Epidemiology of Obesity
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Epidemiology of Obesity

March 8, 2020


Hello, my name is
Diana Grigsby-Toussaint and I am an Associate Professor at the University of Illinois
at Urbana-Champaign and today I’m really thrilled
to be able to talk to you about obesity epidemiology,
an area of my research. So, what do I hope you’ll get
out of this lecture at the end? So hopefully you can
answer the question well, what is epidemiology? And then more importantly
how do we use, how do we apply the principles
of epidemiology, uh, to the study of obesity? So what is epidemiology? So it’s the study
of the distribution and determinism
of disease frequency in health related events
in populations. That’s the first part
of the definition. And then the second part
is how do we apply that study to control health problems? So let’s break down
this definition a little bit further. So first we talked about
disease distribution, so what we want to know
is what do we understand about the patterns of disease
by person, place and time? Who are the people that
are getting the disease? Are we, do we tend to find
this particular condition in elderly people, or maybe
in, uh, younger individuals? Do we tend to find
a particular condition, um, in an area that is more urban
or more rural, for example, and what patterns
do we see over time? Do we find that the disease
is increasing over time, or is it de-or is it,
uh, decreasing over time, and what might
be those factors? So in the speaking of factors
we also talk about disease determinism when
it comes to epidemiology. What are the factors that
might bring about a-a change in a person’s health? So when we think about
obesity, for example, this might be that
if you were to exercise, individuals who exercise more
might be more likely, uh, less likely, for example,
to be overweight or obese because they’re b-burning
more calories. Or individuals that have diets
that are more energy dense are more likely to be,
uh, overweight, um, and we find those
individuals, then, would be at higher
risk for obesity. So what are these factors
that play some role with respect to why
people might have obesity? Disease frequency. So, as an epidemiologist
we also want to quantify well, how much of the disease
is occurring in a population? Uh, so sometimes you hear
some estimates of well, we have the prevalence, it, the prevalence
of a particular disease or obesity
in the U.S. is x-number. Um, so that simply means what’s the number
of existing cases of a particular disease? And that really helps us
to really determine whether we have
a public health problem and how do we
allocate resources? And populations. So, one of the interesting
things with epidemiology is that we’re focused
primarily on populations. We’re looking, for example,
at obesity in children, very concerned about studying that particular-
that population. What’s going on? What are the factors
that might increase the risk of obesity among children? So usually when
we think about populations we’re looking at a larger scale. We’re looking at what kinds
of policies can we develop to really make an impact, um, on a larger group
of individuals, a larger group of people. We aren’t specific,
only looking at one individual. Um, and then we
want to know, well, if we have a sense of
the patterns of the disease, we have a sense
of-of-of for example what factors are contributing
to that disease then we want to know
ultimately well, we wanna make sure that we’re tracking that over time, and this is where
surveillance comes into play. So you’ll hear me
talk about, um, I’ll show you some
statistics soon that is, uh, that are generated from
the Centers for Disease Control, our primary public health
organization in the-in the US where they take surveys
of the population over time because they wanna get
a sense of what’s going on. If we do know, for example,
that if people could be more physically active, are we finding that over time
if people, if the levels of physical activity
are increasing, are we finding that that
is having an impact on, uh, obesity by decreasing
the number of individuals that have the condition? Uh, and then we use this for, and this is where
my epidemiologic research comes in, we hypothesize,
for example, that if people
were to exercise more they would be less likely
to be overweight or obese. So when we think about
obesity, we certainly, we-we think of it as having
a higher amount of body fat in relation to body mass,
and this is typically based on what we call
the body mass index. Uh, for children we,
this is based on, uh, your, on the child’s, um,
age as well as, uh, so basically you’re comparing
them by their overall weight based on the age
and we look to see if they fall within
a certain percentile. So, if they’re overweight, uh,
that we’re usually looking at, uh, kids that are greater then
the 95th percentile and then at risk
for overweight would be in the, uh, greater than
the 85th percentile. So that’s for children. For adults,
when we look at BMI, uh, individuals that we’re
concerned about are people who have a BMI either, uh,
25 or above and then we also, and then we’re also very
concerned about people who would be, uh, very obese-uh,
either obese or severely obese and that can be either a BMI
greater than 30, for example. Uh, so how do we know,
so now that we have a definition in terms of how we
think about obesity, how we assess it
in populations, well, how do we know
that this is something we should be concerned about? So one way we do that,
we collect data and statistics and one survey that’s used
quite a bit, um, is the National Health, uh, a-and Nutrition Examination Survey that’s conducted by the CDC,
