Waist-to-height ratio as a measure of abdominal obesity in southern Chinese and European children and adolescents.

BACKGROUND: Waist-to-height ratio (WHtR), with a 0.5 threshold (WHtR0.5), is regarded as a simple age- and gender-independent criterion of abdominal obesity (AO) and a better predictor than the 90th percentile of waist circumference (WCP90). OBJECTIVE: An analysis of gender and ethnic differences of WHtR and other AO indices between children and adolescents from southern China (HK: Hong-Kong, China) and Europe (LD: Lódz, Poland). SUBJECTS: Two large cross-sectional surveys of children and adolescents aged 7-19 years, one from LD (13 172) and one from HK (14 566). METHODS: The percentile and standardized values of WHtR and other parameters (WC, body mass index (BMI)) were assessed using the LMS method. The WHtR values corresponding to WCP90 and to the BMI definition of global obesity (BMIP95) were evaluated with the polynomial regression model. The compliance of the AO prevalence data, obtained with two criteria (WCP90 vs WHtR0.5) was analyzed using Cohen's kappa index (κC). RESULTS: The WHtR data of Polish subjects were generally higher than those of their HK peers, and the ethic differences increased with age. The WHtR values of HK boys showed a stronger relationship with BMI z-score. WHtR corresponding to WCP90 assumed values <0.5. An application of Cohen's kappa coefficient (κC) to Polish subjects showed either 'substantial' (κC>0.6) or 'almost perfect' (κC>0.8) agreement in the AO prevalence for both criteria (WCP90 and WHtR0.5). For these criteria, either 'fair' (κC <0.4) or 'moderate' (κC<0.6) AO consistency ratings were observed among HK girls. In HK boys, a significant difference in the prevalence of AO was observed, independent of the criterion used. CONCLUSIONS: Our results provide further evidence of the need for developing ethnic-specific WC charts and for recommending that a WHtR cutoff of 0.5 may not be appropriate to predict cardiometabolic risk in children of different ethnic groups.

Regular exercise and a healthy dietary pattern are associated with lower resting blood pressure in non-obese adolescents: a population-based study.

The study aims to assess the association of diet and frequency of extracurricular physical activity (PA) on blood pressure (BP) in non-obese adolescents. A total of 7185 non-obese adolescents aged 12-18 years were analysed to elucidate the relationship between BP and exercise/eating habit. Totally, 10.3% of the boys and 4.6% of the girls who responded to the questionnaire reported undertaking regular extracurricular physical exercise > or =3 times/week and were classified as being physically active. An unhealthy eating habit (UEH) score was constructed by counting the number of 'yes' responses to 11 dietary behavioural items considered to be unhealthy. In logistic regression analysis, age, body mass index, exercise frequency and UEH were significantly associated with BP (P<0.001). The odds ratios (ORs) for high BP in physically more active adolescents vs those who were less active was 0.48 (95% confidence interval (CI) 0.30-0.77). The OR for high BP in those with UEH scores in the highest quartile vs those with UEH scores in the lowest quartile was 1.63 (95% CI 1.24-2.15). In conclusion, regular exercise and a healthy diet are positively associated with lower BP even in non-obese adolescents.

Self-reported waist circumference: a screening tool for classifying children with overweight/obesity and cardiometabolic risk factor clustering.

OBJECTIVES: The objectives of this study were twofold - (i) to assess the agreement between self-reported waist circumference (SRWC) and assessor measured waist circumference (MWC) and (ii) to evaluate the diagnostic ability of SRWC for classifying (i) a clustering of cardiometabolic risk factors (CMRFs) and (ii) overweight/obese status in Hong Kong Chinese children aged 6-18 years. METHODS: A cross-sectional study with cluster random sampling was conducted. A self-administrated questionnaire, which included demographic data, body weight, body height and waist circumference, was given to children to bring home for completion. Children were asked to return the questionnaire and fast themselves for at least 8 h on the day of the survey. Anthropometric measurements and blood pressure were taken by trained research staff and fasting blood samples were collected for measurements of fasting plasma glucose, total cholesterol, triglyceride, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol. RESULTS: A total of 515 boys and 711 girls were included in the data analysis. Agreement between SRWC and MWC was assessed by intra-class correlation coefficient and it ranged from 0.77 to 0.87. The ability of sex-specific SRWC values to classify children with a clustering of CMRFs and overweight/obesity exhibited moderately high to high sensitivity and specificity, and the area under the receiver operating characteristics ranged from acceptable to excellent (from 0.76 to 0.84). CONCLUSIONS: SRWC has good agreement with MWC and could be used as a screening tool to classify children with a clustering of CMRFs and overweight/obesity status in Hong Kong Chinese children.

