Food and Cancer- L8

Question 1

What is the median body mass index for adults ?

Answer 1

between 21 and 23

Question 2

What is the link between being overweight and cancer?

Answer 2

convincing evidence that being overweight/obese increases the risk of many cancers including bowel and breast cancer

Question 3

What are the recommendations about body fatness?

Answer 3

ensure that throughout childhood and adolescent that your BMI is towards the lower end of normal
maintain BMI within the average range throughout adulthood
try to avoid weight gain and increased waist circumference during adulthood

Question 4

Which cancers have convincing links with body fatness?

Answer 4

• oesophageal
• pancreas
• colorectal
• breast
• endometrium
• kidney

Question 5

What cancers have convincing links with abdominal fatness?

Answer 5

colorectal

Question 6

What are the BMI scores?

Answer 6

40= grade 3 overweight- morbidly obese

Question 7

What are the limitations of BMI ?

Answer 7

• doesn’t directly measure body fat
• limitations based on differences in sex, age, ethnicity and atheletic experience
• • women tend to have higher fat content than men
• • BMI overestimates body fat in persons who are very muscular
• • BMI can underestimate body fat in persons who have lost muscle mass e.g. elderly

Question 8

What are the different methods of assessing the percentage of fat and lean mass ?

Answer 8

• water or air displacement
• dual energy x-ray absorptiometry
• bioelectrical impedance
• skinfold thickness measures

Question 9

What was the link in men between body fatness and oesophageal carcinoma ?

Answer 9

from 5 different studies large increase in risk associated with a higher BMI
- each increase in 5 BMI units increases the risk of cancer by 52%

Question 10

What is the link between lung cancer and oesophageal squamous cancer and BMI?

Answer 10

strangely it demonstrated that increased BMI reduced risk of these cancers

Question 11

Which female cancer is most strongly linked to BMI?

Answer 11

cancer of the endometrium - there is very little variation - barely any confidence intervals

Question 12

What happens with BMI and breast cancer risk ?

Answer 12

premenopause- increased BMI reduces risk of breast cancer
postmenopause- increasing BMI increases risk of breast cancer

researches think there are 2 different aetiologies driving breast cancer before and after menopause

Question 13

What type of breast cancer is most common ?

Answer 13

postmenopausal breast cancer is most common - strong links with estrogen status which is associated with fatness

Question 14

What is a major worrying aspect about the link between BMI and cancer ?

Answer 14

Although the increase in risk per 5Kg/m2 increments are modest, the numbers of incident cases attributable to excess BMI might be substantial as the prevalence of overweight and obesity is icnreasing in many countries

Question 15

What has happened between 1993 and 2009 in relation to fatness?

Answer 15

in both men and women there has been an increase in obesity

Question 16

What is abdominal fatness and what increased risks does it cause ?

Answer 16

it is associated with health risks such as CVD
the waist circumference can be measured and used as an estimate for abdominal or visceral fat
could be a better indicator of health risks than BMI alone

Question 17

How is waist circumference measured ?

Answer 17

measuring waist circumference is midway between the uppermost border of the iliac crest and the lower border of the costal margin

Question 18

What has happened to waist cicrumference of men and women between 1993-2009?

Answer 18

it has increased in both, however more substantially in women

Question 19

What did a study looking at waist circumference and mortality demonstrate ?

Answer 19

Low WC but obese= doesn’t increase risk of mortality
High WC but not obese= increased risk of mortality
High WC and obese= Increased risk of mortality but only slight more than high WC and not obese

therefore having a high WC and not being obese is very detrimental

Question 20

What different results were shown in colon cancer when different measurements of fat were used?

Answer 20

ABDOMINAL OBESITY
- increased risk factor for colon cancer in both men and women

BODY WEIGHT and BMI
- increased risk factor for colon cancer seen in men but not in women

Question 21

Why is it not necessarily a good idea to do self-reported data for looking into association between weight and cancer risk ?

Answer 21

people will lie about their weight and therefore when self-reported dat and measured data results are compared there are differences

Question 22

What does BMI reflect ?

Answer 22

reflects both lean and fat mass

Question 23

What has recently bean indicated as an equivalent or stronger predictor of cancer risk in adults in comparison to BMI?

