The Psychology of Eating: From Healthy to Disordered Behavior

Obesity 149

population is being considered – someone could be obese in India but not
in the US. It is therefore not used for adults but is still used for children
as it enables the child’s height and weight to be examined separately.

Body Mass Index

Obesity is also defined in terms of Body Mass Index (BMI), which is cal-
culated using the equation weight (kg) / height (m2). This produces a figure
which is categorized as normal weight (18.5–24.9), overweight (grade 1:
25–29.9), clinical obesity (grade 2: 30 –39.9), or severe obesity (grade 3: 40).
This is the most frequently used definition of obesity. These gradings are
illustrated in figure 8.1. BMI, however, does not allow for differences in
weight between muscle and fat – a bodybuilder would be defined as obese.
Further, it is particularly limited at detecting obesity in people with BMIs
in the intermediate ranges, and it has been suggested that the problems
with BMI might account for some of the conflicting evidence around the
association between obesity and mortality (Romero-Corral et al.,2008;
Rothman, 2008; and see below).

Waist circumference

BMI is the most frequently used measure of obesity but it does not allow
for an analysis of the location of fat. This is important since some problems
such as diabetes are predicted by abdominal fat rather than lower body fat.
Researchers originally used waist–hip ratios to assess obesity, but recently
waist circumference on its own has become the preferred approach. Weight
reduction is recommended when waist circumference is greater than 102 cm
in men and greater than 88 cm in women (Lean, Han, and Morrison, 1995;
Lean, Han, and Seidall, 1998). A reduction in waist circumference is associated
with a reduction in cardiovascular risk factors, and abdominal obesity is
associated with insulin resistance and the development of Type 2 diabetes
(Chan et al., 1994; Han et al., 1997). Waist circumference has been suggested
as the basis for routine screening in primary care (Despres, Lemieux, and
Prud’homme, 2001), although Little and Byrne (2001) have argued that
more evidence is needed before such a program should be implemented.

Percentage body fat

As health is mostly associated with fat rather than weight per se,
researchers and clinicians have also developed methods of measuring