Part 2: Limitations surrounding use of current BMI measurements and their impact in litigation.
In Part 1 of this series, we discussed the origin of Body Mass Index (BMI) and how a quotient developed in the mid-1800s to determine the “ideal” body size has persisted into present day medicine despite its proven faults. In Part 2, we will discuss more of the limitations of BMI in current medicine as well as some of the associated medical risks and disease states associated with obesity.
BMI can indicate the relative amount of body fat on an individual’s frame but does not directly calculate body fat percentage. BMI tends to overestimate body fat in those with a lean body mass (eg, athletes or bodybuilders) and underestimates excess body fat in those with an increased body mass. Take for example, basketball player Michael Jordan. When he was in his prime in the late 1980s to early 1990s, his BMI was 27-29, classifying him as overweight, yet his waist size was less than 30 inches. As discussed, BMI does not measure body fat directly, but BMI is moderately correlated with more direct measures of body fat obtained from skinfold thickness measurements, bioelectrical impedance, underwater weighing, dual energy x-ray absorptiometry (DXA) and other methods. Furthermore, BMI appears to be strongly correlated with various adverse health outcomes consistent with these more direct measures of body fatness according to the Centers for Disease Control and Prevention (CDC).
In the United States, the prevalence of overweight and obese individuals has risen dramatically over the last 25 years, with more than half of all adults in the U.S. now considered to be overweight or obese. It is well-established that elevated BMI can contribute to several cardio-metabolic conditions, including diabetes, hypertension, and coronary artery disease, which are among the leading causes of premature death in the U.S. Individuals with abdominal obesity are at a greater risk of acquiring multiple pathological conditions and have a higher morbidity and mortality rate. However, BMI has no way to account for this variable.
Various studies throughout the years have shown that individuals with a BMI >30kg/m2 are at increased risk for the development of:
- Heart disease, high blood pressure and stroke
- Diabetes; people affected by obesity are about 6 times more likely to have high blood sugar
- Some cancers; colon, breast (after menopause), endometrium, kidney, and esophagus are linked to obesity;
- Osteoarthritis; most often affects the knee, hip, or back. Carrying extra pounds places extra pressure on these joints and wears away the cartilage (tissue cushioning the joints) that normally protects them.
- Gout; related to insulin resistance and excess uric acid crystals that get deposited in the joints
- Obstructive sleep apnea; more than half of those affected by obesity have OSA
What does this all mean for your legal case? There is a vast amount of information available to support the association between obesity, or a BMI >30 kg/m2, and a wide range of medical complications. If you are working on behalf of the plaintiff and they fall into the obesity range of BMI or greater, then any of the medical issues listed above could be used as mitigating factors against your client if present prior to the incident. In addition, there are injury-specific risks associated with obesity that can be damaging to a legal case including:
- Obesity is associated with an increased risk of back pain. Excess weight also tends to prolong the recovery period after episodes of back pain. Persons who are obese and/or have a high percentage of body fat are 33% more likely to experience low back pain and 35% more likely to experience severe, intense pain, and for women, about 100% more likely to experience disability and functional limitations. Obese or overweight patients are considered more likely to experience a herniated disc, a common cause of leg pain or sciatica due to a lumbar radiculopathy. The disc is more likely to herniate as it is forced to compensate for the pressure of extra weight on the back. Extra body weight strains joints in the spine and leads to an increased risk of developing spinal osteoarthritis. A BMI greater than 25 increases the risk of developing osteoarthritis. 
- Obese patients have an increased risk for falls and fall-related injury, not just because of the loads involved, but also because of the strategies they use to recover from a trip or slip. Research indicates that obesity does not appear to cause more frequent slips or trips, but it does negatively affect the ability to recover balance and prevent a fall compared with normal-weight people. One particular study found the higher rate of obese-adult falls may have resulted from factors that contribute to trunk kinematics, the features or properties of motion in an object. These include an anterior shift of the trunk center of mass among obese adults, which could increase the gravitational movement that rotates the body forward after tripping; greater trip mass, which increases trunk momentum; and relatively low trunk and lower extremity strength, which could reduce the ability to slow trunk momentum.
- Obesity has been associated with fatty degeneration of the rotator cuff, even in the absence of a rotator cuff tear, and therefore is thought to potentially be a risk factor for rotator cuff repair non-healing.
- In obese individuals, there is extra pressure put on the knee joints to support that weight. The extra pressure on the knee joints affects the cartilage in the knees. This can cause the cartilage in the knees to thin or wear out quicker. Less cartilage means poorer cushioning, which could lead to numerous knee problems and conditions.
- Obese patients have a 25% increased risk of workplace injury.
- Overweight and specifically obesity with BMI above 30 doubles the probability for hernia, and the prevalence of hernia symptoms in patients with morbid obesity reaches 50%. Obese individuals have an increased amount of visceral fat in the midline which increases intragastric pressure.
- The odds of sustaining an injury were found to be 15% to 48% higher in overweight and obese individuals than in normal-weight patients, and hospital mortality rates following trauma were reported to be 7.1 times higher in obese than in non-obese patients.
- Patients with obesity have been observed to have particular patterns of injury. For example, obese patients have had fewer head injuries, but more chest and lower extremity injuries, and a study involving patients in head-on motor vehicle collisions (MVC) showed that obesity was associated with higher risks of lower and upper extremity injuries, as well as spinal injuries.
In Part 3, the final piece of this series, we will discuss the most recent studies published on BMI and how that research is changing the way healthcare professionals and the rest of the word look at the “ideal” body type.