Explain Changing Body Composition with Ageing?
With ageing, a progressive decline in the water content and the lean body mass is accompanied by an increasing proportion of body Tat. By 80 years, it is estimated that only half of the muscle cells remain. Specific functioning cells are replaced in part by non-specific fat and connective tissue.The changes in connective tissue, which is so abundant in the human body, are of special significance. Collagen is one of the fibrous materials found in tendons, ligaments, skin and blood vessels. With ageing, the amount of collage increases and it becomes more rigid, the skin loses its flexibility, the joints creak and the back becomes bent.
There is an average loss of 6.3% lean body mass for each decade of age and the same is compensated by an increase in the body fat and slight rise in body weight. The presence of chronic calorie deficiency also accelerates the loss of lean body mass.Both longitudinal and cross-sectional studies throughout the world, indicate that height Decreases with age. The average reduction in height during the total life span is about 2.9 cms in men and 4.9 cms in women, with approximately half the decrease being in sitting height. The reduction in sitting height is a result of vertebral compression, Change in shape and height of vertebral discs, loss of muscle tone and postural changes.
A decline in weight has also been observed with advancing age, but the pattern of change is different from that of height and varies by sex. Weight loss in elderly is generally caused by a reduced lean body mass (LBM) and body fat due to metabolic and physical changes associated with ageing or presence of disease conditions. The body water content reduces with advancing age and this has been implicated as an important cause of decline in weight after 65 years.
The affluent populations in the Western countries show an increase in average weight both in men and women in the middle age. In men, this weight gain plateaus at around 65 years and then declines. Among women, however, the weight gain is greater and the plateau occurs about 10 years later than in men. The data on underprivileged populations is limited.
Cross-sectional studies also show a slow, progressive redistribution of fat in the elderly. The body fat relocates centrally and intra abdominally, while the subcutaneous fat on the limbs tend to decrease. An increase in abdominal circumference with age many also reflect shortening of trunk due to osteoporosis or other spinal deformities. As the length of the trunk decreases, the abdomen increases in girth.