Implications of using World Health Organization growth reference (2007) for identifying growth problems in Hong Kong children aged 6 to 18 years.

OBJECTIVE: To evaluate the implications of replacing Hong Kong's 1993 growth references (HK1993) with the World Health Organization's 2007 references (WHO2007) for children aged 6 to 18 years. DESIGN: Cross-sectional study. SETTING: Thirty-six randomly selected primary and secondary schools in Hong Kong. PARTICIPANTS: A total of 14 842 children and adolescents aged 6 to 18 years in Hong Kong during 2005/06. MAIN OUTCOME MEASURES: Creation of age-specific z-scores for height, weight, and body mass index relative to HK1993 and WHO2007 references. RESULTS: Use of WHO2007 instead of HK1993 could classify an additional 1.4% children aged 6 to 10 years and 2.8% children aged 11 to 18 years as having a short stature. Using WHO2007, respective proportions that could be classified as underweight and obese increased by 3.5% and 2.1% among children aged 6 to 10 years, and 5.5% and 1.6% among children aged 11 to 18 years. CONCLUSIONS: Use of WHO2007 could increase clinical workload and patient and parent anxiety by 'over-diagnosing' short stature and underweight. Although WHO2007 may have a role in international comparative research, retention of HK1993 would seem appropriate from a clinical perspective.

Breakfast frequency inversely associated with BMI and body fatness in Hong Kong Chinese children aged 9-18 years.

The present study assessed the relationship between breakfast frequency and measures of obesity in Hong Kong Chinese children aged 9-18 years. A total of 11,570 children (50 % boys) underwent anthropometric measurements and completed a simple self-administered dietary behaviour questionnaire. Their parents completed a questionnaire providing demographic information. Breakfast frequency was assessed by a single question, 'How many days over the past week did you have breakfast?' Children were categorised into three groups: skippers (ate breakfast 0-2 times/week); semi-skippers (ate breakfast 3-4 times/week); non-skippers (ate breakfast 5-7 times/week), to assess all associated characteristics. Of the 3644 primary and 7926 secondary school students, 8 % (8·7 % of boys and 6·9 % of girls) and 14 % (14 % of boys and 15 % of girls), respectively, were breakfast skippers. The prevalence of obesity among breakfast skippers, semi-skippers and non-skippers was, respectively, 9·8, 10·6 and 3·8 % (P < 0·001) for primary school students and 3·9, 3·1 and 2·4 % (P < 0·001) for secondary school students. The 12 % of Hong Kong children aged 9-18 years who skipped breakfast had higher BMI, BMI z-scores and percentage of body fat (PBF) than their counterparts. The dose effects of breakfast frequency (unstandardised regression coefficient, P < 0·001) on BMI and PBF were, respectively, -0·125 kg/m2 and -0·219 % for boys and -0·165 kg/m2 and -0·353 % for girls, adjusting for physical activity per additional breakfast meal per week. Further study is recommended to elucidate whether regular breakfast consumption may have a role in the prevention of childhood obesity.

Factors associated with length of hospital stay in children with respiratory disease.

OBJECTIVES: To explore factors associated with length of stay, and secondarily to explore the potential of enhanced diagnostics to address respiratory disease burden in children. DESIGN: Prospective study. SETTING: A university teaching hospital in Hong Kong. PATIENTS: Data from 475 children with respiratory tract symptoms or fever admitted to Prince of Wales Hospital, Hong Kong from November 2005 to April 2007. MAIN OUTCOME MEASURES: Aetiological diagnoses based on enhanced diagnostics and their association with clinical information. RESULTS: Data from 469 subjects showed that major presentations were fever (84%), cough (72%), and runny nose (64%). The median length of stay was longest (3 days) for adenovirus, metapneumovirus and mycoplasma infections, while children with negative aetiological results had a median length of stay of 2 days. Fever duration during admission (P<0.001), the highest recorded temperature during admission (P < 0.001), use of antibiotics during admission (P<0.001), ear pain before admission (P = 0.019), and high white cell counts (P = 0.021) were associated with increased length of stay (univariate analysis). Identifying an aetiological agent did not affect length of stay. Comparison of children with a positive immunofluorescence test result (rapidly available) with those in whom the test was negative though a positive multiplex polymerase chain reaction ensued (result not available to clinicians) also showed no association with length of stay. CONCLUSION: Although rapid enhanced diagnostics may not have a major influence on length of stay, these data form an integral part of enhanced sentinel surveillance systems.