and this survey has been collected over time since the 1960s, and when we look at that data over time we find that after taking all these
cross-sections of populations we see that over time
the individuals with obesity are on the rise, especially when we look at men and women between 1960 to 2000. We’re seeing
a continuous increase in the number of individuals who are considered
overweight or obese. When we look at children,
very concerning, we see the same pattern. We look at kids or, for-for
the purposes of, uh, of uh, this discussion we’re
looking at children between, we’re defining children
between the ages of 2 and 19 between 1963 and 2008 so we
have several years of data where we can look at the trend and we see that over time there are increases
in every age group, whether you’re
in the 2 to 5-year-old, the younger age group-
the youngest age group through to
the 12 to 19-year-olds. So we’re seeing that
this is pattern; obesity is increasing over time. We have a standardized measure
where we’re collecting data and we’re seeing that
over time this is increased. Also, we wanna see, one of the things
that we’re concerned about, again, we talked about patterns. We talk about distribution. So we also look across
the entire United States, and these are
some statistics from 2013 where we see, for example, the, uh, part
of the-the southern, um, United States for example
we see higher rates, uh, of obesity and now finding
that most, uh, across the US we really aren’t finding,
uh, any states that have obesity rates
that are, say, under 20% and this is a concern. What is even more concerning
is that when we, when we look again
at these, you know, what’s going on in terms
of patterns, so geographically, we see what’s going
across the US but then we can
drill down even further, what’s going on with
partic groups, specific, uh, racial ethnic groups. And what’s concerning
is that when we look at the, the current, uh,
statistics from the CDC, at non-Hispanic blacks,
for example, we see overwhelmingly
that greater than 35% across almost all the states
of blacks are considered, based on their self reported
height and weight which we used to measure BMI that
they are also, um, uh, obese. So this is very concerning
when we think about what groups should we be targeting, what groups
should we be focusing on. Uh, we see
similar characteristics when we look at, uh,
Hispanic adults, uh, as well. Um, what’s even more
concerning is that when we look at children,
we look at data for children, we see some of the
same characteristics. So here we have
some information on, uh, another, a survey that’s
been done with children where we find that
Hispanic children, for example, 16% between-the youngest kids, between the ages of 2-5 considered uh-uh-uh obese, or we see the same thing-
and again concerns for, um, black children where again-
much higher rates when we compare them to, say, white children
or Asian kids. So again, this gives us
a sense of what are the patterns
within the populations? Which population should
we be focusing on? So why should we be
concerned, for example? So now that we see
the patterns and we, you know, we think
about the determinism, we-we then, we wanna think about well what kind of research should we be doing? Where should we be focused? And so one thing that I’m
particularly concerned about, one of the main reasons
that I am focused on childhood obes-obesity is that there has been
some research to show that if you are overweight
or obese as a child your chances of being
overweight or obese as an adult
increases significantly. So, as an example,
if you’re overweight or obese as a preschooler,
your chances of being overweight or obese,
um, as an adult is 35%. This is very concerning. And this is why, for example,
we find it really important to start working
with children earlier so that we can develop habits
that they can then carry on through adolescence
and adulthood that will then reduce their risk
for overweight or obesity. One of the other things
that is important from a public health
perspective, epidemiology is-so-is considered the science of public health, so we’re also
concerned about, well, what are the costs of obesity? You know, why, so again
thinking about the factors, we know that we see, again, we see obesity
increasing over time. We see higher rates
of obesity among, um, racial ethnic groups
within the US, and then we’re also concerned, well, wha-what does it mean if we have large groups
of people who have obesity? What does that mean
for the healthcare system? So here are some
estimates that were done, and these again,
I mean unfortunately were done in, uh, 2009,
um, showing that in 1998, uh, in terms of total cost
for obesity we’re looking at $78.5 billion per year in the US By 2008, ten years later that number had jumped,
had skyrocketed to $147 billion. So again, and what’s really concerning
is that Medicare and Medicaid. Uh, Medicare
where we support our elderly, Medicaid that’s primarily used
for low income individuals, that Medicare and Medicaid alone accounted for
42% of these costs. So again, showing that individuals that are vulnerable, individuals
who are lower income, elderly individuals, they are
going to be the ones that will need more care from us with respect to dealing, um, with the consequences
of obesity. So what can we do? So now that we-we-we,
you know, as a researcher, you know-well, here’s
this problem, what do we do? How do we use these principles
of epidemiology to address and to study obesity? So, going back
to the definition, so what we’ve done, primarily we’ve looked at
the distribution, um, within the US seeing, uh, high rates, uh,
