Reinehr Department of Pediatric Endocrinology, Diabetes, and Nutrition Medicine, Vestische Hospital for Children and Adolescents, University of Witten, Herdecke, Germany Received 17 July 2013; revised 15 October 2013; accepted 20 October 2013
What is already known about this subject
What this study adds
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Lifestyle intervention is regarded as therapy of choice in obese children and adolescents. It is unclear whether extremely obese children and adolescents respond to lifestyle intervention.
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Extremely obese children respond better than obese children to a lifestyle intervention. In contrast, most extremely obese adolescents achieved no weight loss in lifestyle intervention suggesting that other treatment approaches are needed for them.
Summary Background: There are conflicting results of treating extreme obesity in childhood by lifestyle interventions in the literature.
Methods: We analysed the outcome of a 1-year lifestyle intervention in an intention-to-treat approach in 1291 children (mean age 11.0 ± 2.5 years, mean body mass index [BMI] 27.5 ± 4.7 kg m−2, 55.8% female, 62.4% obese, 37.6% extremely obese (defined by BMI-SDS >2.3) at end of intervention and 1 year later. Results: The mean BMI-SDS reduction was −0.20 ± 0.32 at end of intervention and −0.14 ± 0.37 1 year after end of intervention compared to baseline (comparing intervention vs. 1 year later P = 0.010). Extremely obese children ≤10 years demonstrated a significantly greater BMI-SDS reduction than obese children ≤10 years (−0.24 ± 0.38 vs. −0.16 ± 0.38, P = 0.021). Extremely obese adolescents >10 years demonstrated a significantly lower BMI-SDS reduction compared to obese adolescents >10 years (−0.05 ± 0.30 vs. −0.15 ± 0.39, P < 0.001). Comparing the BMI-SDS reduction between obese children 10 years revealed no significant difference (P = 0.195) in contrast to the comparison between extremely obese children 10 years (P < 0.001). The same findings were observed in the follow-up period after the end of intervention. Conclusions: Our study demonstrated an encouraging effect of lifestyle intervention in extremely obese children ≤10 years at the end of intervention and 1 year later, but only a limited effect in extremely obese adolescents >10 years. Keywords: Adolescents, age, children, extreme obesity, weight loss.
Address for correspondence: Professor Dr T Reinehr, Head of the Department of Pediatric Endocrinology, Diabetes, and Nutrition Medicine, Vestische Hospital for Children and Adolescents, University of Witten/Herdecke, Dr. F. Steiner Str. 5, 45711 Datteln, Germany. E-mail: [email protected] © 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14 Funding source: Thomas Reinehr: received grant support from of the German Ministry of Education and Research (Bundesministerium für Bildung und Forschung Obesity network: grant number 01 01GI1120A and 01GI 1120B). Financial disclosure statement: nothing to disclose. Study registration: This study is registered at clinicaltrials.gov (NCT00435734).
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Introduction
Recruitment
Obesity in childhood and adolescence is an overwhelming health problem worldwide (1,2). Obese children and adolescents are at risk for comorbidities of obesity such as hypertension, dyslipidaemia and type 2 diabetes (3,4). Lifestyle intervention is regarded as therapy of choice in obese children (5–7) even if the outcome of lifestyle intervention is very heterogeneous in clinical practice (8,9). Frequently obese and extremely obese children are summarized in clinical trials not allowing to assess whether extremely obese children respond to lifestyle intervention comparable to obese children (5,6). However, the effectiveness in extremely obese adolescents is discussed critically (8). The dropout rate has been reported to increase in extremely obese adolescents participating in a lifestyle intervention (10). Furthermore, Danielsson et al. demonstrated no clinically relevant weight loss in extremely obese adolescents (11). In the same study cohort, younger age was associated with better outcome in the lifestyle intervention (12). Therefore, the question arises whether age or degree of overweight is a more relevant predictor of weight loss. Conversely, Nemet et al. demonstrated encouraging results of a combined lifestyle intervention in severely obese prepubertal children (13). These controversial findings may point towards an impact of age on the outcome of lifestyle interventions in extremely obese children and adolescents. Because of the very limited available studies of extremely obese children and adolescents participating in lifestyle interventions and the lack of studies with follow-up, we analysed the effect of extreme obesity and age on the outcome of a lifestyle intervention both at end of intervention and 1 year later. We hypothesize that extremely obese children respond better to lifestyle interventions compared to extremely obese adolescents.
Families with obese children were informed by their house doctors concerning the lifestyle intervention ‘Obeldicks’. The families presented than at the five outpatient obesity clinics in West Germany offering this lifestyle intervention. The treatment centres followed a standardized recruitment and treatment protocol (for details see (14)). All therapists have been educated by a structured training programme (15).
Materials and methods The local ethics committee of the University of Witten/Herdecke approved this study. Written informed consent was obtained from all subjects and their parents according to the declaration of Helsinki. We studied prospectively all children and adolescents who were presented to treat their obesity in the years 2001 to 2011 at the five treatment centres in West Germany offering the 1-year lifestyle intervention ‘Obeldicks’. We examined the children both at end of 1-year intervention and 1 year later (= 2 years after baseline).