Higher exercise frequency associated with lower blood pressure in Hong Kong adolescents: a population-based study.

The aim of this study was to determine the association between blood pressure and the frequency of structured physical training activity in Chinese adolescents. A total of 9558 students aged 11-18 years underwent anthropometric and blood pressure measurements in a cross-sectional growth study. Structured physical training activity was assessed by two simple self-administered questions and parents were asked to complete a questionnaire providing demographic information. Ninety per cent of eligible students participated in the study, of which 94% provided data on physical training frequency for final analysis. Of the boys, 22.6% and of the girls, 14.5% were physically active with extracurricular school exercise at least twice a week. Over half of the students did not regularly exercise except during physical education classes at school. Blood pressure had a positive correlation with body mass index (BMI). Both systolic blood pressure and diastolic blood pressure were substantially decreased with increased training frequency (P<0.05). Logistic regression adjusting for age, family history of hypertension, BMI and sleep duration showed that exercising two or more times a week had a negative relation with hypertension (odds ratio: 0.63, 95%CI 0.47-0.85). In conclusion, structured physical training activity of two or more times a week has a beneficial effect on blood pressure in Hong Kong children aged 11-18 years.

Identification of viral and atypical bacterial pathogens in children hospitalized with acute respiratory infections in Hong Kong by multiplex PCR assays.

Acute respiratory tract infection is a leading cause of hospital admission of children. This study used a broad capture, rapid and sensitive method (multiplex PCR assay) to detect 20 different respiratory pathogens including influenza A subtypes H1, H3, and H5; influenza B; parainfluenza types 1, 2, 3, and 4; respiratory syncytial virus (RSV) groups A and B; adenoviruses; human rhinoviruses; enteroviruses; human metapneumoviruses; human coronaviruses OC43, 229E, and SARS-CoV; Chlamydophila pneumoniae; Legionella pneumophila; and Mycoplasma pneumoniae; from respiratory specimens of 475 children hospitalized over a 12-month period for acute respiratory tract infections. The overall positive rate (47%) was about twice higher than previous reports based on conventional methods. Influenza A, parainfluenza and RSV accounted for 51%, and non-cultivable viruses accounted for 30% of positive cases. Influenza A peaked at March and June. Influenza B was detected in January, February, and April. Parainfluenza was prevalent throughout the year except from April to June. Most RSV infections were found between February and September. Adenovirus had multiple peaks, whereas rhinovirus and coronavirus OC43 were detected mainly in winter and early spring. RSV infection was associated with bronchiolitis, and parainfluenza was associated with croup; otherwise the clinical manifestations were largely nonspecific. In general, children infected with influenza A, adenovirus and mixed viruses had higher temperatures. In view of the increasing concern about unexpected outbreaks of severe viral infections, a rapid multiplex PCR assay is a valuable tool to enhance the management of hospitalized patients, and for the surveillance for viral infections circulating in the community.

Ambulatory blood pressure in children with obstructive sleep apnoea: a community based study.

BACKGROUND: Childhood obstructive sleep apnoea (OSA) is increasingly being recognised. Its effects on blood pressure (BP) elevation and hypertension are still controversial. OBJECTIVE: To evaluate the association between OSA and ambulatory BP in children. METHODS: Children aged 6-13 years from randomly selected schools were invited to undergo overnight sleep study and ambulatory BP monitoring after completing a validated OSA questionnaire. OSA was diagnosed if the obstructive apnoea-hypopnoea index (AHI) was >1, and normal controls had AHI <1 and snoring <3 nights per week. Children with OSA were subdivided into a mild group (AHI 1-5) and moderate to severe group (AHI >5). RESULTS: 306 subjects had valid sleep and daytime BP data. Children with OSA had significantly higher BP than normal healthy children during both sleep and wakefulness. BP levels increased with the severity of OSA, and children with moderate to severe disease (AHI >5) were at significantly higher risk for nocturnal systolic (OR 3.9 (95% CI 1.4 to 10.5)) and diastolic (OR 3.3 (95% CI 1.4 to 8.1)) hypertension. Multiple linear regression revealed a significant association between oxygen desaturation index and AHI with daytime and nocturnal BP, respectively, independent of obesity. CONCLUSIONS: OSA was associated with elevated daytime and nocturnal BP, and is an independent predictor of nocturnal hypertension. This has important clinical implications as childhood elevated BP predicts future cardiovascular risks. Future studies should examine the effect of therapy for OSA on changes in BP.

