McCarthy13Feb08

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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
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 >98th centile
TG>95th centile
HDL <5th centile
SBP +/- DBP>95th 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
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)
16-18 year olds
r2 = 0.763, P<0.0001
Correlation of BMI with Fat Free Mass (kg)
16-18 year olds
r2 = 0.514, P<0.0001
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 unpublished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, intraabdominal 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. 1994
• Caprio et al. 1995,
1996
• Owens et al. 1998
• Adverse changes in
blood lipids, insulin
and blood pressure
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)
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)
Development of WC centile charts for the UK children
n, 8355
McCarthy et al. 2001
Child Growth Foundation
BMI-WC relationship
Subject Age BMI
(y)
A
B
C
D
7.7
7.5
7.1
7.1
15.2
15.3
19.1
20.0
WC BMI %ile WC %ile
(cm)
48
65
53
67
~50th
~50th
>91st
>98th
<9th
>98th
~50th
>99.6th
Has upper body fatness
increased in British children?
Comparison of data collected
10 and 20 years apart
BSI and NDN surveys
**
82
Waist circumference (cm)
NDNS boys
78
**
**
**
74
**
**
**
**
NDNS girls
BSI boys
70
**
**
**
12
13
BSI girls
66
**
62
58
10
11
14
15
Age group (years)
McCarthy et al. 2003. BMJ 326: 624
16
17
NDNS girls
NDNS boys
BSI girls
BSI boys
McCarthy et al. 2003. BMJ 326: 624
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
Male Female
NDNS 1997
Male Female
Male
BMI
-0.05 -0.15
(1.02) (0.99)
0.42
0.38
(1.13) (1.09)
0.47
0.53
(0.06) (0.06)
WC
0.00
0.00
(0.99) (1.00)
0.84
1.02
(1.02) (1.33)
0.84
1.02
(0.06) (0.06)
McCarthy et al. 2003. BMJ 326: 624
Female
Changes over 10-20 years in overweight and obesity based
on BMI and waist circumference in British children aged 1116 years. Values are % exceeding 91st centile (98th centile)
% prevalence of overweight
(obesity)
% change
over time
BSI 1977/87
Male Female
NDNS 1997
Male Female
Male
Female
BMI
7.7
(3.3)
5.9
(1.6)
20.6
17.3
(10.0) (8.3)
12.9
(6.8)
11.4
(6.6)
WC
8.7
(3.3)
8.8
(3.1)
28.5
38.1
(13.8) (17.1)
19.8
29.3
(10.7) (14.5)
McCarthy et al. 2003. 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. 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
BSI BMI
n
CIF BMI
Age
(y)
Mean (SD)
(kgm2)
Median
(kgm2)
n
182
2.5
16.4 (1.3)
16.3
528
205
3.5
16.3 (1.4)
16.1
195
4.5
16.0 (1.3)
251
5.5
186
Age
(y)
Mean (SD)
(kgm2)
Median
(kgm2)
D
(kgm2)
%D
2.5
16.7* (1.3)
16.6
0.29
1.8
580
3.5
16.5* (1.2)
16.4
0.22
1.4
15.8
563
4
16.2* (1.3)
16.1
0.26
1.6
15.9 (1.2)
15.7
534
5
16.0 (1.4)
15.9
0.09
0.6
2.5
16.3 (1.3)
16.1
429
2.5
16.5* (1.3)
16.4
0.27
1.7
185
3.5
16.0 (1.4)
15.9
467
3.5
16.5* (1.5)
16.3
0.42
2.6
210
4.5
16.0 (1.4)
15.9
454
4
16.2* (1.5)
16.1
0.26
1.6
406
5.5
15.5 (1.6)
15.2
445
5
16.1* (1.6)
15.9
0.63
4.1
Boys
Girls
McCarthy HD et al. (2005). Increasing waist circumferences in young British children
- a comparative study. Int J Obesity 29: 157-162.
Results – Waist Circumference
BSI waist circumference
n
Age
(y)
Mean (SD)
(cm)
Median
(cm)
182
2.5
48.4 (3.0)
206
3.5
195
251
CIF waist circumference
n
Age
(y)
Mean (SD)
(cm)
Median
(cm)
D
(cm)
%D
48.3
536
2.5
50.4* (3.0)
50.3
1.99
4.1
50.9+ (3.1)
50.4
575
3.5
51.7* (3.0)
51.7
0.76
1.5
4.5
51.9+ (3.1)
51.6
559
4.0
52.5* (3.2)
52.4
0.60
1.2
5.5
52.3+ (3.2)
52.5
531
5.0
53.1* (3.5)
52.8
0.86
1.6
186
2.5
47.8 (2.8)
47.6
433
2.5
50.2* (3.1)
50.2
2.50
5.2
185
3.5
49.8 (3.1)
49.7
467
3.5
51.7* (3.6)
51.6
1.88
3.8
210
4.5
51.0 (3.6)
50.6
454
4
52.3* (3.6)
52.0
1.34
2.6
406
5.5
51.3 (3.7)
51.2
444
5
52.9* (4.2)
52.3
1.53
2.9
Boys
Girls
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
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 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)
Hackney Children’s Obesity Survey
Measures of central fatness across ethnic groups
Caucasian
n
Mixed
S. Asian
Caribbean
African
Other
M
F
M
F
M
F
M
F
M
F
M
F
437
394
125
113
224
215
199
176
286
291
102
105
0.12
Ht
SDS
0.26
-0.05
0.50
0.50
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
Mixed
S. Asian
Caribbean
African
Other
M
F
M
F
M
F
M
F
M
F
M
F
Overwt
%
WC
27.2
25.8
24.0
20.4
17.9
19.5
23.6
33.0
29.7
38.6
28.4
28.6
Obese
%
WC
14.4
13.5
9.6
8.8
8.5
8.4
12.1
18.8
12.9
21.6
11.8
9.5
Overwt
%
BMI
21.7
19.5
17.6
18.7
14.1
15.7
23.0
27.0
27.0
28.0
11.5
15.9
Obese
%
BMI
10.4
9.9
5.6
6.9
5.8
6.0
13.5
16.5
13.3
17.8
6.8
6.5
%>
WHtR
0.50
17.6
17.0
12.7
8.7
10.0
11.2
12.1
16.5
11.5
17.9
13.7
15.2
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 10th 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
Conclusions
• 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
Acknowledgements
•
•
•
•
•
•
•
•
Dimple Samani
Karen Jarrett
ALSPAC team
Tanita UK
NoCLoR
The Learning Trust
IHRP
Tim Cole
Thank you
New children's body fat charts
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