Inclusion and exclusion criteria Children on medical therapy or with endocrine, genetic or metabolic disorders were excluded from the study. Inclusion criteria were age 6 to 15 years, body mass index (BMI) > 97th percentile, visit of school and prove of motivation to change lifestyle behaviour. Motivation was proven by the following criteria: (i) the children > 8 years had to fill out a questionnaire on their eating and exercise habits, (ii) their parents had to fill out a corresponding questionnaire on the eating and exercise habits of their child, (iii) the families had to perform a 3-day dietary record, and (iv) participation in local exercise groups for obese children for at least 8 weeks before start of intervention was required. Motivation was assumed when all of these criteria were fulfilled independently of the given answers in the questionnaires or the results of the dietary records (16).
Intervention The 1-year lifestyle intervention ‘Obeldicks’ has been described in detail elsewhere (14,17). The aim of the intervention was to reduce overweight. Briefly, this outpatient intervention programme was based on physical activity, nutrition education and behaviour therapy including the individual psychological care of the child and his/her family. An interdisciplinary team of paediatricians, diet-assistants, psychologists and exercise physiologists was responsible for the training. In children ≤ 10 years, girls and boys were treated together, in older children girls and boys were treated separated to gender. The 1-year training programme was divided into three phases: In the intensive phase (3 months), the children took part in the nutritional course and in the eating-behaviour course in six group sessions each lasting for 1.5 hours. At the same time, the parents were invited to attend six parents’ evenings. In the establishing phase (6 months), individual psychological family therapy was provided (30 min month−1). In the last phase of the programme (accompanying the families back to their
© 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14
everyday lives) (3 months), further individual care was possible, if and when necessary. The exercise therapy took place once a week during the whole year. The nutritional course was based on the prevention concept of the ‘Optimized mixed diet’. In contrast to the present-day diet of children in Germany with a fat-content of 38% of energy intake, 13% proteins and 49% carbohydrates including 14% sugar, the ‘Optimized mixed diet’ was both fat and sugar reduced and contained 30% fat, 15% proteins and 55% carbohydrates including 5% sugar (14). Instead of counting calories, the children followed a ‘traffic-light system’ when selecting their food.
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years. This cut-off point was used since children ≤ 10 years are usually pre-pubertal in contrast to older children. Furthermore, the intervention differed between children younger and older 10 years. In children ≤ 10 year girls and boys were treated together, in older children girls and boys were treated in separate groups. Furthermore, we performed a separate analysis in the children with complete follow-up (per-protocol analysis). A P-value 2.3 in concordance with the German guidelines (21). Success in lifestyle intervention was defined as reduction of >0.25 BMI-SDS according to guidelines and references (6,22,23).
A total of 1291 children (mean age 11.0 ± 2.5 years, mean BMI 27.5 ± 4.7 kg m−2, 55.8% female, 62.4% obese, 37.6% extremely obese) were included (Fig. 1). The number of dropouts did not differ significantly between the children separated to age < 10/ > 10 years and obese/extremely obese children (P = 0.601). None of the children who had dropped out prior to the end of intervention was remeasured at 2-year follow-up. The children did not differ according to age, degree of overweight (BMI-SDS) or gender at baseline between the different treatment centres. The baseline data and changes in the 2-year period concerning weight status are demonstrated in Table 1. The lost follow-up rate was 21% at end of intervention, while 34% reduced their BMI-SDS >0.25. Two years after baseline, the lost follow-up rate was 39% and the success rate defined by BMISDS reduction >0.25 was 27%.
Statistical methods
Intention-to-treat analyses
Statistical analyses were carried out with Winstat for ExelTM (R. Fitch Software, Krozingen, Germany). All analyses were performed with the intention-to-treat approach. The BMI-SDS of children without follow-up was set back to baseline. Children with complete follow-up and an increase of their BMI-SDS were not set to baseline. All variables were normally distributed as tested by the Kolmogorov–Smirnov test. Comparisons were performed by chi-square test, ANOVA with Bonferroni adjustment, as well as Student’s t-test for unpaired and paired observations as appropriate. Changes of BMI-SDS at end of intervention and 1 year later were included as dependent variables in multiple regression analyses with the independent variables baseline age, baseline BMISDS and gender. Gender was integrated as categorical variables in these models. All analyses were also performed separated to children 10
Children ≤10 years demonstrated a significant greater BMI-SDS reduction (P < 0.001) as compared with adolescents >10 years both at end of intervention and 1 year after end of intervention (see Table 1). Extremely obese participants did not differ significantly from obese participants in respect to changes of BMI-SDS at end of intervention and 1 year later (Table 1). In multiple linear regression analyses, age at baseline was negatively related to BMI-SDS reduction at end of intervention and BMI-SDS reduction 2 years after baseline (Table 2). The changes of BMI-SDS during the intervention period separated to age of children and degree of overweight are presented in Fig. 2. Extremely obese children ≤10 years demonstrated a significant greater BMI-SDS reduction than obese children ≤10 years, while extremely obese adolescents >10 years
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Figure 1 Flow chart of the study.
