Is it relevant, when discussing individual determinants of obesity, to consider the
common assumption that specific psychological and/or risk factor profiles are
causally related to obesity? The reverse question must also be asked: what is the evidence
that psychological and socioeconomic characteristics are not the consequences,
but rather the causes, of the obese state?
There has been a strong interest in studying the relation between socioeconomic status (SES) and obesity. Previous studies have shown that the association between
SES and obesity may vary by population, sex and age . H owever, a p erson’s body
weight status may also affect his/her education and occupational opportunities,
which subsequently affect his/her SES. A good understanding of the association
between obesity and SES has many important public health and policy implications,
particularly for the prevention and management of obesity. It is well known that obesity
is more prevalent in the lower socioeconomic classes and that this pattern is more
common among women than men. Even so, there is a varying relation of SES with
obesity between countries at different stages of development .
A landmark review of studies published prior to 1989 on SES and obesity proposed
that obesity in the developing world would be essentially a disease of the socioeconomic
elite . However, in a recent review from developing countries, the authors concluded from the studies they had
reviewed that obesity in the developing world is no longer a disease of groups with
higher SES. Additionally, the burden of obesity in each developing country tends to
shift towards the groups with lower SES as the country’s gross national product
increases. They also concluded that the shift of obesity in women with low SES apparently
occurs at an earlier stage of economic development than it does for men.
Socioeconomic gradients with respect to obesity, even in the Western world, are both
heterogeneous and in transition. For example, it has long been accepted that in the US
population, groups with low SES are at greater risk to be obese than people of high SES.
This perception, however, was challenged in a recent study . Based on nationally
representative data collected in the National Health and Nutrition Examination Surveys
from American adults since the 1970s, the findings indicated an overall trend of a weakening
association between SES and obesity, with differing patterns across ethnic groups.
In a study of children and young people grouped by race, sex, and age, different results
were observed in the association between overweight and SES. Between 1988–1994 and
1999–2002, the ratio in the prevalence of overweight in adolescent boys with a low or
high SES decreased from 2.5 to 1.1 and from 3.1 to 1.6 in girls (fig. 1) . Consistently
across almost all SES groups, the prevalence of overweight was much higher in blacks
than in whites, indicating highly complex patterns in the association of SES and overweight
. The authors speculated that television viewing might have been the primary
type of inactivity in poor adolescents during the early part of the period they were
studying, whereas computers and computer games became more widely accessible and
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affordable during the more recent part of the observation period, especially in high SES
groups. Accordingly, the energy intake and expenditure patterns of all adolescents
regardless of SES, particularly for white adolescent boys, became more similar, resulting
in smaller economic disparities of the proportion of overweight subjects. Similarly, data
from the US show that in the 70s there was as much as a 50% relative difference in obesity
prevalence among those with less than high school education, compared to people
with college education, but by 1999–2000, the difference had decreased to 14% .
Similar observations of a decreasing socioeconomic gradient in obesity were reported
in one Swedish study of young adults . These findings underline that individual
characteristics are probably not the main cause of the current obesity epidemic. In addition,
changing patterns of consumption and of physical activity directly affect socioeconomic
differences in a way that is not always predictable.
The other side of the obesity-SES association is whether obesity can be shown to be a
risk factor for subsequent changes in SES. Among the first studies indicating that obesity
might affect social mobility was based on a Swedish population-based sample of
women examined in the late 1960s showing that the shift toward higher socioeconomic
level since childhood was more common in normal-weight than in overweight women
. However, this study did not establish which subjects were already overweight
as children. One US study, which classified adolescents and young adults as being
overweight or normal at baseline, found that the overweight group, 7 years later, were
less often married, had lower income and had completed fewer years of education.
These prospective findings were independent of initial SES, suggesting that obesity created
a situation of downward social mobility, and, in addition, more often occurring in
women than in men. Thus, in addition to the physical health consequences of obesity,
obese people, particularly obese women, suffer from social stigmatization, prejudice,
and discrimination . In a Swedish longitudinal study, no social difference in overweight
was observed at age 16 years but at 30 years educational level was associated with
overweight, reflecting the cumulative influence of multiple adverse circumstances experienced
from adolescence to young adulthood .
Potential mechanisms for an effect of obesity on subsequent social status have
been proposed, the most obvious being related to the stigmatisation experienced by
the obese. Leanness is often equated with beauty, success, fitness and self-control.
Obesity, on the other hand, is considered as undesirable as leanness is desirable, for
reasons that are more often related to cosmetic concerns than to actual or potential
medical complications. Specific examples for discrimination may be seen in the areas
of marital, employment and educational opportunities. If obesity has both social
causes and effects, a self-perpetuating cycle may be created that reinforces the relationship
between low SES and obesity.
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