Diets higher in protein content result in increased satiety and energy expenditure. In the short term, gelatin showed stronger hunger suppression and less subsequent energy intake compared with other proteins. The present study investigated whether a supra-sustained gelatin-milk protein (GMP) diet promotes weight loss compared with a sustained milk protein (SMP) diet and a supra-sustained milk protein (SSMP) diet during an 8-week diet period. A total of seventy-two healthy subjects (312 (sd 48)kg/m2; 43 (sd 10) years) followed one of the three diets in a subject-specific amount: SMP, SSMP or GMP diet. During weeks 1-4, energy intake was 100% of individual energy requirement: 10, 40 and 50% of energy (En%) as protein, fat and carbohydrate, respectively (SMP diet), and 20, 30 and 50En% as protein, fat and carbohydrate, respectively (SSMP diet or GMP diet). During weeks 5-8, energy intake was 33% of individual energy requirement: 30, 35 and 35En% as protein, fat and carbohydrate, respectively (SMP diet), and 60, 5 and 35En% as protein, fat and carbohydrate, respectively (SSMP diet or GMP diet). Thus, absolute protein intake was kept constant throughout per subject. Significant decreases in BMI (P<00001) were similar between the GMP (17 (sd 05)kg/m2) and the SMP (21 (sd 08)kg/m2) and SSMP (16 (sd 05)kg/m2) diets. Decreases in fat-free mass (FFM), fat mass (FM) and FM%, and increases in FFM% were similar between the GMP and both control diets. Changes in RQ differed (P<005) between the GMP (001 (sd 006)) and SSMP (004 (sd 004)) diets. Changes in HDL concentrations differed (P<005) between the GMP (021 (sd 018)mmol/l) and the SMP and SSMP diets (008 (sd 018)mmol/l and 009 (sd 026)mmol/l, respectively). In conclusion, a gelatin-milk protein diet does not induce more beneficial effects during an 8-week weight-loss period compared with a SMP or SSMP diet.