Table 1 BMI-SDS and its changes in the 2-year period separated to age and degree of overweight (intention-to-treat approach)
All children (n = 1291) ≤10 years (n = 496) >10 years (n = 795) Obese (n = 805) Extremely obese (n = 486)
Baseline BMI-SDS
Change of BMI-SDS during 1-year intervention
Change of BMI-SDS P-value base- P-value base- P-value 1 year line compared line compared compared to between baseline to 2 years 2 years and 1 year after end to 1 year of intervention (= 2 years after baseline)
2.38 ± 0.47 2.46 ± 0.50 2.32 ± 0.45 2.05 ± 0.28 2.86 ± 0.30
−0.20 ± 0.32 −0.26 ± 0.35 −0.16 ± 0.31 −0.20 ± 0.33 −0.19 ± 0.33
−0.14 ± 0.37 −0.20 ± 0.38 −0.12 ± 0.37 −0.15 ± 0.39 −0.14 ± 0.35
10 years demonstrated a significant greater BMI-SDS reduction compared to extremely obese children >10 years both at end of intervention (P < 0.001) and 2 years after baseline (P < 0.001) (Table 3). Comparing the BMI-SDS reduction during the intervention period between obese children 10 years revealed no significant difference (P = 0.262) in contrast to the comparison between extremely obese children 10 years (P < 0.001). Comparing the BMI-SDS reduction in the 2-year follow-up between obese children 10 years revealed no significant difference (P = 0.912) in contrast to the comparison between extremely obese children 10 years (P < 0.001). The success rate (defined as BMI-SDS reduction >0.25) in the intervention period was 59.8% in extremely obese children and 47.7% in obese children ≤10 years. Only 27.1% of the extremely obese adolescents (age >10 years) reduced their BMI-SDS >0.25, while 41.5% of the obese adolescents (age >10 years) demonstrated a reduction of BMI-SDS >0.25 during the intervention period. In multiple linear regression analyses, age was significantly (P < 0.001) related to changes of BMI-SDS at end of intervention (β-coefficient = −0.03 ± 0.01, r2 = 0.05) and to changes of BMI-SDS 2 years after baseline (β-coefficient = −0.04 ± 0.01, r2 = 0.05), but not to gender or baseline BMI-SDS.
Discussion To the best of our knowledge, this is the first study assessing the impact of age on the outcome of a 1-year multidisciplinary outpatient lifestyle intervention in extremely obese children and adolescents. The mean reduction of BMI-SDS during lifestyle intervention and the success rate defined by BMISDS reduction >0.25 in the entire cohort was similar to previous studies (6–9,24–26). According to the literature, younger age was associated with greater reduction of BMI-SDS (6,7,24,26,27). Interestingly, extremely obese children ≤10 years demonstrated a significantly greater BMI-SDS reduction in our study compared with obese children ≤10 years both at end of 1-year intervention and 1 year after end of inter-
© 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14
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Table 3 Changes of BMI-SDS in the 2-year period separated to age and degree of overweight (per-protocol approach analysing only children with complete follow-up)
Obese children ≤10 years Extremely obese children ≤10 years Obese children >10 years Extremely obese children >10 years
vention. Furthermore, the highest success rate was seen in extremely obese children ≤10 years. These findings fit well to the study of Nemet et al. reporting encouraging results of a combined lifestyle intervention in severely obese pre-pubertal children (13). On the other side, extremely obese adolescents >10 years showed the lowest success rate and a significantly lower BMI-SDS reduction both at end of intervention and 1 year later compared to obese adolescents. These observations are in concordance with the study of Danielsson et al. showing no clinical relevant weight loss in extremely obese adolescents (11). In conclusion, lifestyle intervention is much more effective in extremely obese children than in extremely obese adolescents, while the success rate and BMI-SDS reduction were similar in obese children and obese adolescents. As in our study, the success rate was only 20% in extremely obese adolescents; this suggests that other interventions (for example drugs or bariatric surgery) beside lifestyle interventions are necessary in the majority of adolescents with severe obesity if we cannot improve the lifestyle intervention for this target group. The reasons for this difference concerning effectiveness of lifestyle intervention between extremely obese children and adolescents remain unclear. While in the last decade lifestyle interventions focused on children, it becomes quite clear in recent years that interventions involving parents are more effective than interventions solely for obese children (6,7,26,28–31). Maybe, the limited effect of parents on health behaviour habits of adolescents explains at least the disappointing findings in lifestyle intervention of extremely obese adolescents (32). In contrast, other studies report that even adolescents mimic the health behaviour of their parents (33). However, obese children did not differ significantly in respect to BMI-SDS reduction during lifestyle intervention from obese adolescents. This finding points against a simple age effect in lifestyle interventions. It can be speculated that the worse outcome in extremely obese adolescents is also caused by certain characteristics of these patients and their
Change of BMI-SDS during 1-year intervention
Change of BMI-SDS between baseline and 1 year after end of intervention (= 2 years after baseline)
−0.28 ± 0.35 −0.36 ± 0.36 −0.26 ± 0.35 −0.12 ± 0.30
−0.25 ± 0.46 −0.38 ± 0.41 −0.26 ± 0.23 −0.10 ± 0.48
families (e.g. lack of psychosocial support and parenting skills), by a decline in the motivation for lifestyle changes, or by inadvertent constraints to therapy adherence (34). Indeed, we found the highest dropout rate in extremely obese adolescents according to the literature reporting an increased dropout rate in extremely obese adolescents participating in a lifestyle intervention (10). In multiple linear regression analyses, baseline BMI-SDS was not significantly related to changes of BMI-SDS at end of intervention or at follow-up. This finding can be explained by summing children < 10 years and > 10 years in these analyses. Extremely obese children (≤10 years) responded better than obese children (≤10 years), while extremely obese adolescents (>10 years) responded poorer than obese adolescents (>10 years).
