Vanessa Benham, for the Lansing
State Journal
Published 4:02 p.m. ET April
30, 2019 | Updated 8:37 p.m. ET
April 30, 2019
LANSING, Mich. – You probably know smoking
causes cancer, maybe even that it's the leading preventable cause of cancer.
You might not know the second leading
cause of cancer, because scientists have only recently made the
connection.
It's obesity.
Researchers have been investigating a
link between obesity and cancer for more than 15 years, but that link
was only established conclusively in the past few years.
While public health officials have programs
that address both obesity and cancer prevention, they haven’t tailored programs
to specifically address obesity as a cancer risk factor.
They’ll have to.
Because of decreasing smoking rates and
increasing obesity rates, obesity is predicted to surpass smoking as the No. 1
preventable cancer risk factor within the next two decades.
It’s already a public health concern in
Michigan, which has the 10th highest adult obesity rate in the nation.
More than 32% of the state’s population is
obese. That rate was as low as 25% in 2003. It has been rising steadily.
As it does, obesity-associated cancers are
expected to increase. And the risk, at least according to some studies, is
higher for African Americans.
“The risks for certain obesity-related cancers
in younger people is higher in today’s generation of young people than it was a
couple generations ago,” said Kristen Sullivan, director of nutrition and
physical activity for the American Cancer Society. “We don’t know exactly where
the risk is coming from, but a probable explanation is that we’re starting to
see the results of the obesity epidemic.”
Doctors and researchers have made immense
progress in treating cancer over the past three decades. A rising tide of
obesity-related cancers could roll back some of those gains, “which would have
critical implications for the health care systems.” Sullivan said.
“Right now, we are seeing a year-after-year
decline in overall cancer rates and cancer death rates, and that’s been
happening since 1991,” she said. “If that stops declining and (starts) going
up, more people getting cancer, more people dying from cancer starting at a
younger age, that would tax the health care system enormously.”
Obesity linked to 13 kinds of cancer
The first large-scale study to characterize
obesity’s association with cancer was published in 2003. It was an extensive
investigation of the relationship between body-mass index and the risk of death
from cancer.
Beginning with over a million participants in
1982, the study spanned 16 years, and it showed an increase in body weight was
associated with increased death rates due to cancer.
“As of right now, excess body weight or
obesity are linked to 13 different types of cancer," Sullivan said, “and
probably more cancer types will emerge as we continue to do more
research."
Among those linked to obesity are
ovarian, thyroid, uterine, pancreatic, colon and postmenopausal
breast cancer.
Researchers are still working to understand
exactly why. The relationship is complex, and experts are investigating a
number of possible mechanisms.
One likely culprit? Belly fat
Many believe the link lies somewhere in the
changes that happen in belly fat, what’s known as visceral adipose tissue in
the abdomen.
Belly fat is more than just an energy store.
It produces hormones and factors important for a person’s health. However,
having too much fat can increase or decrease the amount of hormones, proteins
and growth factors produced, which collectively increases health risks.
“There
are a number of different processes in the body that are related to excess
body weight that are probably contributing to cancer risk.” Sullivan said,
“They (can) impact levels of certain hormones like insulin or estrogen. And we
know of those hormones (that) elevated levels can increase risk for certain
types cancers.”
Changes in the belly fat of obese individuals
are likely connected to many of the other serious health conditions associated
with obesity, including cardiovascular disease, type II diabetes and metabolic
syndrome, which is a combination of high blood pressure, high blood sugar,
excess belly fat and abnormal cholesterol levels.
The obesity epidemic is changing the way we
look at these diseases.
Obesity, type 2 diabetes and cancer
Take, for instance, type 2 diabetes, which is
strongly associated with obesity. In many cases, the problem isn’t that the
body isn’t making enough insulin, a hormone that regulates sugar in the blood,
but that the body doesn’t recognize the insulin it’s making.
“For type II, you actually see higher insulin
production, higher levels in the blood,” said Dr. Cathy Jen, a professor in the
Department of Nutrition and Food Science at Wayne State University whose
research focuses on obesity and chronic disease.
And insulin resistance is a potential cause of
cancer, she said. High insulin and insulin resistance will promote the
production of a hormone called insulin-like growth factor 1, which regulates
cell growth on the one hand but can also stimulate the growth of cancer
cells.
But the relationship between obesity and
cancer isn’t that simple.
Scientists have shown hormone production and
inflammation can also contribute to cancer formation, and
researchers still do not know precisely how obesity causes cancer.
It’s not all about weight loss
You might assume the solution to the obesity
epidemic would come down to losing weight.
Weight loss doesn’t hurt, but increasing
physical activity and healthy eating improves health outcomes, whether you lose
weight or not.
“It is the sedentary lifestyle that is more
detrimental than not being physically active.” Jen said, “increase of physical
activity even without body weight loss will improve insulin sensitivity, reduce
insulin resistance and that will reduce insulin-like growth factors and that
will reduce the stimulation for cancer growth.”
Minorities have higher obesity, cancer rates
Studies have shown that the environment plays
a big role in promoting or combating obesity.
“In Detroit, for most people, the public
transportation is not great. If they don’t have a car they cannot go to
well-stocked supermarkets,” said Jen.
