We know now (although many still do not fully appreciate this) that obesity is a major risk factor for cancers. On the other hand in patients with many chronic diseases, larger patients tend to do better and live longer (the obesity survival paradox).
Last week researchers from the University of Alberta published a study in The Lancet Oncology, that adds another level of complexity to the relationship between obesity and cancer survival. Clarisse MirandaPrado together with other researchers from the UofA, including cancer cachexia researchers Vickie Baracos, studied 2115 patients with solid tumours of the respiratory or gastrointestinal tract, 325 (15%) of who were classified as obese (body-mass index [BMI] >/=30).
With the help of CT images, the researchers found that obese patients had a wide range of muscle mass, with 15% of analysed obese patients meeting criteria for “sarcopenic” obesity (sarcopenia is the medical term for low-muscle mass). By definition, sarcopenic obese patients have more body fat and less lean body mass than non-sarcopenic patients of similar weight.
Not only was sarcopenic obesity associated with poorer functional status compared with non-sarcopenic obese patients but these patients also had a 4-fold hgher risk of dying.
Incidentally, the researchers also used their data to calculate that using conventional dosing criteria for cytotoxic chemotherapeutic drugs, sarcopenic obese patients may be overdosed with a greater likelihood of toxicity.
Overall this study shows that obesity is never just obesity and that BMI in the clinic is a fairly useless concept (a point that I have argued before) and that without proper assessments of body composition rational management of large patients is just not possible.
A patient’s size alone proves little in term of health or disease – remember, weight alone is a rather poor measure of health.