Strengths and limitations of the study The strengths of this study are the large study sample, the intention-to-treat approach, the multicentre design, the analysis of obese children naive to drugs and the follow-up period after end of treatment. However, some potential limitations of our study have to be considered. First, BMI percentiles were used to classify overweight. Although BMI is a good measure for overweight, one needs to be aware of its limitation as an indirect measure of fat mass. Furthermore, success was defined by change of BMI-SDS and not of change of fat mass. Using the BMI-SDS to describe weight changes has some limitations (35) probably also explaining in part why the extremely obese ≤10 years might reduce their degree of overweight greater than the obese children. Second, we are not able to differentiate the effect of diet and increased physical exercise on weight loss because of our study protocol. Furthermore, the effects of dieting and increased physical activity probably strengthened each other. Third, we cannot exclude different socio-economic backgrounds or lifestyle habits in the participants of the intervention programme. Fourth, the children were
© 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14
not randomized to different treatment centres and we have no untreated control group. However, for ethical reasons, it seems difficult to prevent obese children from a potential effective intervention. One might argue that the changes of BMI-SDS in our study might occur even without intervention. Indeed, population-based studies have reported a slight decrease in BMI-SDS in overweight not treatmentseeking children (36). In contrast, our participants were obese and extremely obese as well as treatment seeking. Without intervention, obese and extremely obese children and adolescents tend to increase their weight (37,38). Moreover, the prevalence of extremely obese children and adolescents is increasing in the United States pointing against spontaneous normalization of weight (4,39). Furthermore, we have previously reported the changes of BMI-SDS in treatment-seeking obese children and adolescents without the lifestyle intervention ‘Obeldicks’ (22,40): The control group of obese children in these studies demonstrated a slight increase of BMI-SDS. Fifth, we have to keep in mind that the changes of BMI-SDS represent in part the statistic phenomenon regression to the mean. As this effect is likely larger in the extremely obese compared with obese children and adolescents, this phenomenon seem not to explain the disappointing results in extremely obese adolescents. Finally, the high loss to follow-up rate which is typical for lifestyle interventions in obese children and adolescents is an important limitation. If the participants with lost to follow-up increased their BMI-SDS over the 2 years, the effect of our lifestyle intervention would be overestimated because of our statistical approach setting BMI-SDS back to baseline in participants with lost to follow-up. However, all of participants with loss to follow-up were categorized as treatment failures in the intention-to-treat approach. In summary, our study demonstrated an encouraging effect of lifestyle intervention in extremely obese children ≤10 years both at end of intervention and 1 year later, but only a limited effect in extremely obese adolescents >10 years. Therefore, other therapeutic approaches seem to be needed in severe obese adolescents if we are not able to improve lifestyle programmes for extremely obese adolescents.
Conflict of interest statement All authors have no conflicts of interest.
Acknowledgement We thank the participating children and adolescents.
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16. Reinehr T, Brylak K, Alexy U, Kersting M, Andler W. Predictors to success in outpatient training in obese children and adolescents. Int J Obes Relat Metab Disord 2003; 27: 1087–1092. 17. Reinehr T, Kleber M, Lass N, Toschke AM. Body mass index patterns over 5 y in obese children motivated to participate in a 1-y lifestyle intervention: age as a predictor of long-term success. Am J Clin Nutr 2010; 91: 1165–1171. 18. Cole TJ. The LMS method for constructing normalized growth standards. Eur J Clin Nutr 1990; 44: 45–60. 19. Kromeyer-Hauschild K, Wabitsch M, Geller F, et al. Percentiles of body mass index in children and adolescents evaluated from different regional German studies. Monatsschr Kinderheilkd 2001; 149: 807–818. 20. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000; 320: 1240– 1243. 21. Guidelines of the German working group on obese children and adolescents. [WWW document]. URL http:// www.a-g-a.de/Leitlinie.pdf (accessed July 2013). 22. Reinehr T, Kleber M, Toschke AM. Lifestyle intervention in obese children is associated with a decrease of the metabolic syndrome prevalence. Atherosclerosis 2009; 207: 174–180. 23. Ford AL, Hunt LP, Cooper A, Shield JP. What reduction in BMI SDS is required in obese adolescents to improve body composition and cardiometabolic health? Arch Dis Child 2010; 95: 256–261. 24. Katz DL, O’Connell M, Njike VY, Yeh MC, Nawaz H. Strategies for the prevention and control of obesity in the school setting: systematic review and meta-analysis. Int J Obes (Lond) 2008; 32: 1780–1789. 25. Savoye M, Nowicka P, Shaw M, et al. Long-term results of an obesity program in an ethnically diverse pediatric population. Pediatrics 2011; 127: 402–410. 26. McGovern L, Johnson JN, Paulo R, et al. Clinical review: treatment of pediatric obesity: a systematic review and meta-analysis of randomized trials. J Clin Endocrinol Metab 2008; 93: 4600–4605. 27. Reinehr T, Hoffmeister U, Mann R, et al. Medical care of overweight children under real-life conditions: the German BZgA observation study. Int J Obes (Lond) 2009; 33: 418–423. 28. Young KM, Northern JJ, Lister KM, Drummond JA, O’Brien WH. A meta-analysis of family-behavioral weight-
