Dr. David McCarthy RNutr
Institute for Health Research & Policy
London Metropolitan University
13 th February 2008
Oxford Obesity Seminars

• Type 2 diabetes
• Hypertension
• Metabolic Syndrome
• CVD
• Stroke

• 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.
• http://www.dh.gov.uk/en/Policyandguidance/Healthan dsocialcaretopics/Healthyliving/DH_073787

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)
16-18 year olds r 2 = 0.763, P <0.0001

Correlation of BMI with Fat Free Mass (kg)
16-18 year olds r 2 = 0.514, P <0.0001

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observations unpublished

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

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

• Intra-abdominal adipose tissue
• Subcutaneous abdominal adipose tissue
• assessed by girth and skinfold measurements

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

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)

• 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)

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

Child Growth Foundation

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

Comparison of data collected
10 and 20 years apart
BSI and NDN surveys

82
78
74
70
**
**
**
**
**
**
**
**
**
66
62
**
58
10 11 12 13 14 15
Age group (years)
McCarthy et al. 2003. BMJ 326: 624
**
NDNS boys
**
NDNS girls
BSI boys
BSI girls
16 17

McCarthy et al. 2003. BMJ 326: 624
NDNS girls
NDNS boys
BSI girls
BSI boys

Changes over 10-20 years in mean BMI and waist circumference in British children aged 11-16 years.
Mean SD Score (SD)
BMI
WC
BSI 1977/87
Male Female
-0.05
-0.15
(1.02) (0.99)
0.00
0.00
(0.99) (1.00)
NDNS 1997
Male Female
0.42
0.38
(1.13) (1.09)
0.84
1.02
(1.02) (1.33)
Mean increase over time (SE)
Male Female
0.47
0.53
(0.06) (0.06)
0.84
1.02
(0.06) (0.06)
McCarthy et al. 2003. BMJ 326: 624

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 91 st centile (98 th centile)
BMI
WC
% prevalence of overweight
(obesity)
BSI 1977/87
Male Female
NDNS 1997
Male Female
7.7
5.9
(3.3) (1.6)
8.7
8.8
(3.3) (3.1)
20.6
17.3
(10.0) (8.3)
28.5
38.1
(13.8) (17.1)
% change over time
Male Female
12.9
11.4
(6.8) (6.6)
19.8
29.3
(10.7) (14.5)
McCarthy et al. 2003. BMJ 326: 624

?
The ALSPAC
Study

A
L
S
P
A
C
• 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

Results - BMI n Age
(y)
BSI BMI
Mean (SD)
(kgm 2 )
Median
(kgm 2 ) n
Boys
182 2.5
16.4 (1.3) 16.3
205 3.5
16.3 (1.4) 16.1
195 4.5
16.0 (1.3) 15.8
251 5.5
15.9 (1.2) 15.7
Girls
186 2.5
16.3 (1.3) 16.1
185 3.5
16.0 (1.4) 15.9
210 4.5
16.0 (1.4) 15.9
406 5.5
15.5 (1.6) 15.2
528 2.5
580 3.5
563 4
534 5
429 2.5
467 3.5
454 4
445 5
Age
(y)
CIF BMI
Mean (SD)
(kgm 2 )
Median
(kgm 2 )
D
(kgm 2 )
% D
16.7* (1.3) 16.6
16.5* (1.2) 16.4
16.2* (1.3) 16.1
16.0 (1.4) 15.9
16.5* (1.3) 16.4
16.5* (1.5) 16.3
16.2* (1.5) 16.1
16.1* (1.6) 15.9
0.29
0.22
0.26
0.09
0.27
0.42
0.26
0.63
1.7
2.6
1.6
4.1
1.8
1.4
1.6
0.6
McCarthy HD et al. (2005). Increasing waist circumferences in young British children
- a comparative study. Int J Obesity 29: 157-162.

Results – Waist Circumference n
Boys
182
206
195
251
Girls
186
185
210
406
BSI waist circumference
Age
(y)
Mean (SD)
(cm)
Median
(cm)
2.5
3.5
4.5
5.5
2.5
3.5
4.5
5.5
48.4 (3.0)
50.9
+ (3.1)
51.9
+ (3.1)
52.3
+ (3.2)
47.8 (2.8)
49.8 (3.1)
51.0 (3.6)
51.3 (3.7)
48.3
50.4
51.6
52.5
47.6
49.7
50.6
51.2
536
575
559
531
433
467
454
444
CIF waist circumference n Age
(y)
Mean (SD)
(cm)
Median
(cm)
D
(cm)
%D
2.5
3.5
4
5
2.5
3.5
4.0
5.0
50.4* (3.0)
51.7* (3.0)
52.5* (3.2)
53.1* (3.5)
50.2* (3.1)
51.7* (3.6)
52.3* (3.6)
52.9* (4.2)
50.3
51.7
52.4
52.8
50.2
51.6
52.0
52.3
1.99
4.1
0.76
1.5
0.60
1.2
0.86
1.6
2.50
5.2
1.88
3.8
1.34
2.6
1.53
2.9
McCarthy HD et al. (2005). Increasing waist circumferences in young British children
- a comparative study. Int J Obesity 29: 157-162.

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

Hackney

• 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 )

Hackney Children’s Obesity Survey
Measures of central fatness across ethnic groups
Caucasian
M F
Mixed
M F
S. Asian Caribbean
M F M F
African
M F M
Other
F n
Ht
SDS
437
0.12
394 125
0.26
113 224 215
-0.05
199
0.50
176 286
0.50
291 102 105
0.12
WC
SDS
0.68
0.81
0.51
0.32
0.02
0.12
0.57
0.81
0.65
0.98
0.58
0.52
WHtR 0.45
0.45
0.45
0.44
0.44
0.44
0.44
0.45
0.45
0.45
0.45
0.45

Prevalence of obesity across ethnic groups using different assessment criteria
Caucasian
M F M
Mixed
F
S. Asian
M F
Caribbean
M F
African
M F M
Other
F
Overwt
%
WC
Obese
%
WC
Overwt
%
BMI
Obese
%
BMI
%>
WHtR
0.50
27.2
25.8
24.0
20.4
17.9
19.5
23.6
33.0
29.7
38.6
28.4
28.6
14.4
13.5
10.4
9.9
9.6
21.7
19.5
17.6
18.7
14.1
15.7
23.0
27.0
27.0
28.0
11.5
15.9
5.6
8.8
6.9
8.5
5.8
8.4
6.0
12.1
13.5
18.8
16.5
12.9
13.3
21.6
17.8
11.8
6.8
9.5
6.5
17.6
17.0
12.7
8.7
10.0
11.2
12.1
16.5
11.5
17.9
13.7
15.2

• 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

• 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. 2001
Freedman et al. 1999
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

• BMI can fail to identify all children at risk of obesityrelated 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

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