Body composition of spinal cord injured adults.

The prevalence of diseases associated with obesity, such as cardiovascular disease and diabetes mellitus, is higher in the spinal cord injury (SCI) population. Specifically, the mortality rate for cardiovascular disease is 228% higher in the SCI population. In addition, 100% of SCI individuals have osteoporosis in the paralysed extremities. These diseases are related to physical activity level, the level of the spinal cord lesion, and time post injury. Physically active SCI men and women have above-average fat mass (16 to 24% and 24 to 32%, respectively, compared with 15% for able-bodied men and 23% for able-bodied women), while sedentary SCI individuals have 'at-risk' levels of body fat (above 25% and 32%, respectively). The proportions and densities of the 3 main constituents comprising the fat-free body (mineral, protein and water) are altered following SCI. Bone mineral content decreases by 25 to 50%, and the magnitude of reduction is dependent on the level, completeness and duration of SCI. Because of denervation resulting in skeletal muscle atrophy, total body protein reduces by 30%, and total body water relative to bodyweight decreases by 15% following SCI. Indirect methods based on 2-component body composition models assume constant proportions and densities of mineral, protein, and water in the fat-free body. As a result, prediction equations based on 2-component models yield invalid estimates of fat and fat-free mass in the SCI population. Therefore, future research needs to directly quantify the proportions and densities of the constituents of the fat-free body in the SCI population relative to age, sex, physical activity level, level of the spinal cord lesion and time post injury, and to develop equations based on multicomponent body composition models.