A Health Disparities Perspective on Obesity Research (ref:ncbi)
Abstract
Obesity
is a major risk factor for chronic disease and can decrease longevity,
quality of life, and economic productivity. Compelling ethical, human
rights, and practical reasons exist for addressing social disparities in
obesity, which requires systematically applying a disparities
perspective to obesity research and relevant policy. A disparities
perspective guides us to consider multiple dimensions and levels of
social advantage and disadvantage and how those advantages and
disadvantages produce disparities in obesity and its consequences.
Introduction
Obesity is a major risk factor for chronic disease and can decrease longevity, quality of life, and economic productivity (1),
and research should examine how obesity and its consequences are
patterned socially. A health disparities perspective, which
systematically examines how health is distributed across racial/ethnic
and socioeconomic groups, can contribute to obesity research.
The
most elegant definition of health disparities was offered by Margaret
Whitehead: "Differences which are unnecessary and avoidable but, in
addition, are also considered unfair and unjust" (2).
The following definition is more complex and less elegant but addresses
some conceptual and measurement challenges: a health disparity is a
particular type of difference in health (or in the determinants of
health that could be shaped by policies) in which disadvantaged social
groups systematically experience worse health or more health risks than
do more advantaged social groups. Disadvantaged social groups include
racial/ethnic minorities, low-income people, women, or others who have
persistently experienced discrimination (3).
Health disparities put socially disadvantaged groups at further
disadvantage regarding their health because poor health then elevates
their risk of further social disadvantage (eg, through health-related
job loss), which then can exacerbate their ill health, and so on (3). This compounding of disadvantage is what makes health disparities particularly unfair.
Applying a Disparities Lens to Research on Obesity
To
apply a disparities lens to any health research endeavor is to
systematically seek to identify and understand disparities in health
among more and less advantaged social groups. This approach contrasts
with prevailing approaches to health research in the United States,
which often examine racial or ethnic groups without 1) explaining why
they are examined, 2) considering social class, or 3) examining
race-related social factors such as racial segregation, which could
strongly affect a person's health (4).
If social class is considered, prevailing approaches often measure it
inadequately and control for it rather than study its effects. A
disparities lens highlights health or health-related differences closely
linked with differences in social advantage on both socioeconomic and
racial/ethnic lines. In the case of obesity research, modifiable
conditions in people's lives can be examined to discover how — in homes,
neighborhoods, schools, and workplaces — they affect the likelihood of
attaining and maintaining healthy weight.
The stepwise
incremental socioeconomic differences observed in many health outcomes,
whereby health gradually improves as socioeconomic factors improve (5),
are not as clear-cut for obesity. For example, obesity among women
followed a marked socioeconomic gradient during the 1970s, but more
recently the socioeconomic disparities in obesity have actually narrowed
because of a larger increase in obesity among higher than among lower
socioeconomic status groups (6). Among children, obesity appears to be related to family income but does show a clear stepwise pattern (Figure 1).
The poorest have the highest and the richest the lowest obesity rates;
the middle groups, however, appear similar to one other. Adult obesity
prevalence has a similar pattern.
To
complicate matters, patterns of obesity — and of socioeconomic
disparities in obesity — vary markedly by race or ethnic group, by sex,
and over time (8).
This complexity presents an opportunity to obtain clues about
potentially remediable causes. Patterns that shift across social groups
over time suggest that modifiable factors are probably involved.
Ethical and human rights reasons
Ethical
principles dictate that all people should be valued equally and have
equal opportunities to be healthy. Health is essential for well-being
and economic self-sufficiency; thus, resources needed for health should
be distributed equitably, which many have interpreted to mean according
to need. It is difficult, however, to define and measure need (3,9,10).
Human
rights principles can provide assistance. According to well-established
human rights norms and agreements signed by almost all nations, the
right to health is the right to attain the highest level of health
possible (11-13). This concept has been criticized for being difficult to operationalize for measurement purposes (14).
However, the health of the most privileged social groups (eg, the
dominant racial/ethnic group or the wealthiest group) indicates what
should be possible for everyone (3,15).
Human rights norms, principles, and agreements oblige governments to
make good faith efforts toward progressively removing obstacles to all
people's realizing their full health potential, particularly for those
social groups that historically have experienced more obstacles.
Practical reasons
Differences in a range of health indicators according to diverse measures of social class have been observed for centuries (16) and across virtually all societies in which they have been studied (17). Health has been reported by race in the United States for more than a century (18,19), although the issue of racial/ethnic disparities in health became prominent only during the past 2 decades (20,21).
Many health researchers routinely report results by racial/ethnic group
but do not examine health differences by markers of social class, such
as income or education. Inadequate socioeconomic information often has
reinforced a widespread tendency to make unfounded assumptions about the
nature of racial or ethnic disparities in health, reifying genetic or
"cultural" explanations and deflecting attention from potentially
remediable social factors (22).