loss treatments for children. Clin Psychol Rev 2007; 27: 240–249. 29. Casazza K, Fontaine KR, Astrup A, et al. Myths, presumptions, and facts about obesity. N Engl J Med 2013; 368: 446–454. 30. Magarey AM, Perry RA, Baur LA, et al. A parent-led family-focused treatment program for overweight children aged 5 to 9 years: the PEACH RCT. Pediatrics 2011; 127: 214–222. 31. Okely AD, Collins CE, Morgan PJ, et al. Multi-site randomized controlled trial of a child-centered physical activity program, a parent-centered dietary-modification program, or both in overweight children: the HIKCUPS study. J Pediatr 2010; 157: 388–394, 394.e1. 32. Tome G, Matos M, Simoes C, Diniz JA, Camacho I. How can peer group influence the behavior of adolescents: explanatory model. Glob J Health Sci 2012; 4: 26–35. 33. Cislak A, Safron M, Pratt M, Gaspar T, Luszczynska A. Family-related predictors of body weight and weightrelated behaviours among children and adolescents: a systematic umbrella review. Child Care Health Dev 2012; 38: 321–331. 34. Elfhag K, Rossner S. Who succeeds in maintaining weight loss? A conceptual review of factors associated with weight loss maintenance and weight regain. Obes Rev 2005; 6: 67–85. 35. Woo JG. Using body mass index Z-score among severely obese adolescents: a cautionary note. Int J Pediatr Obes 2009; 4: 405–410. 36. Williamson DA, Han H, Johnson WD, Stewart TM, Harsha DW. Longitudinal study of body weight changes in children: who is gaining and who is losing weight. Obesity (Silver Spring) 2011; 19: 667–670. 37. Freedman DS, Shear CL, Burke GL, et al. Persistence of juvenile-onset obesity over eight years: the Bogalusa Heart Study. Am J Public Health 1987; 77: 588–592. 38. Freedman DS, Mei Z, Srinivasan SR, Berenson GS, Dietz WH. Cardiovascular risk factors and excess adiposity among overweight children and adolescents: the Bogalusa Heart Study. J Pediatr 2007; 150: 12–17. 39. Skelton JA, Cook SR, Auinger P, Klein JD, Barlow SE. Prevalence and trends of severe obesity among US children and adolescents. Acad Pediatr 2009; 9: 322–329. 40. Reinehr T, Kersting M, Alexy U, Andler W. Long-term follow-up of overweight children: after training, after a single consultation session, and without treatment. J Pediatr Gastroenterol Nutr 2003; 37: 72–74.
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Extremely obese children respond better than extremely obese adolescents to lifestyle interventions C. Knop, V. Singer, Y. Uysal, A. Schaefer, B. Wolters and T. Reinehr Department of Pediatric Endocrinology, Diabetes, and Nutrition Medicine, Vestische Hospital for Children and Adolescents, University of Witten, Herdecke, Germany Received 17 July 2013; revised 15 October 2013; accepted 20 October 2013
What is already known about this subject
What this study adds
•
•
•
Lifestyle intervention is regarded as therapy of choice in obese children and adolescents. It is unclear whether extremely obese children and adolescents respond to lifestyle intervention.
•
Extremely obese children respond better than obese children to a lifestyle intervention. In contrast, most extremely obese adolescents achieved no weight loss in lifestyle intervention suggesting that other treatment approaches are needed for them.
Summary Background: There are conflicting results of treating extreme obesity in childhood by lifestyle interventions in the literature.
Methods: We analysed the outcome of a 1-year lifestyle intervention in an intention-to-treat approach in 1291 children (mean age 11.0 ± 2.5 years, mean body mass index [BMI] 27.5 ± 4.7 kg m−2, 55.8% female, 62.4% obese, 37.6% extremely obese (defined by BMI-SDS >2.3) at end of intervention and 1 year later. Results: The mean BMI-SDS reduction was −0.20 ± 0.32 at end of intervention and −0.14 ± 0.37 1 year after end of intervention compared to baseline (comparing intervention vs. 1 year later P = 0.010). Extremely obese children ≤10 years demonstrated a significantly greater BMI-SDS reduction than obese children ≤10 years (−0.24 ± 0.38 vs. −0.16 ± 0.38, P = 0.021). Extremely obese adolescents >10 years demonstrated a significantly lower BMI-SDS reduction compared to obese adolescents >10 years (−0.05 ± 0.30 vs. −0.15 ± 0.39, P < 0.001). Comparing the BMI-SDS reduction between obese children 10 years revealed no significant difference (P = 0.195) in contrast to the comparison between extremely obese children 10 years (P < 0.001). The same findings were observed in the follow-up period after the end of intervention. Conclusions: Our study demonstrated an encouraging effect of lifestyle intervention in extremely obese children ≤10 years at the end of intervention and 1 year later, but only a limited effect in extremely obese adolescents >10 years. Keywords: Adolescents, age, children, extreme obesity, weight loss.
Address for correspondence: Professor Dr T Reinehr, Head of the Department of Pediatric Endocrinology, Diabetes, and Nutrition Medicine, Vestische Hospital for Children and Adolescents, University of Witten/Herdecke, Dr. F. Steiner Str. 5, 45711 Datteln, Germany. E-mail: [email protected] © 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14 Funding source: Thomas Reinehr: received grant support from of the German Ministry of Education and Research (Bundesministerium für Bildung und Forschung Obesity network: grant number 01 01GI1120A and 01GI 1120B). Financial disclosure statement: nothing to disclose. Study registration: This study is registered at clinicaltrials.gov (NCT00435734).
