This study investigated the change in body composition in 36 cancer outpatients receiving radiotherapy to the head and neck area (mean age: 63 +/- 15 years) randomised to receive either nutrition intervention (NI; n=15) or usual care (UC; n=21). Body weight and composition were measured at the commencement of radiotherapy and 3 months later. The UC group lost significantly more weight; mean decrease = 4.3 kg, than the NI group: mean decrease = 1.1 kg (t((30))=-2.5, p=0.019). Fat-free mass loss was significantly higher in the UC group with a mean loss of 2.2 kg versus 0.3 kg in the NI group (t((30))=- 2.3, p=0.029). Body composition as measured by foot-to-foot bioelectrical impedance analysis provides more information than weight alone and can allow for tailoring of NI.