A
disparities lens can focus on neglected factors in health research,
increasing the likelihood of sound conclusions, not only about social
disparities in health but also about a range of research questions,
including ones assumed to be purely biomedical. Failure to adequately
consider social factors can result in erroneous conclusions from
research findings, even on many questions that are not in themselves
focused on social issues but for which social factors may play a role as
confounders, mediators, or effect-modifiers (23).
Neglected Dimensions to Consider in Applying a Disparities Lens
The
human rights concept of removing obstacles to realizing rights,
including the right to health, particularly among those who historically
have experienced more obstacles, can enrich obesity research. It can
push us to focus on the root causes of social advantage and disadvantage
implicated in obesity disparities. This approach contrasts with the
prevailing approach, which generally focuses on the behaviors that
immediately lead to obesity without considering the factors that shape
the behaviors.
Examination of social disadvantage and
advantage is crucial to social disparities research. It is challenging,
however, because of the limited amount of information on them in most
health studies. Social advantage or disadvantage can be material,
psychosocial, or both.
Material and psychosocial dimensions of social advantage and disadvantage
Social
disadvantage can be based on material conditions, determined by access
to resources and services that affect health such as adequate nutrition,
sanitation, housing, and medical care. It also can be of a psychosocial
nature, based on human relationships and their psychological effects.
For example, unfair treatment based on one's race or ethnic group can
cause psychological distress. In addition, one's awareness of being in a
group that has historically suffered discrimination could act as a
chronic stressor, even in the absence of overt incidents of unfair
treatment. These dimensions often coexist and interact. Material
disadvantage (eg, resulting from inadequate income or wealth) can affect
obesity by influencing the ability to purchase nutritious food or to
live in a neighborhood with safe, pleasant places to exercise and
markets that sell affordable fresh produce. Material hardship also could
increase obesity risk insofar as it is a source of chronic stress;
stress could limit people's ability to change weight-related behaviors
even when informed and motivated (24-26).
Low educational attainment could increase the risk of obesity by
limiting economic opportunities or one's ability to understand and act
on health information.
Racial or ethnic group is
closely associated with social advantage and disadvantage and with
health disparities. Although each broad racial or ethnic group is
heterogeneous, overall, blacks, Hispanics, and American Indians have the
lowest and Asian Americans the highest incomes and educational levels;
whites have intermediate levels (27-29).
Racial or ethnic differences thus often reflect socioeconomic
differences, which can affect health through material pathways (23).
Experiences
of racism could include not only overt incidents of intentional
discrimination but also experiences in which unintended harm results
because of deeply rooted structural arrangements, such as those
perpetuating racial residential segregation. Racial segregation
systematically deprives blacks and Hispanics of opportunities to live in
health-promoting neighborhoods, in part by constraining their economic
opportunities (5,30).
These experiences could deleteriously affect health outcomes both
through material pathways and through psychosocial pathways involving
stress and physiologic responses to stress related to awareness of
unfair treatment or stigmatization (as a member of a socially excluded
group). Recent advances in understanding the neurophysiology of stress
and its effects on chronic disease have greatly increased our ability to
understand how both material and psychosocial disadvantage can harm
health (31).
Any
condition associated with stigma or lower social acceptance — such as
obesity — could lead to social disadvantage and accompanying adverse
health effects that are not intrinsic to that condition. Adverse health
effects could occur through material or psychosocial pathways. Examples
include physical or mental disability, HIV infection, or other highly
stigmatized diseases. Similarly, nonheterosexual orientation can result
in discrimination or social exclusion, putting one's health at risk in
multiple ways. These experiences of discrimination are rarely measured
in health studies.
Time dimension
Time
is another dimension of social advantage and disadvantage that can be
crucial to understanding health disparities. It seems likely that not
only the depth but also the duration of exposure to disadvantage could
matter greatly for health. Exposures that are potentially obesigenic,
such as a high-calorie diet, a crime-infested neighborhood without safe
places to exercise or play, or a resource-strapped school that offers
children few opportunities for supervised exercise, will likely have a
larger effect given a longer duration. Yet even when these factors are
measured at all, time is rarely considered. Current or last year's
income may be measured but generally not whether a person was poor as a
child. This oversight tends to underestimate racial/ethnic disparities
in social advantage. Our research with population-based data on
postpartum women in California confirms that at each level of current
income or education, non-Hispanic black and Hispanic women are more
likely than their non-Hispanic white counterparts to have grown up in
households of lower socioeconomic status (as reflected by their parents'
educational attainment) (23).
