Dexfenfluramine has been demonstrated to produce decreases in daily energy intake varying between 13 and 25% depending on the time for which the drug has been administered. This reduction in energy intake is achieved by a decrease in the size of meals (11-40% depending on the dose) and by a decrease in the frequency of snacks consumed between meals. These objective adjustments are accompanied by a decrease in the level of perceived hunger, particularly apparent in the postprandial period. Taken together these changes can be interpreted as an action of dexfenfluramine to intensify the satiating power of food. This effect is consistent with the proposed role of serotonin systems in the mediation of satiety. The effect of dexfenfluramine on eating parameters leads to an overall modulation of the pattern of eating and the profile of motivation to eat. The reduction in energy intake achieved by this modulation is consistent with the weight losses recorded following several months of treatment. This restraint over the expression of appetite exerted by dexfenfluramine appears to be present even after 12 months of continuous treatment. These demonstrated actions should help overweight people to achieve a better management of their appetite in order to assist weight loss and to prevent weight regain.