General obesity or abdominal obesity - what should we be focussing upon in children? Dr. David McCarthy RNutr Institute for Health Research & Policy London Metropolitan University 13 th February 2008 Oxford Obesity Seminars

What is the time bomb? Type 2 diabetes Hypertension Metabolic Syndrome CVD Stroke

Diagnostic Criteria for Metabolic Syndrome in Children 3 or more of the following: –BMI >98 th centile –TG>95 th centile –HDL <5 th centile –SBP +/- DBP>95 th centile –Impaired GTT

National Child Measurement Programme One element of the Government’s work programme on childhood obesity Inform local planning and delivery of services for children; gather population-level surveillance data to allow analysis of trends in growth patterns and obesity. dsocialcaretopics/Healthyliving/DH_073787

UK 1990 BMI References Cole et al. Arch Dis Child (1995) 73: 25-29

Some drawbacks of BMI in children Age-dependent Correlates with both fat mass and fat-free mass Low sensitivity no indication of body fat distribution

‘Although body mass index is simple to measure and has been a valuable tool in monitoring trends in obesity, it also has numerous disadvantages. Principally it does not distinguish between increased mass in the form of fat, lean tissue or bone, and hence can lead to significant misclassification.’ McCarthy et al. 2006

‘The fact that body mass index represents only a crude proxy for body fat and may produce a significant level of misclassification is universally accepted but widely ignored. This is because, in the absence of alternative measures, the advantages of body mass index have outweighed its disadvantages.’ McCarthy et al. 2006

Correlation of BMI with Fat Mass (kg) r 2 = 0.763, P< year olds

Correlation of BMI with Fat Free Mass (kg) r 2 = 0.514, P< year olds

Misclassification by BMI Overweight/obese children can be classified as normal At least 6.5% overfat/obese children misclassified by BMI* *McCarthy et al. unpublished observations

Abdominal fat in adults Visceral fat, intra- abdominal fat Strongly linked to morbidity insulin resistance and hyperinsulinaemia Waist circumference – a measure of abdominal, intra-abdominal and visceral fat

Waist Measurement Now a common measure in adults Risk for diabetes, hypertension and CVD Cut-offs identified Where do you take the waist measurement?

Central body fat accumulation in children Intra-abdominal adipose tissue Subcutaneous abdominal adipose tissue assessed by girth and skinfold measurements

Intra-abdominal fat and morbidity in children Brambilla et al Caprio et al. 1995, 1996 Owens et al Adverse changes in blood lipids, insulin and blood pressure

Is waist circumference in children linked to risk? Adverse lipoprotein profile in year olds (Flodmark et al. 1994) Adverse insulin levels in 5-17 year olds Freedman et al. 1999) Raised systolic blood pressure in 4-5 year olds (Jarrett, McCarthy et al, 2002, unpublished)

WC percentile charts for children Cuban (Martinez et al. 1994) Italian (Zannolli & Morgese 1996) Spanish (Moreno et al. 1999) UK (McCarthy et al. 2001) Canadian (Katzmarzyk et al. 2004) US (Fernandez et al. 2004) Australian (Eisenmann et al. 2005)

n, 8355 McCarthy et al Development of WC centile charts for the UK children

Child Growth Foundation

BMI-WC relationship SubjectAgeBMI WC BMI %ile WC %ile (y) (cm) A ~50th <9th B ~50th >98th C >91st ~50th D >98th>99.6th

Has upper body fatness increased in British children? Comparison of data collected 10 and 20 years apart BSI and NDN surveys

McCarthy et al BMJ 326: 624 NDNS boys NDNS girls BSI boys BSI girls

McCarthy et al BMJ 326: 624 NDNS girls NDNS boys BSI girls BSI boys

Changes over years in mean BMI and waist circumference in British children aged years. Mean SD Score (SD)Mean increase over time (SE) BSI 1977/87NDNS 1997 MaleFemaleMaleFemaleMaleFemale BMI (1.02)(0.99)(1.13)(1.09)(0.06)(0.06) WC (0.99)(1.00)(1.02)(1.33)(0.06)(0.06) McCarthy et al BMJ 326: 624

