Researchers in the UK have discovered that individuals with rheumatoid arthritis that have a “normal” body mass index (BMI) may actually have more fat in their bodies than those who do not have the disease. The team collected data from 174 RA patients, 43 osteoarthritis patients and 82 healthy patients. They found that the RA patients had a lower BMI than the healthy patients with the same body fat content. This enabled them to determine that the normal BMI range of 18.5 to 24.9 should be reduced by 2 for people with RA. This leads to a normal BMI of 23 for rheumatoid arthritis patients. Since higher body fat can increase the risk of cardiovascular disease people with RA may want to reconsider what their healthy weight should be.
Body mass index was invented between 1830 and 1850 by Adolphe Quetelet. It is the ratio of height to weight that is commonly used to classify people as underweight (less than 18.5), normal weight, overweight (25.0 – 29.9) or obese (over30). BMI is calculated by the following formula: