joint strategic needs assessment foundation profile - JSNA

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13.4 Definitions and Classifications
13.4.1 Definition of Overweight and Obesity
13.4.1.1 Adults
Height and weight were collected as part of the local Health and Lifestyle Surveys.
However, it is well known that self-reported height tends to be overestimated and selfreported
weight tends to be underestimated compared to measured height and weight.
A survey of 4,808 British men and women aged 35-76 which compared self-reported
and measured height and weight (Spencer, Appleby et al. 2002), found that height was
overestimated by on average 1.23cm for men and 0.60cm for women, but the extent of
the overestimation was greater in older men and women, shorter men and heavier
women. They also found that weight was underestimated by on average 1.85kg for men
and 1.40kg for women and the extent of the underestimation was greater in heavier men
and women, but did not vary with age or height (although other studies in the other parts
of the world have found that the elderly particularly underestimate their weight
(Jalkanen, Tuomilehto et al. 1987; Kuczmarski, Kuczmarski et al. 2001)). These
differences were added or subtracted to the self-reported height and weight to try to
obtain a more realistic estimate of actual height and weight. For more details, including
the effects on the prevalence, are available in the Obesity and Exercise report resulting
from the Health and Lifestyle Survey 2007 at www.hullpublichealth.org.
Definitions of underweight, desirable or healthy weight, overweight and obesity are
defined on the basis of the body mass index (BMI) which is a measure of the weight to
height ratio. It was calculated by taking the adjusted weight (in kilograms) and dividing it
by the square of adjusted height (in metres). In adults, the cut-off values for BMI vary
for defining underweight and desirable weight, with some defining underweight as
having a BMI of less than 18.5 whereas others define underweight as having a BMI of
less than 20. For the purposes of the analysis below the local data uses underweight
defined as having a BMI of less than 20. In practice, differences in the definitions of
underweight are not of particular concern within this report as the focus is on presenting
information on overweight and obesity. Desirable weight is defined as having a BMI
more than (18.5 or) 20 but less than 25, overweight as having a BMI of 25 or more but
less than 30, and obesity is defined as having a BMI of 30 or more. Within this latter
category, morbidly obese is defined as having a BMI of 40 or more.
13.4.1.2 Children
There is little consensus on the “best” definition of childhood obesity in terms of BMI
owing to the marked changes of BMI profile in populations of children across time and
countries as well as over age. However, BMI remains the measure of choice in
assessing obesity in children. Approximations to the definitions of overweight and
obese children used by the Department of Health to produce Local Delivery Plan (LDP)
target figures for the childhood obesity indicator (Public Service Agreement: PSA10a)
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