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Aging and Body Composition.docx

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McMaster University
Krista Howarth

Aging and Body Composition Body Dimensions (I) Height  On average females are shorter than males. We also see that females reach their peak height sooner than males ( 16-18 yrs old). Males reach their peak height at about 20 years of age.  Females start loosing height before males.  At age 60-70 yrs women will lose height at a more rapid rate than men  Men loose 4% their height by the age of 70  Percent height loss is similar between males and females, however, women start at a smaller base height => loos of height is greater  Menopause: o Osteoporosis  Much more rapid decline of bone mineral density in women because of menopause (loss of estrogen)  Small fractures in vertebrae because of decreased bone mineral density  Over time vertebrae fractures accumulate into more forward posture ( a hunch) these fractures are more likely to happen on the anterior side of the vertebrae => leads to kyphosis o Vertebral disc compression  Accumulation of gravity over time  Vertebral disks make up 20-30% of total length of the spine o Other determinants of height  People tend to loose a little bit of their foot arch (loss of strength of ligaments and muscles)  Start to loose muscle tone as you get older (muscles help us stand up straight. Loss of muscle results in slumped posture)  Peak height determined by genetic and environmental factors  Living in the altitude more stress on the body ( muscle and bone)  Change in hormonal level because of exercise=> has impact on overall bone density  Disease (II) Wight  Females: gradual increase in weight until approximately 5 decade, weight then plateaus for a couple of decades, then slowly start to decrease  Males: similar pattern to females, but decline in body weight starts a bit sooner o Late 30s-40s are stable. o Weight starts to decline in late 40s  Females continue to rise in body weight longer and keep the same body weight for longer.  Males plateau at about 40-50  Body weight decline due to: o Decline in muscle mass o Decline in bone mass  Unusual or sudden weight loss in elderly may reflect health problems o Cancer o Emotional health problems (III) BMI  Gender difference in when peak BMI generally occurs o Eg. Males – between 45-49yrs o Eg. Females between 60-70yrs  BMI has a complex relationship with mortality risk, depending on age  Different health risk associated with high or low BMI’s  Initially males have increase in BMI and then decrease after 40-50 years of age  Females increase until about 60 and then decline  Females are keeping/gaining weight longer, but they are loosing height sooner => raising their BMI number  BMI associated with the lowest risk of mortality is going to change with age  High BMI => CVD, diabetes, hypertension  Low BMI=> osteoporosis (linked to frailty and risk of fractures => especially for women) respiratory and GI illness  Typical range for young individuals is 18.5-25  As you age BMI associated with lowest risk of mortality increases Body Composition  2 main compartment: o fat mass and fat-free mass ( muscle, bone, water) o body composition is influenced by genetics and environment (I) Total Body Water  Approximately 60-65% of body composition is water 9depends on percentage of body fat)  Percent body fat dictates how much water your body holds o Fat is hydrophobic o Do not store water in fat o Only about 20% of fat is water o 70% of muscle is water o if you have more fat-free mass you have more water  Body water decreases linearly with age
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