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Introduction
Recruitment
Obesity in childhood and adolescence is an overwhelming health problem worldwide (1,2). Obese children and adolescents are at risk for comorbidities of obesity such as hypertension, dyslipidaemia and type 2 diabetes (3,4). Lifestyle intervention is regarded as therapy of choice in obese children (5–7) even if the outcome of lifestyle intervention is very heterogeneous in clinical practice (8,9). Frequently obese and extremely obese children are summarized in clinical trials not allowing to assess whether extremely obese children respond to lifestyle intervention comparable to obese children (5,6). However, the effectiveness in extremely obese adolescents is discussed critically (8). The dropout rate has been reported to increase in extremely obese adolescents participating in a lifestyle intervention (10). Furthermore, Danielsson et al. demonstrated no clinically relevant weight loss in extremely obese adolescents (11). In the same study cohort, younger age was associated with better outcome in the lifestyle intervention (12). Therefore, the question arises whether age or degree of overweight is a more relevant predictor of weight loss. Conversely, Nemet et al. demonstrated encouraging results of a combined lifestyle intervention in severely obese prepubertal children (13). These controversial findings may point towards an impact of age on the outcome of lifestyle interventions in extremely obese children and adolescents. Because of the very limited available studies of extremely obese children and adolescents participating in lifestyle interventions and the lack of studies with follow-up, we analysed the effect of extreme obesity and age on the outcome of a lifestyle intervention both at end of intervention and 1 year later. We hypothesize that extremely obese children respond better to lifestyle interventions compared to extremely obese adolescents.
Families with obese children were informed by their house doctors concerning the lifestyle intervention ‘Obeldicks’. The families presented than at the five outpatient obesity clinics in West Germany offering this lifestyle intervention. The treatment centres followed a standardized recruitment and treatment protocol (for details see (14)). All therapists have been educated by a structured training programme (15).
Materials and methods The local ethics committee of the University of Witten/Herdecke approved this study. Written informed consent was obtained from all subjects and their parents according to the declaration of Helsinki. We studied prospectively all children and adolescents who were presented to treat their obesity in the years 2001 to 2011 at the five treatment centres in West Germany offering the 1-year lifestyle intervention ‘Obeldicks’. We examined the children both at end of 1-year intervention and 1 year later (= 2 years after baseline).
Inclusion and exclusion criteria Children on medical therapy or with endocrine, genetic or metabolic disorders were excluded from the study. Inclusion criteria were age 6 to 15 years, body mass index (BMI) > 97th percentile, visit of school and prove of motivation to change lifestyle behaviour. Motivation was proven by the following criteria: (i) the children > 8 years had to fill out a questionnaire on their eating and exercise habits, (ii) their parents had to fill out a corresponding questionnaire on the eating and exercise habits of their child, (iii) the families had to perform a 3-day dietary record, and (iv) participation in local exercise groups for obese children for at least 8 weeks before start of intervention was required. Motivation was assumed when all of these criteria were fulfilled independently of the given answers in the questionnaires or the results of the dietary records (16).
Intervention The 1-year lifestyle intervention ‘Obeldicks’ has been described in detail elsewhere (14,17). The aim of the intervention was to reduce overweight. Briefly, this outpatient intervention programme was based on physical activity, nutrition education and behaviour therapy including the individual psychological care of the child and his/her family. An interdisciplinary team of paediatricians, diet-assistants, psychologists and exercise physiologists was responsible for the training. In children ≤ 10 years, girls and boys were treated together, in older children girls and boys were treated separated to gender. The 1-year training programme was divided into three phases: In the intensive phase (3 months), the children took part in the nutritional course and in the eating-behaviour course in six group sessions each lasting for 1.5 hours. At the same time, the parents were invited to attend six parents’ evenings. In the establishing phase (6 months), individual psychological family therapy was provided (30 min month−1). In the last phase of the programme (accompanying the families back to their
© 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14
everyday lives) (3 months), further individual care was possible, if and when necessary. The exercise therapy took place once a week during the whole year. The nutritional course was based on the prevention concept of the ‘Optimized mixed diet’. In contrast to the present-day diet of children in Germany with a fat-content of 38% of energy intake, 13% proteins and 49% carbohydrates including 14% sugar, the ‘Optimized mixed diet’ was both fat and sugar reduced and contained 30% fat, 15% proteins and 55% carbohydrates including 5% sugar (14). Instead of counting calories, the children followed a ‘traffic-light system’ when selecting their food.
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years. This cut-off point was used since children ≤ 10 years are usually pre-pubertal in contrast to older children. Furthermore, the intervention differed between children younger and older 10 years. In children ≤ 10 year girls and boys were treated together, in older children girls and boys were treated in separate groups. Furthermore, we performed a separate analysis in the children with complete follow-up (per-protocol analysis). A P-value 2.3 in concordance with the German guidelines (21). Success in lifestyle intervention was defined as reduction of >0.25 BMI-SDS according to guidelines and references (6,22,23).
A total of 1291 children (mean age 11.0 ± 2.5 years, mean BMI 27.5 ± 4.7 kg m−2, 55.8% female, 62.4% obese, 37.6% extremely obese) were included (Fig. 1). The number of dropouts did not differ significantly between the children separated to age < 10/ > 10 years and obese/extremely obese children (P = 0.601). None of the children who had dropped out prior to the end of intervention was remeasured at 2-year follow-up. The children did not differ according to age, degree of overweight (BMI-SDS) or gender at baseline between the different treatment centres. The baseline data and changes in the 2-year period concerning weight status are demonstrated in Table 1. The lost follow-up rate was 21% at end of intervention, while 34% reduced their BMI-SDS >0.25. Two years after baseline, the lost follow-up rate was 39% and the success rate defined by BMISDS reduction >0.25 was 27%.
