Today still only 50% of newly diagnosed cancers can be cured. While molecular mechanisms of cell proliferation are being studied intensively, comparably little research energy, however, has been spent on unravelling metabolic interactions of cancer and host tissues. Evidence is accumulating that systemic as well as local metabolic patterns have considerable impact on tumour growth, as well as on body composition and organ functions. This may lead to new treatments in oncology. Cancer development - and recurrence - may be inhibited by physical activity, as well as by avoiding obesity, the metabolic syndrome and insulin resistance. Antineoplastic treatments induce reductions in nutritional intake and require individually tailored nutritional support. New concepts are being considered to metabolically starve or reprogram cancer cells. During palliative treatment of progressive tumours, it should be good clinical practice to avoid or treat malnutrition and chronic inflammatory states. At late stages, the primary goal should be symptomatic relief and attention to subjective individual needs.