Answer 23

weight gain - it largely reflects increase in body fat independent of BMI

Question 24

What is the link between height and cancer?

Answer 24

the taller a woman is the greater risk they have in developing post menopausal cancer - could be linked to growth rates during childhood

Question 25

Why is weight very important in postmenopausal women ?

Answer 25

data suggests that advising women to lose/maintain weight after menopause may reduce breast cancer risk

• women who lost weight after menopause had a reduced risk of breast cancer - 40% reduction
• gaining weight after menopause is very detrimental, increases breast cancer risk

Question 26

What happens when weight is lost after menopause?

Answer 26

weight loss lowers circulating oestrogens
- these hormones are directly related to the risk of breast cancer so weight loss is suspected to decrease risk - not consistently shown

Question 27

What potentially can intentional weight loss in obese cause ?

Answer 27

might protect against malignancy but the evidence is limited
- swedish obese subjects
- 2010 obese patients - had bariatric surgery
- 2037 match obese controls had dietary controls
those that had surgery had lost about 19+ Kg whereas other group slightly gained weight
the surgery was linked to reduced risk of in cancer for women but not for men

Question 28

What are the 3 candidate systems in which obesity increases cancer risk ?

Answer 28

• insulin and insulin-like growth factor-1 axis
• sex steroids
• inflammation

Question 29

What is the insulin cancer hypothesis ?

Answer 29

excess body weight leads to increased insulin production and leads to hyperinsulinaemia and insulin resistance
- the increased IGF proteins leads to increased IGF1 which increases tumour development

Question 30

What is the link between sex steroids and cancer risk ?

Answer 30

• adiposity influences synthesis and bioavailability of endogenous sex steroid
• relationship between obesity and breast cancer risk post menopausally may be largely explained by increased levels of oestrogens particularly bioavailable estradiol from adipose tissue

Question 31

What happens to the levels of estradiol throughout a women life?

Answer 31

levels are maintained high throughout the reproductive lifehood of a female but after menopause levels drop to very low due to ovarian function declining therefore any increased levels will be due to adipose tissue

Question 32

How is increased endogenous hormones linked to breast cancer ?

Answer 32

higher circulating levels of oestrogen is associated with increased risk of breast cancer

Question 33

What is suggested as the causative factor of breast cancer?

Answer 33

increased levels of estradiol- these levels will be increased in women with a higher BMI due to greater fatness

Question 34

What is obesity characterised as ?

Answer 34

it is a low grade chronic inflammatory state

Question 35

What inflammatory factor is increased in obese people?

Answer 35

increased circulating levels of tumour necrosis factor alpha, interleukin-6 and c-reactive proteins in comparison to lean people
- such chronic inflammation may contribute to the development of cancer- favours tumour development/progression

Question 36

What are examples of cancer specific factors which increase risk ?

Answer 36

oesophagus (adenocarcinomas) and gastric cardia

• these cancers are difficult to differentiate between
• obesity causes reflux, barretts oesophagus and inflammation - more closely linked to abdominal obesity
• the contents of the stomach can be regurgitated up the oesophagus damaging the lining of the oesophagus - if this happens often then pre tumour state can occur when

Question 37

Why is important to limit consumption of energy dense foods ?

Answer 37

because they increase obesity which increases risk of cancer

Question 38

what are the public health goals associated with energy dense foods?

Answer 38

average energy density of diets to be lowered towards 125kcal per 100g
population average recommended consumption of sugary drinks to be halved every 10 years

Question 39

What factor shows good evidence for protecting against cancer?

Answer 39

physical activity

- e.g. breast cancer and bowel cancer

Question 40

What are the personal recommendations for levels of physical activity?

Answer 40

be moderately active every day(brisk walking) for at least 30 minutes
as fitness improves aim for 60 mins moderate exercise every day or 30 mins intense
dont be sedentary for most of the time

Question 41

How does physical activity reduce the risk of cancers ?

Answer 41

by reducing fatness
endogenous steroid hormone metabolism
potentially strengthen immune system
reduce circulating levels of oestrogen and androgens

Question 42

Although there is an association between many different factors and cancer what is the most substantial ?

Answer 42

the link between smoking and lung cancer is far more substantial than any other factor