A
disparities perspective leads us to ask about not only the antecedents
of disparities in obesity but also the differential consequences of
obesity for people in different social groups. Finn Diderichsen of the
Karolinska Institute in Stockholm has developed a schematic diagram
highlighting the dynamic nature of how health disparities are produced
and reproduced over time. Figure 2,
adapted from Diderichsen, depicts how social position or stratification
(the extent to which different groups are sorted into hierarchies of
wealth, influence, and opportunities) leads to different
health-promoting or health-damaging exposures for different social
groups. Differences in social position influence not only whether a
person is exposed to a given health risk but also differential
vulnerability to disease incidence and severity and subsequent social
consequences of illness. For example, a highly educated person who,
because of obesity, develops heart disease with activity limitations may
be less likely than a manual worker with little schooling to become
unemployed. The highly educated person is more likely than the manual
worker to have work that is knowledge-based, less affected by physical
capacity, and more easily performed at home or on a more flexible
schedule.
How
health disparities are produced and reproduced across a lifetime and
generations, and possible points to intervene. Adapted from Finn
Diderichsen, Karolinska Institute, Stockholm; reprinted with permission.
Diderichsen's
diagram calls attention to multiple levels at which pathways toward
health disparity can be interrupted by policies, from the most proximal
level (proximal or downstream in relation to the outcome; eg, medical
treatment ameliorating the health damage done by harmful exposures
without addressing the exposures themselves) to the most distal level
(policies in the social context that may blunt the degree of social
stratification, such as policies supporting universal high-quality
education beginning in early childhood, and poverty reduction).
Levels of analysis to consider
Prevailing
research approaches tend to examine 1 level of aggregation or analysis —
usually the individual or household level. An accumulating body of
evidence indicates, however, that characteristics of the places where we
live, work, and learn may have health effects beyond the effects of
factors at the individual level. For example, the health effects of
being poor in a neighborhood with a high concentration of poor
households could be different from the consequences of being poor in a
neighborhood with a high concentration of richer households. These
effects may not be simple or predictable. Being poor in a poor
neighborhood may carry a higher risk of obesity, for example, if the
poor neighborhood lacks accessible, affordable sources of fresh foods,
safe places to exercise, or social norms that value healthy eating and
exercise .
Some multilevel research also has suggested that being poor in a more
affluent neighborhood may have adverse psychological effects if one
feels inferior to one's neighbors .
Similarly, for a person of a racial/ethnic minority, if living in a
neighborhood with a high concentration of people of the same
racial/ethnic minority meant living under conditions that make healthy
eating and exercise more difficult, obesity risks could be elevated.
Being the lone person of a racial/ethnic minority in a neighborhood
could, however, have negative psychological effects (eg, feelings of
isolation, exclusion, or less sense of belonging, or experiencing overt
bias), which could outweigh the positive effects of being in a place
with better resources and services .
Conclusions
A
disparities lens has much to contribute to health research in general
and to obesity research in particular. Focusing on disparities can guide
us to examine multiple dimensions and levels of advantage or
disadvantage, relative and absolute deprivation, discrimination, and
social exclusion. This perspective leads us to consider conditions in
both social and physical environments at the individual/household/family
and the community levels that can create opportunities and resources or
obstacles to health. Our attention is drawn to exposure to advantage
and disadvantage over time and to determinants of vulnerability to
exposure effects. We are reminded of an array of sources of advantage
and disadvantage, including cumulative stress related to material
poverty and the psychosocial stressors that often accompany it. Such a
research framework encourages us to consider social factors that seem
distal to obesity but could be highly relevant to experiences and
behaviors that result in biological processes underlying obesity and its
adverse clinical and social sequellae. A disparities perspective
encourages us not to rely entirely on simple categorizations of social
advantage or disadvantage, such as low income or educational level, but
to examine the actual distributions of the relevant factors and how they
relate to the health indicator of interest. Appropriate cut-points may
vary across indicators; Figure 1
shows that simple dichotomies (low income vs all others) do not fit the
data. A disparities perspective leads us to examine both race and
social class, together and separately, as points of departure.
A
disparities perspective leads us to ask the questions: What causes,
exacerbates, or ameliorates racial or ethnic or socioeconomic
differences in obesity during a person's lifetime and across
generations? Where and how can the pathways to obesity disparities be
interrupted most effectively and efficiently? Do interventions that
decrease obesity prevalence at the population level also reduce obesity
disparities across social groups, and vice versa? What are the
differential consequences of obesity, in health and social terms, for
people in different social groups? To answer these questions we must
study social factors rather than attempt to control for them.
High-quality disparities research looks for the root causes of social
disparities in health to inform efforts to intervene. In contrast,
prevailing approaches often take poverty, near-poverty, and
institutionalized racial bias as givens and focus primarily on how to
buffer the health-damaging effects. A disparities lens can make
practical contributions to obesity research, even regarding questions
whose central focus is not disparities.
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