['Although androgen deprivation therapy leads to weight gain within the first year in men with prostate cancer, longer term changes and the relationship to patient age are not well characterized. We examined long-term weight gain by age group in men on androgen deprivation therapy for up to 36 months.', 'Three cohorts matched by age and education were recruited in this prospective study, including men in whom continuous androgen deprivation therapy was initiated, controls with prostate cancer and healthy controls. All patients with prostate cancer had nonmetastatic disease. We performed age stratified (less than 65 vs 65 years or greater) comparisons. Univariate and multivariable associations with weight change with time were evaluated using linear regression.', 'We included 257 men with a mean age of 69.1 years. At baseline the cohorts were similar in age, education, body mass index, weight and comorbidity. Androgen deprivation therapy was associated with weight gain from baseline at 6, 12, 18, 24, 30 and 36 months compared to controls with prostate cancer and healthy controls (p = 0.006, 0.015, 0.028, 0.003, 0.014 and 0.0004, respectively). The proportion of men who gained weight was higher among androgen deprivation therapy users than controls with prostate cancer and healthy controls at most time points. Age stratified analyses showed that younger patients (age less than 65 years) on androgen deprivation therapy had significantly greater weight gain with time than older patients (4.7 vs 1.4 kg, p = 0.005). However, age did not appear to affect weight change with time in men not on androgen deprivation therapy (p = 0.37).'] Does impact of androgen deprivation therapy on weight gain differ by age in men with nonmetastatic prostate cancer?