Statistical methods
Intention-to-treat analyses
Statistical analyses were carried out with Winstat for ExelTM (R. Fitch Software, Krozingen, Germany). All analyses were performed with the intention-to-treat approach. The BMI-SDS of children without follow-up was set back to baseline. Children with complete follow-up and an increase of their BMI-SDS were not set to baseline. All variables were normally distributed as tested by the Kolmogorov–Smirnov test. Comparisons were performed by chi-square test, ANOVA with Bonferroni adjustment, as well as Student’s t-test for unpaired and paired observations as appropriate. Changes of BMI-SDS at end of intervention and 1 year later were included as dependent variables in multiple regression analyses with the independent variables baseline age, baseline BMISDS and gender. Gender was integrated as categorical variables in these models. All analyses were also performed separated to children 10
Children ≤10 years demonstrated a significant greater BMI-SDS reduction (P < 0.001) as compared with adolescents >10 years both at end of intervention and 1 year after end of intervention (see Table 1). Extremely obese participants did not differ significantly from obese participants in respect to changes of BMI-SDS at end of intervention and 1 year later (Table 1). In multiple linear regression analyses, age at baseline was negatively related to BMI-SDS reduction at end of intervention and BMI-SDS reduction 2 years after baseline (Table 2). The changes of BMI-SDS during the intervention period separated to age of children and degree of overweight are presented in Fig. 2. Extremely obese children ≤10 years demonstrated a significant greater BMI-SDS reduction than obese children ≤10 years, while extremely obese adolescents >10 years
© 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14
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Figure 1 Flow chart of the study.
Table 1 BMI-SDS and its changes in the 2-year period separated to age and degree of overweight (intention-to-treat approach)
All children (n = 1291) ≤10 years (n = 496) >10 years (n = 795) Obese (n = 805) Extremely obese (n = 486)
Baseline BMI-SDS
Change of BMI-SDS during 1-year intervention
Change of BMI-SDS P-value base- P-value base- P-value 1 year line compared line compared compared to between baseline to 2 years 2 years and 1 year after end to 1 year of intervention (= 2 years after baseline)
2.38 ± 0.47 2.46 ± 0.50 2.32 ± 0.45 2.05 ± 0.28 2.86 ± 0.30
−0.20 ± 0.32 −0.26 ± 0.35 −0.16 ± 0.31 −0.20 ± 0.33 −0.19 ± 0.33
−0.14 ± 0.37 −0.20 ± 0.38 −0.12 ± 0.37 −0.15 ± 0.39 −0.14 ± 0.35
10 years demonstrated a significant greater BMI-SDS reduction compared to extremely obese children >10 years both at end of intervention (P < 0.001) and 2 years after baseline (P < 0.001) (Table 3). Comparing the BMI-SDS reduction during the intervention period between obese children 10 years revealed no significant difference (P = 0.262) in contrast to the comparison between extremely obese children 10 years (P < 0.001). Comparing the BMI-SDS reduction in the 2-year follow-up between obese children 10 years revealed no significant difference (P = 0.912) in contrast to the comparison between extremely obese children 10 years (P < 0.001). The success rate (defined as BMI-SDS reduction >0.25) in the intervention period was 59.8% in extremely obese children and 47.7% in obese children ≤10 years. Only 27.1% of the extremely obese adolescents (age >10 years) reduced their BMI-SDS >0.25, while 41.5% of the obese adolescents (age >10 years) demonstrated a reduction of BMI-SDS >0.25 during the intervention period. In multiple linear regression analyses, age was significantly (P < 0.001) related to changes of BMI-SDS at end of intervention (β-coefficient = −0.03 ± 0.01, r2 = 0.05) and to changes of BMI-SDS 2 years after baseline (β-coefficient = −0.04 ± 0.01, r2 = 0.05), but not to gender or baseline BMI-SDS.
