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Lecture 7

Kinesiology 1080A/B Lecture Notes - Lecture 7: Twin Study, Aerobic Exercise, The Takeaway

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Kinesiology 1080A/B
Bob La Rose

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Tuesday, November 7, 2017
Lecture 7
What is Obestiy?
- TedEd Video
o BMI breaks down body fat
o Oesit a oditio he a persos od fat is oer 30%
o Body fat percentage can be accounted for muscle mass
o Obesity caused by energy input greater than output
o Combo of choices
WHO Definitions
- Overweight and obesity are defining as abnormal or excessive fat accumulation that
may impair health
- Classifications are based on body mass index (BMI)
o Talking about how it affects health in an adverse way
- 55 and 145
- limitation: it is an estimate category it is a range and if you gain you can be bumped
into another category
- dotors a e a hart
- weight in kg divided by height (kg/height m2)
- underweight = <18.5, Normal 18.5-24.29.9, Overweight 25-29.9, Obese >30
o older people and super muscular people, pregnant women, people with certain
disabilities would be a disadvantage
o works greater on a population level than individual
A good Estimate or Not
- athletes especially those who have a lot of muscle mass
- older people
- preggo
- individuals with eating disorders
- individuals with disabilities
Beyond BMI
- waist circumference and waist to hip
- Apple vs. Pear shape
- Measurement issues
o Depending on what organizations you look at may differ how to measure the
o Not that these measures are better or worse than BMI, they are associated with
BMI doest ea it is a perfet relatioship
- Body Composition
o Skinfold thickness
o Bioelectrical impedance
o Duel energy x ray absorptiometry (DEXA)
o Densitometry (hydrostatic weighing, air displacement)
What Causes Obesity?
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- Carbs, protein and fat = energy in
- RMR, Physical Activity, TEF (thermic effect of food) = energy out
Not to suggest that obesity is a matter of over-eating
- Look at is it a slow metabolism?
o Obesity is not caused by a low resting metabolic rate
o Usually they have higher MR because they require more energy to sit at rest
Energy In
- Hormones affect appetite and food intake
o Leptin
o Ghrelin
o Cholecystokinin
o Glucagon-like peptide 1
o Oxyntomoudlin
o Pancreatic polypeptide
o Peptide YY
Physical Inactivity as a Risk
- the Big To = lo leels of PA ad high leels of food itake
o additional environmental influences like living in climate control places (where
warm climates work to keep you warm), sleep (affect apatite and metabolism),
smoking which effects appetite and energy intake
- association between low levels of PA and increased obesity risk
o low level associated with higher risk
- high levels of PA associated with lower weight gain overtime
o much of what we know comes from self-reports where people over report their
exercise and under-report their weight
- maintainers exhibit far greater energy expenditure than gainers
- what about diet?
o The relative contributions remain uncertain and may differ between individuals
and even within individuals over time
- Reverse causality
o Is obesity causing people to exercise less? Or vice versa
Genetic Influences
- Adoptio studies: adoptees eight status losel assoiated ith that of iologial ot
adopted parents
- Twin studies: sets of overfed twins gained weight consistently within pairs, but with
variation across pairs of twins (100 days/84,000 kcal = 4.3-13.3kg gain)
How prevalent is it?
- Worldwide obesity has doubled since 1980
- 24.8% Canadians >18yrs were obese in 2011-12
- 6.3 million people
- 17.5% more than in 2003
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