Body Composition, Metabolic Syndrome and Testosterone in Aging Men

C A Allan; B J G Strauss; R I McLachlan

Disclosures

Int J Impot Res. 2007;19(5):448-457. 

In This Article

Body Composition and Ageing

In western populations body mass index (BMI) increases with age throughout adult life until approximately 65 years, after which time it plateaus and then decreases.[14] The ageing process is associated with a decline in lean body mass and an increase in FM.[15] Total body potassium studies show that between 25 and 65 years of age, a man will lose 12 kg of lean body mass, at a rate of 0.4 kg per year beyond the fifth decade, with a similar increase in FM[15] and no appreciable change in overall weight. The loss of lean body mass represents a 20% decline between 25 and 65 years of age,[15] with skeletal muscle lost more rapidly than non-skeletal muscle mass.[16] This degree of change has been confirmed in other healthy cohorts.[8] Skeletal muscle mass is preserved until the fifth decade, and thereafter the age-associated loss is greater in men than in women.[17] The increase in FM represents a 60--85% increase over the same time period; the overall percentage of body fat increases from 19 to 35%.[8,15,18] The distribution of the FM also changes, with a more central accumulation in men after puberty, and therefore this gain in FM is predominantly reflected by increasing abdominal adiposity. Furthermore, it appears that it is the visceral adipose tissue component (measured by computerized tomography (CT) scan) that continues to increase as a function of age,[19] while the abdominal subcutaneous FM plateaus after the age of 30 years.[17,18] The strongest anthropometric correlation with this intra-abdominal fat is waist circumference.[20]

The decrease in BMI after the age of 65 years reflects loss of both lean and FM, with further central redistribution of adipose tissue.[14] Others have described an accelerated loss of lean body mass after the age of 60 years, while FM continued to increase for another decade before it began to decline.[16] There is marked inter-individual variability in these changes[21] which in turn are influenced by alterations in total body weight.[22]

The relationship of endogenous testosterone to body composition and the ability to intervene with the administration of exogenous testosterone is discussed below.

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