Discussion To the best of our knowledge, this is the first study assessing the impact of age on the outcome of a 1-year multidisciplinary outpatient lifestyle intervention in extremely obese children and adolescents. The mean reduction of BMI-SDS during lifestyle intervention and the success rate defined by BMISDS reduction >0.25 in the entire cohort was similar to previous studies (6–9,24–26). According to the literature, younger age was associated with greater reduction of BMI-SDS (6,7,24,26,27). Interestingly, extremely obese children ≤10 years demonstrated a significantly greater BMI-SDS reduction in our study compared with obese children ≤10 years both at end of 1-year intervention and 1 year after end of inter-
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Table 3 Changes of BMI-SDS in the 2-year period separated to age and degree of overweight (per-protocol approach analysing only children with complete follow-up)
Obese children ≤10 years Extremely obese children ≤10 years Obese children >10 years Extremely obese children >10 years
vention. Furthermore, the highest success rate was seen in extremely obese children ≤10 years. These findings fit well to the study of Nemet et al. reporting encouraging results of a combined lifestyle intervention in severely obese pre-pubertal children (13). On the other side, extremely obese adolescents >10 years showed the lowest success rate and a significantly lower BMI-SDS reduction both at end of intervention and 1 year later compared to obese adolescents. These observations are in concordance with the study of Danielsson et al. showing no clinical relevant weight loss in extremely obese adolescents (11). In conclusion, lifestyle intervention is much more effective in extremely obese children than in extremely obese adolescents, while the success rate and BMI-SDS reduction were similar in obese children and obese adolescents. As in our study, the success rate was only 20% in extremely obese adolescents; this suggests that other interventions (for example drugs or bariatric surgery) beside lifestyle interventions are necessary in the majority of adolescents with severe obesity if we cannot improve the lifestyle intervention for this target group. The reasons for this difference concerning effectiveness of lifestyle intervention between extremely obese children and adolescents remain unclear. While in the last decade lifestyle interventions focused on children, it becomes quite clear in recent years that interventions involving parents are more effective than interventions solely for obese children (6,7,26,28–31). Maybe, the limited effect of parents on health behaviour habits of adolescents explains at least the disappointing findings in lifestyle intervention of extremely obese adolescents (32). In contrast, other studies report that even adolescents mimic the health behaviour of their parents (33). However, obese children did not differ significantly in respect to BMI-SDS reduction during lifestyle intervention from obese adolescents. This finding points against a simple age effect in lifestyle interventions. It can be speculated that the worse outcome in extremely obese adolescents is also caused by certain characteristics of these patients and their
Change of BMI-SDS during 1-year intervention
Change of BMI-SDS between baseline and 1 year after end of intervention (= 2 years after baseline)
−0.28 ± 0.35 −0.36 ± 0.36 −0.26 ± 0.35 −0.12 ± 0.30
−0.25 ± 0.46 −0.38 ± 0.41 −0.26 ± 0.23 −0.10 ± 0.48
families (e.g. lack of psychosocial support and parenting skills), by a decline in the motivation for lifestyle changes, or by inadvertent constraints to therapy adherence (34). Indeed, we found the highest dropout rate in extremely obese adolescents according to the literature reporting an increased dropout rate in extremely obese adolescents participating in a lifestyle intervention (10). In multiple linear regression analyses, baseline BMI-SDS was not significantly related to changes of BMI-SDS at end of intervention or at follow-up. This finding can be explained by summing children < 10 years and > 10 years in these analyses. Extremely obese children (≤10 years) responded better than obese children (≤10 years), while extremely obese adolescents (>10 years) responded poorer than obese adolescents (>10 years).
Strengths and limitations of the study The strengths of this study are the large study sample, the intention-to-treat approach, the multicentre design, the analysis of obese children naive to drugs and the follow-up period after end of treatment. However, some potential limitations of our study have to be considered. First, BMI percentiles were used to classify overweight. Although BMI is a good measure for overweight, one needs to be aware of its limitation as an indirect measure of fat mass. Furthermore, success was defined by change of BMI-SDS and not of change of fat mass. Using the BMI-SDS to describe weight changes has some limitations (35) probably also explaining in part why the extremely obese ≤10 years might reduce their degree of overweight greater than the obese children. Second, we are not able to differentiate the effect of diet and increased physical exercise on weight loss because of our study protocol. Furthermore, the effects of dieting and increased physical activity probably strengthened each other. Third, we cannot exclude different socio-economic backgrounds or lifestyle habits in the participants of the intervention programme. Fourth, the children were
© 2013 The Authors Pediatric Obesity © 2013 International Association for the Study of Obesity. Pediatric Obesity 10, 7–14
not randomized to different treatment centres and we have no untreated control group. However, for ethical reasons, it seems difficult to prevent obese children from a potential effective intervention. One might argue that the changes of BMI-SDS in our study might occur even without intervention. Indeed, population-based studies have reported a slight decrease in BMI-SDS in overweight not treatmentseeking children (36). In contrast, our participants were obese and extremely obese as well as treatment seeking. Without intervention, obese and extremely obese children and adolescents tend to increase their weight (37,38). Moreover, the prevalence of extremely obese children and adolescents is increasing in the United States pointing against spontaneous normalization of weight (4,39). Furthermore, we have previously reported the changes of BMI-SDS in treatment-seeking obese children and adolescents without the lifestyle intervention ‘Obeldicks’ (22,40): The control group of obese children in these studies demonstrated a slight increase of BMI-SDS. Fifth, we have to keep in mind that the changes of BMI-SDS represent in part the statistic phenomenon regression to the mean. As this effect is likely larger in the extremely obese compared with obese children and adolescents, this phenomenon seem not to explain the disappointing results in extremely obese adolescents. Finally, the high loss to follow-up rate which is typical for lifestyle interventions in obese children and adolescents is an important limitation. If the participants with lost to follow-up increased their BMI-SDS over the 2 years, the effect of our lifestyle intervention would be overestimated because of our statistical approach setting BMI-SDS back to baseline in participants with lost to follow-up. However, all of participants with loss to follow-up were categorized as treatment failures in the intention-to-treat approach. In summary, our study demonstrated an encouraging effect of lifestyle intervention in extremely obese children ≤10 years both at end of intervention and 1 year later, but only a limited effect in extremely obese adolescents >10 years. Therefore, other therapeutic approaches seem to be needed in severe obese adolescents if we are not able to improve lifestyle programmes for extremely obese adolescents.
Conflict of interest statement All authors have no conflicts of interest.
Acknowledgement We thank the participating children and adolescents.
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