Obesity is an epidemic in the United States. In 2009, there were only three states with less than one in five people considered obese, or having a body mass index (BMI) of less than 30. The effects of this issue on our health system and society at large are well documented, yet there is another population worth examining. Obesity poses numerous specific risks and problems for those with spinal cord injury (SCI). With greater awareness of the issues we can anticipate and manage challenges that may easily go unrecognized using standard measures of obesity.
To start with, the standard BMI measurements are not accurate in this population. The test lacks the specificity to differentiate body fat from fat-free lean mass. In addition, a tetraplegic SCI patient who has a measured BMI of 25 kg/m2 may have a body fat percentage in excess of 35% (standard for men is 22%). Adipose, or fat cells, produce a variety of proinflammatory proteins known as cytokines, including interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha). Excessive adipose tissue (fat) is known to produce these cytokines which have been implicated in cardiovascular inflammation, hyperlipidemia, insulin resistance, hypertension and thromboemboli.
The energy balance that contributes to increased obesity is profoundly affected in patients with SCI. Injury to the somatic nervous system results in loss of stimulation to skeletal muscles below the level of injury, and thus loss of metabolic activity. Therefore, predicted energy expenditures in SCI patients are overestimated by approximately 25% when compared with non-SCI persons. Overfeeding, therefore, results in increased obesity and the numerous sequelae. A US Department of Veterans Affairs study of SCI patients estimated that at least half of the individuals who had normal BMI by standard measures would be classified as obese by body fat percentage.
Why does this matter so much in SCI injured patients? Obesity puts these patients at increased risk for metabolic syndrome and a host of cardiovascular complications. In addition, it places increased stress on the joints of the upper extremity because of greater strain in carrying weight, as well as the lower extremity because of the abnormal joint forces associated with spasticity, reduced proprioception and neurogenic gait dynamics.
Physical therapists working with SCI patients should be aware of these challenges. Not only will supporting activity and mobility with appropriate devices provide necessary physical activity, but also it will prevent pressure ulcers. As we know, the development of pressure ulcers can have a devastating effect on this population.
It is important to recognize that SCI patients present with unusually high risk for the complications of obesity, and the diagnosis may go unrecognized by standard measures of obesity. Any therapeutic plan for SCI patients should include careful attention to nutrition to foster a healthy lifestyle and reduce the chances of obesity and its complications.