The effect of diet and strength training on obese children's physical self-concept.

AIM: The aim of this study was to examine the effects of a 6-week diet and exercise program, with emphasis on strength training, on the physical self-concept, body composition, and physical fitness of young overweight and obese children. METHODS: Eighty-two overweight and obese children aged 8-11 years were randomized into a diet-only or a diet-and-strength training group. Self-concept, body composition and physical fitness were measured before and after the 6-week study period using the Physical Self Description Questionnaires (PSDQ), dual-energy X-ray absorptiometry (DXA), and standard fitness tests. Dietary intake was assessed with a food frequency questionnaire. Total daily energy intake was significantly reduced in both groups with a trend of more reduction in the diet-only group. RESULTS: Both groups developed greater confidence in strength. Those in the diet-and-strength training group also improved their endurance self-concept. Body Mass Index (BMI) decreased significantly in both groups. Lean mass increased significantly in both groups but significantly more in the diet-and-strength training group (+0.8 kg vs +0.3 kg, P<0.05). Handgrip, shuttle run, sit-up, and push-up were significantly improved in both groups, to a significantly greater extent in the diet-and-strength training group. CONCLUSION: These findings confirm the 6-week program of either diet-only or diet-and-strength training improved overweight/obese children's self-perception of muscular strength and body composition. With the diet-and-strength training program, self-concept in endurance also improved and the gain in lean body mass was more than double that of the diet only group.

Childhood obesity, gender, actual-ideal body image discrepancies, and physical self-concept in Hong Kong children: cultural differences in the value of moderation.

Childhood obesity is increasingly prevalent in Western and non-Western societies. The authors related multiple dimensions of physical self-concept to body composition for 763 Chinese children aged 8 to 15 and compared the results with Western research. Compared with Western research, gender differences favoring boys were generally much smaller for physical self-concept and body image. Objective and subjective indexes of body fat were negatively related to many components of physical self-concept, but--in contrast to Western research--were unrelated to global self-esteem and slightly positively related to health self-concept. In support of discrepancy theory, actual-ideal discrepancies in body image were related to physical self-concept. However, consistent with the Chinese cultural value of moderation, and in contrast to Western results, being too thin relative to personal ideals was almost as detrimental as being too fat. The results reflect stronger Chinese cultural values of moderation and acceptance of obesity than in Western culture and have implications for social and educational policy in China.

Waist circumference and body mass index in Chinese children: cutoff values for predicting cardiovascular risk factors.

BACKGROUND: Body mass index (BMI) and waist circumference (WC) correlate with cardiovascular (CV) risk factors in childhood which track into adulthood. WC provides a measure of central obesity, which has been specifically associated with CV risk factors. Reference standards for WC, and for WC and BMI risk threshold values are not established in Chinese children. OBJECTIVES: To construct reference percentile charts of WC, establish relationships between WC, BMI and other risk factors, and propose WC and BMI threshold values predictive of CV risk factors in Hong Kong ethnic Chinese children. METHODS: Weight, height, waist and hip circumference were measured in 2593 (52% boys, 47% girls) randomly sampled Hong Kong school children aged 6-12 years. In 958 of these and 97 additional overweight children (n=1055), the relationships between WC, BMI, waist/hip and waist/height ratio and six age-adjusted CV risk factors (>85% percentile levels of blood pressure (BP), fasting triglycerides, low-density lipoprotein (LDL) cholesterol, glucose and insulin levels, and <15% percentile levels of high-density lipoprotein (HDL) cholesterol) were studied. Receiver-operating characteristic analysis was employed to derive optimal age-adjusted sex-specific WC and BMI thresholds for predicting these measures of risk. RESULTS: WC percentiles were constructed. WC correlated slightly more than BMI with CV risk factors and most strongly with insulin and systolic BP, but poorly or not with LDL and glucose. Optimal WC and BMI risk thresholds for predicting four of these six CV risk factors were ca. the 85th percentiles (sensitivities approximately 0.8, specificities approximately 0.87) with age-specific cutoff values in girls/boys from approximately 57/58 to approximately 71/76 cm and 17/18 to 22/23 kg/m(2). CONCLUSION: These are the first set of WC reference data for Chinese children. WC risk cutoff values are proposed which, despite a smaller waist in Chinese children, are similar to those reported for American children. WC percentiles may reflect population risk.

