There is evidence to support that mastication may contribute to the prevention of weight gain via reduction of appetite sensations and subsequent energy intake. However, the metabolic effect of mastication after consumption of a daily meal, composed of the staple food (rice), soup, main and side dishes, is limited. Therefore, the effect of thorough mastication on greater satiety and the thermic effect of a meal (TEM) was investigated in young women. In study 1, energy expenditure (EE) derived from masticatory muscle activity for 20 min was measured while chewing hard, tasteless, non-caloric gum in seven subjects. In study 2, ten subjects consumed a solid meal performing 30 chews per mouthful (30 CPM), or swallowed the same, pureed meal without chewing (0 CPM) on two separate days, and postprandial EE, substrate oxidation, subjective appetite ratings and autonomic nervous system (ANS) activity for 3 h were examined. Both test meals were iso-caloric (2,510 kJ) and-weighted (884 g), and consumed in 20 min. From study 1, the EE of mastication itself for the 20 min was estimated to be 3.7 +/- 0.8 kJ. From study 2, significantly higher TEM (134.2 +/- 15.5 vs. 67.8 +/- 13.8 kJ/3 h, p<0.001) as well as satiety (p=0.005), and tendency toward greater fat oxidation (p=0.090) and ANS activity (p=0.069) were observed after consumption of the meal with 30 CPM compared to 0 CPM. In conclusion, thorough mastication before swallowing increased postprandial satiety and the TEM in young women, suggesting such eating behavior may be useful for preventing obesity.