The purpose of this study was to examine the relationships of gender, age, usual weight, and tobacco use with cancer-related weight loss, food intake, and resting energy expenditure. Data were collected from medical records, interviews, self-report diet records, indirect calorimetry, and 40K counting. A convenience sample consisted of 60 subjects with non-small cell lung cancer who were at least one month postradiotherapy. Mean weight loss was 2 kg at diagnosis and 6 kg at six weeks postradiotherapy. Partial correlations, controlling for stage of disease, indicated that gender, age, and current smoking correlate significantly with cancer-related weight loss and decreased food intake. Gender, age, and current smoking accounted for 21% of the variance of weight loss postradiotherapy over and above stage of disease. Potential practice implications focus on enhanced nutritional assessment and early intervention for men, the elderly, and current smokers, who are at higher risk for weight loss.