General obesity or abdominal obesity - what should we be focussing upon in children?

1. 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 13th February 2008 Oxford Obesity Seminars

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

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

5. 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. • http://www.dh.gov.uk/en/Policyandguidance/Healthandsocialcaretopics/Healthyliving/DH_073787

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

7. 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

9. ‘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

10. ‘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

11. Correlation of BMI with Fat Mass (kg) 16-18 year olds r2= 0.763, P<0.0001

12. Correlation of BMI with Fat Free Mass (kg) 16-18 year olds r2 = 0.514, P<0.0001

13. 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 unpublished observations

14. 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

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

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

20. Intra-abdominal fat and morbidity in children • Brambilla et al. 1994 • Caprio et al. 1995, 1996 • Owens et al. 1998 • Adverse changes in blood lipids, insulin and blood pressure

21. Is waist circumference in children linked to risk? Adverse lipoprotein profile in 12-14 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)

22. 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)

24. Development of WC centile charts for the UK children n, 8355 McCarthy et al. 2001

25. Child Growth Foundation

26. BMI-WC relationship Subject Age BMI WC BMI %ile WC %ile (y) (cm) A 7.7 15.2 48 ~50th <9th B 7.5 15.3 65 ~50th >98th C 7.1 19.1 53 >91st ~50th D 7.1 20.0 67 >98th >99.6th

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

29. NDNS boys NDNS girls BSI boys BSI girls McCarthy et al. 2003. BMJ326: 624

30. NDNS girls NDNS boys BSI girls BSI boys McCarthy et al. 2003. BMJ326: 624

31. Changes over 10-20 years in mean BMI and waist circumference in British children aged 11-16 years. • Mean SD Score (SD) Mean increase • over time (SE) • BSI 1977/87 NDNS 1997 • Male Female Male Female Male Female • BMI -0.05 -0.15 0.42 0.38 0.47 0.53 • (1.02) (0.99) (1.13) (1.09) (0.06) (0.06) • WC 0.00 0.00 0.84 1.02 0.84 1.02 • (0.99) (1.00) (1.02) (1.33) (0.06) (0.06) • McCarthy et al. 2003. BMJ326: 624

32. Changes over 10-20 years in overweight and obesity based on BMI and waist circumference in British children aged 11-16 years. Values are % exceeding 91st centile (98th centile) % prevalence of overweight % change (obesity) over time BSI 1977/87 NDNS 1997 Male Female Male Female Male Female BMI 7.7 5.9 20.6 17.3 12.9 11.4 (3.3) (1.6) (10.0) (8.3) (6.8) (6.6) WC 8.7 8.8 28.5 38.1 19.8 29.3 (3.3) (3.1) (13.8) (17.1) (10.7) (14.5) McCarthy et al. 2003. BMJ326: 624

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

35. 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. 1000 children) • For this study, BMI and WC from the CIF cohort were compared with equivalent BSI data between 2.5 and 5 years

36. Results - BMI McCarthy HD et al. (2005). Increasing waist circumferences in young British children - a comparative study. Int J Obesity 29: 157-162.

37. Results – Waist Circumference McCarthy HD et al. (2005). Increasing waist circumferences in young British children - a comparative study. Int J Obesity 29: 157-162.

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

39. Hackney

40. 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

41. Hackney Children's Obesity Survey

42. Ethnicity-related variation in upper body fatness in East London schoolchildren. By DIMPLE SAMANI1, LIZ PROSSER2, COLIN ALSTON2, and H. DAVID McCARTHY1, 1Institute for Health Research & Policy, London Metropolitan University, Holloway Rd, London N7 8DB, 2The Learning Trust, 1 Reading Lane, London, E8 1GQ. Proceedings of the Nutrition Society (2007, in press)

43. Hackney Children’s Obesity Survey Measures of central fatness across ethnic groups

44. Prevalence of obesity across ethnic groups using different assessment criteria

45. 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

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

48. Waist circumference measurement Midway between the 10th rib and the iliac crest WHO standard method Used by : McCarthy et al. 2001 Freedman et al. 1999 Moreno et al. 1999

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

50. Dimple Samani-Radia