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Primary Care

Prevalence and trends in overweight and obesity in three cross sectional studies of British children, 1974-94

BMJ 2001; 322 doi: https://doi.org/10.1136/bmj.322.7277.24 (Published 06 January 2001) Cite this as: BMJ 2001;322:24

Rapid Response:

Are obese children also overweight?

EDITOR-The paper by Chinn and Rona provides good
and bad news in equal measure.

The good news is their use of the new International
Obesity Task Force cut-offs for child BMI [1]. So their
rates of overweight and obesity, and the corresponding
changes over time, can be related directly to rates in
other studies around the world that use the same
cut-offs. The paper should encourage wider use of the
IOTF cut-offs.

The bad news of course is the evidence the paper
provides of a child obesity problem that has been
growing since 1984. The stature of the National Study
of Health and Growth makes its evidence hard to
ignore, and the paper provides a wake-up call for public
health measures to be targeted to address the
problem.

Unfortunately the IOTF definition of child overweight is
ambiguous, due to a lack of clarity in the original paper
[1]. It can be defined in either of two ways: (i) BMI
exceeding the overweight cut-off, or (ii) BMI lying
between the overweight and obesity cut-offs. By the first
definition obese children are also overweight, while by
the second they are not. The same problem arises with
cut-offs based on BMI centiles [2] - is an obese child,
above the 95th centile, also overweight or not?

I can confirm that the IOTF paper [1] intended the first
definition to be used. Chinn and Rona probably used it
too, though this needs to be clarified. But this usage
differs from that in adults, where overweight is BMI
between 25 and 30 kg/m2 and obesity is BMI exceeding
30 kg/m2. Either way there is the potential for confusion
that should be guarded against.

1. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH.
Establishing a standard definition for child overweight
and obesity: international survey. BMJ
2000;320:1240-3.

2. Must A, Dallal GE, Dietz WH. Reference data for
obesity: 85th and 95th percentiles of body mass index
(wt/ht2) and triceps skinfold thickness. Amer J Clin Nutr
1991;53:839-46.

Competing interests: No competing interests

12 January 2001
T J Cole
professor of medical statistics
Institute of Child Health