Cough frequency in children with mild asthma correlates with sputum neutrophil count.

BACKGROUND: A study was undertaken to measure cough frequency in children with stable asthma using a validated monitoring device, and to assess the correlation between cough frequency and the degree and type of airway inflammation. METHODS: Thirty six children of median age 11.5 years (interquartile range (IQR) 9-14) with stable asthma were recruited. They underwent spirometric testing, exhaled nitric oxide (eNO) measurement, sputum induction for differential cell count, and ambulatory cough monitoring for 24 hours. Coughing episodes were counted both as individual spikes and as clusters. RESULTS: All children had mild intermittent asthma and their median forced expiratory volume in 1 second and eNO were 83.3% (IQR 81.1-97.6) and 56.1 ppb (IQR 37.4-105), respectively. The median number of cough episodes per day was 25.5 (IQR 16-42.8). Sputum induction was successful in 69% of the subjects and cough frequency was found to have a significant positive correlation with sputum neutrophil count (r = 0.833, p = 0.0001). CONCLUSIONS: Children with stable mild asthma have increased cough frequency that might be driven by a neutrophilic inflammatory pathway.

Longer term follow up of aerobic capacity in children affected by severe acute respiratory syndrome (SARS).

BACKGROUND: A study was undertaken to investigate the aerobic capacity and pulmonary function of children 6 and 15 months after the diagnosis of severe acute respiratory syndrome (SARS). METHODS: Thirty four patients of mean age 14.7 years completed both pulmonary function and maximal aerobic capacity tests at 6 months. All had normal clinical examination and were asymptomatic. Their exercise responses were compared with a group of healthy controls. Complete data were collected on 27 of the original 34 cases at 15 months. RESULTS: Compared with normal controls, the patient group had significantly lower absolute and mass related peak oxygen consumption (peak V o(2) (p<0.01)), higher ventilatory equivalent for oxygen (p<0.01), lower oxygen pulse (p<0.01), and a lower oxygen uptake efficiency slope (p<0.01) at 6 months. This impairment was unexpected and out of proportion with the degree of lung function abnormality. Residual high resolution computed tomography of thorax (HRCT) abnormalities were present in 14 patients. Those with abnormal HRCT findings had significantly lower mass related peak V o(2) than subjects with normal radiology (p<0.01). Absolute and mass related peak V o(2) in the patient group remained impaired at 15 months despite normalisation of lung function in all patients. CONCLUSIONS: The mechanism for the reduced aerobic capacity in children following SARS is not fully understood, but it is probably a consequence of impaired perfusion to the lungs at peak exercise and deconditioning.

In vitro anti-allergic activities of a newly concocted traditional Chinese medicine--the wheeze-relief formula.

Asthma is one of the most common chronic diseases worldwide. Western medications such as glucocorticoids are effective therapeutic agents but may be associated with side effects. Traditional Chinese medicine (TCM) has been used for treating allergic diseases with observable clinical benefits. The present study investigated whether a novel TCM concoction, the wheeze-relief formula (WRF), possesses in vitro anti-allergic activities. We measured the effects of WRF on the release of eosinophil cationic protein (ECP) by human eosinophils using fluorescence enzyme immunoassay, expression of chemokine receptor CCR3 and adhesion molecule CD49d on eosinophils using immunophenotyping, cytokine induction from peripheral blood mononuclear cells (PBMC) using cytometric bead array (CBA), and the gene expression of cytokines and cytokine receptors using cDNA expression array. Results demonstrated that WRF dose-dependently and significantly: (1) suppressed ECP release from eosinophils activated with granulocyte macrophage-colony stimulating factor (GM-CSF) and platelet activating factor (PAF); (2) inhibited the expression of CCR3 and CD49d on PAF-activated eosinophils; and (3) attenuated the production of tumor necrosis factor alpha and gene expression of IL-2 receptor chain alpha (CD25) on house dust mite (Der p 1) activated PBMC. The above results suggest a possible anti-allergic role of WRF and provide a biochemical basis for further clinical trial on human subjects.