“So people without cars just go to the corner
stores or gas stations. And what kind of products do they sell there? High-fat,
high-calorie chips, long shelf life type of products, so people are more
likely to consume high fat, high sugar, high-salt, and high-calorie products.”
“At the
same time the walkability in Detroit, for inner cities, is low because people
are afraid to walk.” Jen said.
It adds up to huge health disparities. And,
for reasons bound up with issues of race and poverty and how both
affect where people live, those disparities fall disproportionately
on minorities.
“In inner cities like Detroit, the minority
population has higher obesity rates and have higher cancer rates.” Jen
said.
No big policy changes yet
The discovery of the obesity-cancer link is
too new to have led to big policy changes.
Which is part of the reason why programs meant
to combat obesity in Michigan fall under the cardiovascular branch of the state
Department of Health and why the cancer division doesn’t directly address the
obesity-cancer link
“Our section will work on promoting cancer
awareness and prevention,” said Courtney Cole, the cancer prevention consultant
at the health department. “We don’t work specifically on any programs that
address obesity, but a lot of the programs we do offer focus on those risk
factors such as diet and physical activity, and we do have direct service
programs within our section.
Michigan’s health department was already
treating obesity as a public health issue, working from the notion that obesity
is not just a result of individual choices, but also a product of
environment, of access to transportation and healthy food and places to
exercise.
“Our work is framed around changes to policy
and changes to the environment,” changes to the system that will support
healthy eating and physical activity, said Gwen Imes, the unit manager for the
Nutrition, Physical Activity, and Obesity Program of the Michigan Department of
Health and Human Services.
Changing the environment
“Let’s say the community has a city park, but
the park doesn’t have good lighting or the park doesn’t have any benches for
people to sit down or it’s not safe. So we might engage law enforcement to work
with us on a community level. Those are considered environmental changes, and,
by making those changes, then we can say ‘OK, for those people in that area
they can be physically active if that’s their choice.”
The program is also working with “people who
specialize in developing biking paths and connecting trails and make it not
only accessible but to make it safe for people to bike and walk.” said Loren
Disha, a consultant for the Obesity Prevention Program. “We are improving parks
and connecting them.” Making parks accessible and safe increases the physical
activity of a city’s residents.
They’re also working to expand access to fresh
fruits and vegetables.
“We fund work that makes fresh fruits and
vegetables available in corner stores,” Disha said, “so that people who don’t
have access to grocery stores or farmers markets are still having access to
fresh fruits and vegetables.”
“We recognize that people don’t have the same
starting place, so we want to make sure that everyone has an opportunity.”
Fresh veggies at Quality Dairy
One of the first corner store projects began
in Lansing in 2006.
“We convinced Quality Dairy,” said Peggy
Vaugh-Payne, the executive director for the Northwest Initiative, a nonprofit
organization that works to strengthen and sustain healthy communities in the
north and west sides of Lansing. “We started with one right on Pine and
Saginaw.”
“We went from one store the first year
to four stores a year and a half later, to 11 stores.” Vaughn-Payne said. “So
obviously it worked out.”
Through the project, the corner stores stocked
fruits and vegetables, increasing access for people in the surrounding
neighborhoods.
But without the Northwest Initiative
facilitating the program, it ended.
“The core of Lansing doesn’t have, and hasn’t
had for 25 years now, a full-service grocery store,” Vaughn-Payne said.
A Meijer-owned store is set to open in the 600
block of East Michigan Avenue but not until 2020.
And so Northwest Initiative sets up shop in
the basement of the First Presbyterian Church on North Ottawa Street every
Thursday for their Emergency Food Distribution events.
Additionally, Kevin Kortas, the outreach
manager at Northwest Initiative, and Vaughn-Payne piloted a new distribution
method in the form of a mobile farmers market last summer to increase
access to healthy options like fruits and vegetables.
“Every community that we went to said
essentially the same thing of ‘we would not have been able to get to the
grocery store to select these products without you being here,’” Kortas said.
“Time and time and again that was the story we heard.”
How much weight do I need to lose
The relationship between obesity, healthy
lifestyle and the environment is complex and not fully understood.
But, for those who want to reduce their cancer
risk, “Physical activity in and of itself is an amazing thing to for your
health and to reduce cancer risk, even if it doesn’t necessarily result in
weight loss” Sullivan said.
Reducing your risk of cancer lies more with
living a healthy lifestyle than the number on a scale.
In the meantime, experts say, the standard
advice on diet and exercise applies: stay active, don't take in more calories
than you burn through activity, choose whatever healthy diet you can stick
with.
“It really doesn’t matter if you do high-fat
or low-fat, high-carb or low-carb diet,” Jen said. “It doesn’t matter. The key
point is to reduce caloric intake and the longer you stick to the diet the
better the outcome.”
Vanessa Benham is a doctoral student in the
Department of Pharmacology and Toxicology at Michigan State University.
https://www.usatoday.com/story/news/health/2019/04/30/obesity-linked-thyroid-liver-kindey-ovary-pancreas-colon-cancer/3630418002/?_lrsc=351eb5f4-7585-485a-a72c-280ce5d40281&cid=soc-linkedin-elevate
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