BACKGROUND & AIMS: Although changes in weight have been reported after traumatic brain injury (TBI), their frequency and underlying factors are little known. Our aim was to determine the prevalence of weight changes and the associated factors during the recovery phase after TBI. METHODS: Longitudinal follow-up of adults with TBI. Multivariate analysis was carried out on weight change, demographic data, dysexecutive syndrome, eating behavior, physical activity, therapeutic classes and metabolic complications. RESULTS: 107 patients (81 males/26 females), age 36 ± 13 yrs, baseline BMI 23.3 ± 3.9, followed for 38 (8-66) months, were included. In intensive care, patients lost a mean 11 ± 6 kg. End of follow-up, mean BMI was not different to pre-TBI BMI, but patients could be categorized in 3 groups: stable (30%), loss (28%, -8 ± 7 kg) and gain (42%, +9 ± 6 kg). Sex, age, severity of TBI, intensive care weight loss, physical activity, therapeutic classes and the occurrence of metabolic syndrome did not differ between the groups. Factors related to weight gain were hyperphagia, OR 4.5 (IC95%, 1.6-12.1) and presence of a dysexecutive syndrome, OR 2.5 (IC95%, 1.03-6.3). Factors related to weight loss were hypophagia, OR 4.1 (IC95%, 1.5-10.9) and higher pre-TBI BMI, OR 4.9 (IC95%, 1.7-14.0). CONCLUSIONS: Over a median period of 38 months, 42% of TBI patients gained and 28% lost weight. Factors associated with these changes were the presence of a behavioral dysexecutive syndrome for weight gain, oral food intake and initial BMI, which were inversely associated with weight at end of follow-up. These findings highlight the importance of evaluating the time course of weight changes and providing specific nutritional care.