A cohort study in the nutrition unit at Toulouse University Hospital shows that 3 months and 1 year after surgery, there are 2 phenotypes of patients. The first one is called 'little loss' and is defined by a contribution of muscular weight lower than 15% of the total weight loss. The other one is called 'big loss' and is defined by a contribution of muscular weight higher than 15% of the total weight loss. Causes of these different phenotypes are unknown for the moment. Nothing distinguishes them before the surgery. Type of surgery, gender, protein intake (in grams of proteins intake per day) do not appear to have a determining influence about the intensity of muscle mass loss. The only other study published shows changes in muscular mass about 15% at 6 weeks.