Some people with cancer suffer from muscle wasting, lose weight and feel tired. This process, termed cachexia, is a significant problem and can lead to a reduction in both quality and quantity of life. Cachexia is caused by interactions between the tumour and the patient. Historically, it was considered to be a purely end-stage phenomenon of advanced cancer, however, it is now known that early signs of cachexia can even influence the outcomes of patients with potentially curative pathology, including those planned for a surgical resection. This study aims to collect information, from patients who are at risk of cachexia, about body composition, physical activity, quality of life and the body's immune response to cancer. Previously these measures have been most frequently studied in isolation, or at one single time-point, and are therefore likely to give an incomplete picture. A more holistic characterisation of surgical patients at risk of cancer cachexia, across their treatments, is currently lacking. Participants with cancer will be recruited to the study from surgical services in the United Kingdom (UK). A small number of 'control' patients without cancer, who are undergoing surgery for a benign condition, will also be recruited for comparison. Those recruited will have their height and weight measured, answer questionnaires about quality of life, undergo assessment of their physical function and levels of activity, have blood taken to analyse markers of inflammation and have their body composition measured by a variety of methods. A subgroup of patients will also undergo an additional magnetic resonance imaging (MRI) scan of their abdomen and thighs. At the time of their operation, participants will also have small biopsies of muscle, fat, tumour and urine taken for biochemical analysis. Patients with cancer, will be asked to return for three follow up appointments during the year after their operation where these assessments will be repeated.