The link between obesity and increased risk of mortality is well established. However, those who are obese have greater survival when they have chronic diseases such as rheumatoid arthritis or cardiac failure; this is known as the "obesity paradox". The obesity paradox is most probably attributable to obese individuals being more susceptible to milder forms of disease than normal-weight individuals, although other mechanisms may also operate. The benefits of weight loss in the general population are also unclear, as some study participants also lose weight through disease. Further work is required to help guide weight recommendations in both healthy individuals and those with chronic diseases.