body composition Flashcards
body composition
average comp of cadavers by dissection
female
fat- 43%
muscle- 28%
bone- 12%
skin- 5%
other-12%
male
fat-28%
muscle-39%
bone-14%
skin- 5%
other-14%
body composition measures
BMI- weight/height= measure of weight for height but mayy be elevated by increased fat or lean
fat mass (FM)- chemically defined fat, including essential fat, cna be expressed as FMI:FM/height^2
fat free mass (FFM)- everything else can be expressed as FFMI- FFM/height^2
why does fat content matter
main energy store- highly metabolically active
fat produces hormones including leptin and adiponectin- controls levels of blood lipids
inflammatory cytokines- tumour necrosis factor (TNFa) + interleukin-6 (IL-6)
immune modulators
mortality by cause to BMI
increased risk with overweight and obese for all types of mortality
most with CVD
both underweight and overweight are harmful
due to increased risk of
- hypertension
- CHD
- stroke
- oesteoarthritis
- varicose veins
- breast cancer
- endometrial cancer
- gout
optimal fatness
optimal BMI for lowest mortality at age 65+ to mildly obese (25-35)
BMI affected by loss of lean tissue and height loss
predictors of mortality in older people include- weight cirumference, low lean body mass
optimal % body fat:
- men= 24.1-29.4%
- women=42-46.4%
fat distribution
location and amount of fat has specific health consequences
as we age, body tends to mvoe and the fat metabolises differently in different places in the body
more adverse health consequences form abdominal than peripheral fat, visceral fat more than subcutaneous fat
measures of FD include- MRI or CT scan, waist cirumference, wasit to hip ration
waist:hip ratio
even in people of ideal weight, high W:H shows higher risk of hypertension than lower W:H
within a weight category, those with higher WHR has higher risk of hypertension and diabetes
normal weight, WHR >0.8 had same fiabetes risk as >50% overweight and WHR <0.73
metabolic syndrome
formerly known as syndrome X
ATP III identification of the metabolic syndrome
features inlcude
- abdominal obesity
- triglycerides >150mg/dl
- HDL cholesterol (men=<40, women <50)
- blood pressure >130/85mmhg
- fasting glucose >110mg/dl
pre cursors for diabetes and risk factors for CVD
visceral fat
has particularly adverse effects for a number of reasons
- more metabolically active- produces more cytokines
- greater response to sympathetic stimulation eg stress
- releases fatty acids into portla vein which goes straight to liver
- increased hepatic production of LDL and increased gluconeogenesis- formation of glucose
- less leptin produced by visceral fat- signal of fullness, increasing drive to eat
visceral fat effects
angiotensin II- raises BP
high BP- stroke/CVD
clotting intermediates- fibrinogen and plasminogen which can block blood vessels
adiponectin- maintains healthy levels of blood lipids
atherogenic- leads to atherscelorosis
all linked in a cycle
mean height and age
mean lose an average of 12cm between age 30-80 years
people born in 1920s were smaller than those born in 1980s
mean weight and age
heaviest people age 45-54, older are lighter but also smaller in height
mean BMI
BMI increases from middle to old age
individuals lose height meaning the BMI will increase so it may not be an accurate measure
obesity
middle age is highest for obesity/overweight
highest waist cirumference is always increase with age
WHR- men (apple shaped) seem to have higher than women (pear shaped)
differences in fat distribution with age
reduced ability to store subcutaneously
reduced skinfold thickness and hip circumference
greater proportion of fat stored viscerally
increases waist circumference- particulalry in women
adverse health outcomes- hypertension, insulin resistance, increased inflammatory cytokines