Changes over years in overweight and obesity based on BMI and waist circumference in British children aged years. Values are % exceeding 91 st centile (98 th centile) % prevalence of overweight % change (obesity)over time BSI 1977/87NDNS 1997 MaleFemaleMaleFemaleMaleFemale BMI (3.3)(1.6)(10.0)(8.3)(6.8)(6.6) WC (3.3)(3.1)(13.8)(17.1)(10.7)(14.5) McCarthy et al BMJ 326: 624

Are these changes in WC also seen in younger children? The ALSPAC Study

Avon Longitudinal Study of Parents And Children ALSPAC comprises 14,000 children born in the Avon region during 1991 and 1992 (Golding et al. 2001). Children in Focus (CIF) is a subset of this cohort (approx children) For this study, BMI and WC from the CIF cohort were compared with equivalent BSI data between 2.5 and 5 years

BSI BMICIF BMI nAge (y) Mean (SD) (kgm 2 ) Median (kgm 2 ) nAge (y) Mean (SD) (kgm 2 ) Median (kgm 2 ) D (kgm 2 ) % D Boys (1.3) * (1.3) (1.4) * (1.2) (1.3) * (1.3) (1.2) (1.4) Girls (1.3) * (1.3) (1.4) * (1.5) (1.4) * (1.5) (1.6) * (1.6) McCarthy HD et al. (2005). Increasing waist circumferences in young British children - a comparative study. Int J Obesity 29: Results - BMI

BSI waist circumferenceCIF waist circumference nAge (y) Mean (SD) (cm) Median (cm) nAge (y) Mean (SD) (cm) Median (cm) D (cm) %D Boys (3.0) * (3.0) (3.1) * (3.0) (3.1) * (3.2) (3.2) * (3.5) Girls (2.8) * (3.1) (3.1) * (3.6) (3.6) * (3.6) (3.7) * (4.2) McCarthy HD et al. (2005). Increasing waist circumferences in young British children - a comparative study. Int J Obesity 29: Results – Waist Circumference

Increase in central fatness in British youths and pre-school children

Hackney

Hackney Demography Relatively young population 50% from black and minority ethnic groups High rates of social and economic deprivation CVD death rate twice national average High prevalence of type 2 diabetes

Hackney Children's Obesity Survey

Ethnicity-related variation in upper body fatness in East London schoolchildren. By DIMPLE SAMANI 1, LIZ PROSSER 2, COLIN ALSTON 2, and H. DAVID McCARTHY 1, 1 Institute for Health Research & Policy, London Metropolitan University, Holloway Rd, London N7 8DB, 2 The Learning Trust, 1 Reading Lane, London, E8 1GQ. Proceedings of the Nutrition Society (2007, in press)

CaucasianMixedS. AsianCaribbeanAfricanOther MFMFMFMFMFMF n Ht SDS WC SDS WHtR Hackney Children’s Obesity Survey Measures of central fatness across ethnic groups

CaucasianMixedS. AsianCaribbeanAfricanOther MFMFMFMFMFMF Overwt % WC Obese % WC Overwt % BMI Obese % BMI %> WHtR Prevalence of obesity across ethnic groups using different assessment criteria

Key Findings Within a socially homogenous group of children, variation in upper body fatness is evident Ethnic variation was striking Prevalence of upper body obesity based solely upon WC in South Asian was not as great as in other ethnic groups When height is accounted for, ethnicity-related variation is less obvious Caution should be exercised when interpreting WC measures between children from different ethnic groups

Problems with waist measurement No universally agreed definition of measurement site Measure over skin or clothing? Difficulty with very obese subjects Sensitivity issues

Waist circumference measurement Midway between the 10 th rib and the iliac crest WHO standard method Used by : McCarthy et al Freedman et al Moreno et al. 1999

Waist circumference measurement continued. At the level of the umbilicus Used for the waist circumference percentiles in Italian children, Zanolli & Morgese. 1996

Dimple Samani-Radia

Conclusions BMI can fail to identify all children at risk of obesity- related morbidity Abdominal fatness strongly linked to morbidity Waist girth measurement is a useful adjunct to BMI Upper body fatness has increased in young children and in youths Greater attention should be paid to central obesity in children

Acknowledgements Dimple Samani Karen Jarrett ALSPAC team Tanita UK NoCLoR The Learning Trust IHRP Tim Cole

Thank you

New children's body fat charts