Stavropoulos–Kalinoglou A et al. – Inflammation does not seem to influence BMI and body fat (BF) in RA. As in the general population, high levels of habitual physical activity associate with low BMI and BF in RA. Energy intake is a major determinant of being underweight in those who consume fewer calories. Further research is needed to investigate the suitability of exercise and diet modalities, and their effects on the body composition of RA patients.
http://www.nature.com/ijo/journal/vaop/ncurrent/abs/ijo2009220a.html