Vienna: Cancer is more likely to develop in people who are very overweight
(obese), because surplus body fat interferes with various hormone cycles
and with glucose and fat metabolism. Metabolic expert Alexandra
Kautzky-Willer at MedUni Vienna and
Vienna General Hospital, draws attention to the fact that, even in
Austria, more and more people are suffering from obesity. Several
studies are therefore being conducted at CCC to investigate the links
between obesity, metabolic disorders and cancer. Obesity is
very much on the increase in industrialized countries. Currently 15% of
men and 10% of women in Austria are morbidly obese. The latest studies
show that young women and postmenopausal women are particularly affected
by this negative trend. Adults are regarded as being obese if they have
a Body Mass Index (BMI) of more than 30. A BMI of between 18.5 and 24.9
is considered normal but, at a BMI of more than 25, you are considered
to be overweight.
Abdominal fat is particularly dangerous
New
data from an international study, which was published in Lancet
Oncology in 2015, show that 5.4% of all cancers in women and 1.9% of
cancers in men are associated with a high BMI. This is particularly true
of cancers of the oesophagus, bowel, kidneys, pancreas and – in women –
the gallbladder, ovaries, uterus and postmenopausal breast cancer.
Endocrinologist and consultant in gender medicine, Alexandra
Kautzky-Willer, Vice Principal of the University Department of Internal
Medicine III of MedUni Vienna and member of the Comprehensive Cancer
Center (CCC) Vienna: "People with a BMI of 30 and above are
predominantly affected. An increase in BMI by only a factor of 1, for
example from 29 to 30, increases your cancer risk by between 3% and 10%
for the said types of cancer. Particularly abdominal fat, also known as
visceral fat, has a negative impact on health, since it increases your
cancer risk and encourages the development of metabolic disorders such
as diabetes, or cardiovascular disease."
Fatty deposits in the
abdominal area increase the cancer risk for several reasons: first of
all, fatty tissue is hormonally active, produces adipose tissue hormones
and changes the balance of sex hormones – for example by converting
more androgen precursors into oestrogen. This encourages the development
and growth of hormone-related tumours, such as various forms of breast
cancer or endometrial cancer. The detrimental shift in the balance of
sex hormones and adipose tissue hormones directly and indirectly
encourages tumour growth. It also leads to an increase in insulin
resistance, which the body responds to in turn by increasing insulin
production. Kautzky-Willer: "The problem with that is that insulin not
only regulates the metabolism but can also act as a growth-stimulating
hormone and encourage cell division and hence tumour growth. We can
therefore see a close relationship between diabetes and certain types of
cancer, in particular liver and pancreatic cancer. High blood sugar
levels also seem to further promote tumour growth." Another aspect is
that chronic inflammatory processes can occur in the region of the
abdominal fat and these also favour the development of cancer.
Kautzky-Willer: "The positive thing is that you can do something about
this risk by losing weight or keeping an eye on your weight from the
outset. Many types of cancer could be easily avoided in this way; a
Mediterranean diet and exercise also help."
Further research into the links
At
the Comprehensive Cancer Center (CCC) of MedUni Vienna and Vienna
General Hospital they are conducting further research into the links
between obesity, diabetes and cancer. For example, the CANDY study
(CANCER AND DIABESITY) has been set up. This looks at the link between
diabetes and tumour diseases. Other studies are investigating the
influence of various diabetes drugs on the development of cancer and the
course of the disease. This should help to further improve drug
treatments.
Abdominal girth a better marker than BMI
Although,
even in scientific publications, the BMI is commonly used as a guide
value, experts only regard it as a general marker. Kautzky-Willer: "The
BMI relates to body weight and makes no distinction between fatty tissue
and muscle mass. So, for example, a bodybuilder, who is very heavy
because of his muscle mass but hardly has any fat at all, would have a
very high BMI. Abdominal girth, on the other hand, is a much more
reliable indicator of overweight or obesity, because it can be used to
specifically determine the proportion of fatty tissue."