The fat-trapping capacity of a chitosan product was studied in 24 volunteers who were instructed to follow customised diet plans (five meals/day for 12 days). Oral charcoal markers defined two 4-day experimental periods. Two capsules were taken five times per day before each meal during the supplement period (2.5 g chitosan/day) and not during the control period. Feces were collected from day 2 to day 12. Feces from each period were pooled and analysed for fat content. For men the average daily intake was 137 ± 31 g fat and 3256 ± 624 kcal. For women it was 89 ± 16 g fat and 2110 ± 195 kcal. Each two-capsule dose was consumed with 28 ± 11 g fat in males and 18 ± 7 g in females. Fecal fat excretion increased with chitosan by 1.8 ± 2.4 g/day in males and did not increase with chitosan in females.