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Flashcards in Obesity and Cancer Deck (21):
1

Obesity

-what is it
-what it is related to

-Is a condition where the natural energy reserve, stored in the fatty tissue of humans, is increased to a point where it is thought to be a significant risk factor in certain health conditions, leading to increased mortality
-excessive body weight shown to correlate with various diseases, particular cardiovascular disease, diabetes, sleep apnea and osteoarthritis.
-also considered risk factor for certain cancers

2

Energy balance

-what it is

-energy intake and output normally balanced under steady-state conditions
-only about 27% of energy ingested in food is used for functional purposes
-excess energy stored as fat*food intake is regulated in accordance with body's needs.
*body has powerful control systems to avoid a deficit (weaker systems to control an excess)
-due to history

3

BMI

BMI = mass(kg)/height^2 (m^2)

4

Prevalence of obesity over time

-has increased over time
-especially since 1980s due to emergence of fast food chains and the microwave

5

Obesity types (males and females)

-Is visceral and subcutaneous fat
-Men tend to have more visceral fat than subcutaneous fat
-women tend to have more subcutaneous fat

*visceral is more dangerous

6

BMI -> problems

*BMI is most widely accpeted calculation
-Has no meaning by itself
-cannot distinguish between fat mass, muscle mass or bone mass
-muscle is more dense than fat
-children have higher bone density = false BMI
-muscular atropy/osteoporosis in elderly isn't accounted for
-Caucasian women have less muscle mass and bone density than men of same height

7

Alternative ways to measure body fat

-% body fat
-for men, >25% is bad and women > 30% obese
-Underwater weighing (fat floats)
-Skinfold test (thickness of subcutaneous layer)
-Bioelectrical impedance (metal footpads that send small current through body)

8

Evolutionary aspects

-Food scarcity; take advantage of rare periods of abundance by storing energy
-is an evolutionary advantage = thrifty phenotype
-this is maladaptive in modern society with adequate food supplies
*many people have genetic propensity towards obesity, but this propensity requires a modern environment;
-increased food availability
-decreased requirements for physical labour

9

Society's flaws in promoting obesity

-lack of activity (due to modern convenience)
-lower relative cost of foodstuff
-increased marketing
-2 income households
-microwave oven
-increased no. of fast food outlets
-increasing affluence itself
-aging population (older ppl have slower metabolism)

10

Specific causes of obesity

-sedentary lifestyle
-high lycemic diet
-underlying illness
-genetic disorder
-psychological eating disorders
-stress
-psychotropic medications
-smoking cessation

11

Energy availability in foods

-proteins, carbohydrate and fat

1 g protein = 16.7kJ
1 g carbohydrate = 16.7kJ
1 g fat = 37.7 kJ
-Carbohydrate and protein usu. associated with large volumes of water in foodstuffs (75%), whereas fat is not

-fat is hydrophobic - doesnt associate with water

12

Endocrine mechanisms

-hormonal mechanisms have been shown to control appetite and food intake, storage patterns of fat and development of diabetes
-Leptin is produced by fat tissue to signal storage reserves in the body, and mediates long-term appetitive controls
-Ghrelin, produced by stomach, modulates short-term appetite control (obese ppl don't respond well to Ghrelin, as non-obsese ppl)
-many also thought to be leptin-resistant

13

Complications with Obesity

-Cardiovascular
-endocrine
-gastrointestinal
-Renal and genitourinary
-skin and appendages
-musculoskeletal
-neurologic
-respiratory
-psychological

14

Therapy
(3)

-Best treatment = energy-limited diet and increased exercise
-as little as 5% loss of body mass = enormous health benefits
-80-95% of ppl regain weight in 2 to 5 yrs
-is brain plasticity problem -> brain recognises weight as desired weight - results in yo-yo dieting
-after weight loss, need to reset brain pathways

-Also pharmacotherapy and bariatric surgery (staples)

15

Cancer

-is a class of diseases characterised by uncontrolled cell division and the ability of these cells to invade other tissues
-is caused by damage to DNA, resulting in mutationss to genes that control cell divison
-Mutations can occur spontaneously, caused by chemicals or physical agents called carcinogens, exposure to radioactive materials or can be passed down generations

16

Cancer -> effects

-Severity depends on site and character of malignancy and where there is metastasis (cancer cells transported through blood or lymphatic system)
-benign tumors are NOT cancer
-if untreated, may eventually cause illness and death -> not always the case
-Mainly affects those of later years, but can affect anyone
-is one of leading causes of death in developed countries

17

Cancer and lifestyle factors

-most forms of cancer are sporadic and have no basis in heredity
-most are related to known lifestyle factors;
-tobacco, diet, exercise, alcohol, tanning choices, sex
*20 year lag between tobacco use and cancer

18

Epidemiology of cancer

-Developed countries: cancer is overtaking cardiovascular disease as main cause of death
Developing countries; cancer incidence appears much lower, most likely b.c of higher death rates due to infectious disease

*cancer epidemiology closely mirrors risk factor spread in various countries

19

Carcinogens

*is any substance that promotes cancer
-many of those consumed by humans are produced by plants or fungi to prevent animals from eating them
-cooking protein rich food at high temps can lead to formation of many potent carcinogens
-Benzene, formaldehyde and asbestos are examples of industrial carcinogens
-all radionucleotides

20

Prevention of cancer

-avoiding carcinogens or altering their metabolism
-avoiding excessive alcohol consumption, being physically active and maintaining recommended body weight
-no tobacco exposure

21

Diet and cancer

-Obesity increases the risk of developing cancer
-different countries have different types of cancer -> suggests differences in diets is to blame
e.g. in Japan = gastric cancer
US = colon cancer
-study found beta carotene increases cancer risk slightly