in the southern United States. Uh, we’ve also
found that, you know, seen that in terms of
the disease frequency over time that it’s increasing, uh,
and that the population, some of the populations that
we’re really concerned about are racial ethnic
minority groups. So how then do we use
some of this information to apply what we’ve learned about, you know, about what we’ve learned
about obesity, how do we use that information now to control health problems, to control, uh, obesity? So let’s think back,
think to some of the- what are some of the-
so some of the principle targets that have come about
for obesity, uh, prevention and control and this is largely based
on some work that has been done, um, by
the Institute of Medicine. So some of the things that, uh, critical targets
one during pregnancy, uh, encouraging women to have
a healthy pregnancy weight. Be very careful in terms of
weight, uh, weight gain. Um, getting lots of sleep. Um, and I know that
can be difficult. As a college student of course you have alot of projects
to do, um, you know, and you’re trying to balance
so many things but sleep is really critical, um, in terms of, um, one, not only reducing
your risk for obesity but also doing well
as a student. Um, reducing energy intake. Increasing, uh, things
like physical activity. So these are-these are
just some, and then some other ones
you can read, but of course these are some
of the-the risk-the targets, important targets in terms
of reducing obesity risk. Um, then we think about, well-
what-how do we address this? Where-where do we
focus our efforts? And so there are
certain conceptual models that could be used
to study diseases, so one is
the social ecological model. There’s been shown,
um, where you-you sort of look at the individual
and you’re looking at what are some of
the interpersonal, institutional and larger
factors that work on that individual in terms of influencing,
um, their risk factors whentheir behaviors
or their risk factors when it comes to
particular conditions? And what we found is that
actually you have the greatest impact
when you work sort of above the individual, when you look at
those larger factors that might potentially influence, uh, obesity risk. So for example, having
policies, uh, to encourage, uh-uh-uh neighborhoods
that make it easier for people to walk, for example, um, has been shown
to be important in terms of reducing
obesity risk. We’re really finding that
if we work, if we have uh-uh, a poly-uh-broader policies
that can encourage and make it easier for people to engage
in behaviors that could reduce their obesity risk that we
actually have more impact instead of simply
focusing on an individual. So what are some settings,
so obesity treatment and, uh, for
prevention and treatment? So, early care
and education; for example, working with child care. Um, uh, working
in child care facilities. Um, ensuring that child
care facilities have, uh, good policies
with respect to healthy eating, um, working through school
lunch programs, for example. Um, we-uh-uh-workplace,
uh-uh-of-uh, programs that encourage, uh,
healthy eating, exercising, what-have-you. And some of the work that
I have done, for example, has looked at
the importance of green space, access to green space and how that potentially influences physical activity. So for example, we found
that kids who had more access to physical activity,
uh, were more aware- more likely to be engaged-
more access to green space were more likely to engage
in physical activity more-they were more likely
to be physically active. This is just one example in terms of policy recommendation that if we can increase access
to green space, for example, we can increase levels
of physical activity and hopefully longterm
reduce the risk of becoming obese
as an adult for children. Uh, these are just
some examples as well in terms of
where to focus our efforts, um, with respect to benefits, um, uh, looking at
cost effect benefits of specific, um, interventions. So for example, finding
that if we were to tax, if we were to focus on,
uh, television advertising, reduce that, um, that would
cost us eight cents for, per unit decrease in BMI. So doing things
like even having a soda, uh-x-uh, a tax on, uh-soup-
sugar-sweetened beverages, so these are
just some examples in terms of the-where we can- uh, -where we can
implement policies and then environmental polices and sort of giving us a sense
of the-the bang for our buck. How much would it cost us? How cost effective
are these policies? So moving forward,
and then the critical thing that I would like for you
to take from this is that epidemiology
has, uh, complimentary, uh, there-there are complimentary, uh, contributions when it comes to epidemiology. So we calculate disease
trends in populations. Um, we then, it’s important
for us to understand what’s going on with
the-the trends in the disease. We wanna make sure
we collect good data. Uh, but then it’s also important for us to think about, well, how do we communicate this to the public, to policy makers? How do we implement
policies to make sure that, well we have learned
from the data, we can make sure that
we make an impact on whatever condition it is
that we’re studying? In this instance
with respect to obesity, we want to make sure that
we have policies that can certainly impact
larger communities that are cost effective, um, and where we can get
community buy-in. So I really hope that,
at a minimum, you can answer the question, what is epidemiology, and I truly hope
that you have an appreciation for, um, using the principles
of epidemiology to study obesity. So, good luck.

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