4363.0.55.001 - National Health Survey: Users' Guide - Electronic Publication, 2007-08  
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This document was added or updated on 17/09/2009.


BODY MASS INDEX (BMI) CUT-OFF POINTS

BMI cut-off points for adolescents and children

The following table shows the cut-off points for the grouping of BMI scores for underweight, overweight and obesity, by sex, for exact years and half-years between two and 18 years. (Underweight has three categories of thinness: thinness grades 1, 2, and 3, corresponding to severe, moderate and mild thinness).

Cut-off points for each grouping for children are based on corresponding cut-off points for persons aged 18 years and over; i.e: a score of 22.77 for a nine year old boy is equivalent to a score of 30 (obese) for an adult, and a score of 13.59 for a ten-and-a-half year old girl is equivalent to a score of 17 (moderate thinness) for an adult.

The cut-off points for underweight (equivalent to BMI scores of 16, 17 and 18.5 in adults) are sourced from Cole et al, Body mass index cut offs to define thinness in children and adolescents: international survey, 2007. The cut-off points for overweight (equivalent to a BMI score of 25 for an adult) and obesity (equivalent to a BMI score of 30 for an adult) are the cut-off points for children and adolescents sourced from Cole et al, Establishing a standard definition for child overweight and obesity worldwide: international survey, 2000.

In this table, ranges for underweight show the top of the range (up to 12.58, up to 16.98, etc), while ranges for overweight and obese show the bottom of the range (from 17.15, from 19.30, etc).

Children with BMI scores that fit between the top range for underweight and the bottom range for overweight are classified as being in the normal weight range.

Height and weight data for children in the NHS was only collected for children aged five years and over. As age is only available for whole years in the NHS, BMI calculations for children are based on the half-year cut-off points, as these are considered to provide an essentially unbiased estimate of prevalence. For example, a child who is recorded in the survey as being seven years old may have just turned seven, or may be shortly turning eight, so the half-year cut-off provides a mid-point across all seven year olds in the survey. This methodology assumes a fairly even spread of ages in years and months for each age group.

Standard BMI output categories for the NHS are underweight, normal weight, overweight and obese, or combinations of these. Other output is available on request.

Body Mass Index (BMI) cut-off points for children and adolescents
Underweight
Overweight
Obese
Age (in years)
Adult cutoff point 16.00
Adult cutoff point 17.00
Adult cutoff point 18.50
Adult cutoff point 25.00
Adult cutoff point 30.00
Boys
5
12.66
13.31
14.21
17.42
19.30
5.5
12.58
13.22
14.13
17.45
19.47
6
12.50
13.15
14.07
17.55
19.78
6.5
12.45
13.10
14.04
17.71
20.23
7
12.42
13.08
14.04
17.92
20.63
7.5
12.41
13.09
14.08
18.16
21.09
8
12.42
13.11
14.15
18.44
21.60
8.5
12.45
13.17
14.24
18.76
22.17
9
12.50
13.24
14.35
19.10
22.77
9.5
12.57
13.34
14.49
19.46
23.39
10
12.66
13.45
14.64
19.84
24.00
10.5
12.77
13.58
14.80
20.20
24.57
11
12.89
13.72
14.97
20.55
25.10
11.5
13.03
13.87
15.16
20.89
25.58
12
13.18
14.05
15.35
21.22
26.02
12.5
13.37
14.25
15.58
21.56
26.43
13
13.59
14.48
15.84
21.91
26.84
13.5
13.83
14.74
16.12
22.27
27.25
14
14.09
15.01
16.41
22.62
27.63
14.5
14.35
15.28
16.69
22.96
27.98
15
14.60
15.55
16.98
23.29
28.30
15.5
14.86
15.82
17.26
23.60
28.60
16
15.12
16.08
17.54
23.90
28.88
16.5
15.36
16.34
17.80
24.19
29.14
17
15.60
16.58
18.05
24.46
29.41
17.5
15.81
16.80
18.28
24.73
29.70
18
16.00
17.00
18.50
25.00
30.00
Girls
5
12.50
13.09
13.94
17.15
19.17
5.5
12.40
12.99
13.86
17.20
19.34
6
12.32
12.93
13.82
17.34
19.65
6.5
12.28
12.90
13.82
17.53
20.08
7
12.26
12.91
13.86
17.75
20.51
7.5
12.27
12.95
13.93
18.03
21.01
8
12.31
13.00
14.02
18.35
21.57
8.5
12.37
13.08
14.14
18.69
22.18
9
12.44
13.18
14.28
19.07
22.81
9.5
12.53
13.29
14.43
19.45
23.46
10
12.64
13.43
14.61
19.86
24.11
10.5
12.78
13.59
14.81
20.29
24.77
11
12.95
13.79
15.05
20.74
25.42
11.5
13.15
14.01
15.32
21.20
26.05
12
13.39
14.28
15.62
21.68
26.67
12.5
13.65
14.56
15.93
22.14
27.24
13
13.92
14.85
16.26
22.58
27.76
13.5
14.20
15.14
16.57
22.98
28.20
14
14.48
15.43
16.88
23.34
28.57
14.5
14.75
15.72
17.18
23.66
28.87
15
15.01
15.98
17.45
23.94
29.11
15.5
15.25
16.22
17.69
24.17
29.29
16
15.46
16.44
17.91
24.37
29.43
16.5
15.63
16.62
18.09
24.54
29.56
17
15.78
16.77
18.25
24.70
29.69
17.5
15.90
16.89
18.38
24.85
29.84
18
16.00
17.00
18.50
25.00
30.00