Kawasaki disease in Hong Kong, 1994 to 2000.

OBJECTIVE: To describe the epidemiology, clinical characteristics, and management of Kawasaki disease in children in Hong Kong. DESIGN: Retrospective survey of medical records from July 1994 to June 1997, and prospective data collection from July 1997 to June 2000. SETTING: Hospitals with a paediatric unit in Hong Kong. PATIENTS: Patients diagnosed with Kawasaki disease between July 1994 and June 2000 in public hospitals in Hong Kong. MAIN OUTCOME MEASURES: Incidence of Kawasaki disease and coronary artery aneurysm rates. RESULTS: A total of 696 cases of Kawasaki disease were reported. There were 435 (62.5%) boys and 261 (37.5%) girls giving a male to female ratio of 1.7:1. The age ranged from 1 month to 15 years 5 months with a median of 1.7 years. Infants (<1 year) constituted the largest group of patients (223, 32.0%) and overall, 638 (91.7%) were younger than 5 years. Skin rash, conjunctivitis, and oral signs were among the principal clinical features present in over 80% of cases. Prominent cervical lymph nodes larger than 1.5 cm were less commonly found (24%). Coronary artery aneurysms or ectasia were present in 15.7% (109/696), 8.5% (59/696), and 5.0% (35/696) of patients at 2, 4, and 8 weeks, respectively. The incidence of Kawasaki disease per 100,000 children under 5 years was significantly higher in the prospective study period than in the retrospective period (39 vs 26, P<0.001). CONCLUSION: The incidence of Kawasaki disease is high in Hong Kong and is 39 per 100,000 children below 5 years of age. The coronary artery aneurysm prevalence is 5%. Intravenous gamma-globulin and high-dose aspirin is the mainstay of treatment.

Induced sputum in childhood asthma.

Asthma is characterised by variable degrees of airway obstruction, airway hyper-responsiveness, and chronic airway inflammation. Current guidelines emphasise that inhaled corticosteroid treatment is the mainstay of asthma therapy because it targets the underlying airway inflammation. It is prudent to use the lowest possible dose of inhaled corticosteroid compatible with good asthma control. In clinical practice, the use of or the reduction of inhaled corticosteroid dosage is based on symptoms and lung function, both of which have been shown to have a poor correlation with airway inflammation. The use of induced sputum as a marker of airway inflammation improves asthma monitoring and optimises treatment in adults. This review discusses the technique of sputum induction, its clinical application, and our experience of its use in asthmatic children.

Self-perception of physical competences in preadolescent overweight Chinese children.

OBJECTIVE: To compare self-perceptions of physical competences in overweight and in normal weight preadolescent Chinese children. DESIGN: Cross-sectional study. SETTING: Three primary schools and a university hospital in Hong Kong. SUBJECTS: A total of 634 children, comprising 558 (462 normal weight, 96 overweight) aged 8-12 y randomly sampled from three primary schools, and 76 similar age overweight children recruited from the community for a diet and exercise intervention programme. MEASUREMENTS: Height, weight and percentage body fat were measured. Self-perceptions of physical competences were determined by Physical Self-Descriptive Questionnaire (PSDQ). Corresponding actual physical competences were measured by physical fitness tests. RESULTS: Overweight children perceived themselves to have significantly more body fat than normal weight children, with poorer appearance, sports competence, endurance, coordination, flexibility, overall physical self-concept and self-esteem, but to be no less healthy, no less physically active and no less strong. Overweight children performed less well than normal weight children in measures of endurance, coordination and flexibility but better in strength. Poor self-perception of physical competences appeared only partly related to deficiencies in actual physical competences. CONCLUSION: Overweight children have poorer self-perception of their physical competences but do not perceive themselves to be less strong, healthy or physically active than normal weight children. Exercise programmes for overweight children could be more effective if designed with the knowledge of these self-perceptions.