OBJECTIVE:To investigate the effect of addition of modi®ed guar gum (GG) to a low-energy semisolid meal on appetite and body weight (BW) loss. SUBJECTS: Twenty eight mainly overweight male volunteers (age, 19 ± 56 y; body mass index, 29 AE 2 kg m À2 ; BW, 89.4 AE 9.2 kg). DESIGN: Baseline of one week with self-selected diet. Three treatments of 2 weeks with a low-energy diet divided over three times a day, consisting of a semisolid meal with (SSM ) or without GG (SSM) or a solid meal (SM) with the same energy content (947 kJ) and macronutrient composition, and a dinner of the subject's own choice. Washout periods lasted 4 weeks. RESULTS: Compared to baseline values, reduction in energy intake and BW loss were similar for SSM , SSM and SM. Appetite (hunger, desire to eat or estimation of how much one could eat) was increased in SSM and in SM compared to baseline, but not in SSM . Satiety and fullness in SSM , SSM and SM were similar to baseline. Any intervention was more effective on BW loss when it took place the ®rst time compared to the second and third times (2.6 AE 0.2 kg, 1.7 AE 0.2 kg and 1.1 AE 0.2 kg, respectively; P`0.001). The SM ± SSM ± SSM sequence was more effective on BW loss compared to the SSM ± SSM ± SM sequence (5.6 AE 1.0 and 2.5 AE 0.6 kg, respectively; P`0.05). CONCLUSION: All the three treatments were equally effective with respect to BW loss. GG addition to a semisolid meal prevented an increase in appetite, hunger and desire to eat, which increase was present in the other treatments. However, differences between treatments were not statistically signi®cant. The order effect shows that repeated 2-week bouts of dieting become increasingly ineffective. The sequence SM ± SSM ± SSM was more effective than the sequence SSM ± SSM ± SM, probably because compliance was relatively higher with the SSM or SSM diet, and compliance decreased towards the end of the complete experiment.