Effects of anorexic drugs on food intake, food selection, hunger motivation and subjuctive experiences

Two anorexic drugs with contrasting neurochemical profiles—amphetamine and fenfluramine—have been incorporated into the experimental technique of double dissociation to explore relationships between certain features of feeding behaviour and subjective experiences surrounding eating. In general, the drugs brought about opposing effects on behaviour and subjective states. A test meal revealed that amphetamine gave rise to a marked suppression of protein consumption whereas fenfluramine exerted a greater suppression on carbohydrate intake. Similar directional effects were observed on a food preference questionnaire, and it is noted that subjective preferences were a more sensitive indicator of the presence of an active drug than actual behaviour. The drug treatments exerted quite different effects on ratings of hunger, various subjective feelings and bodily sensations. Amphetamine brought about prominent effects on the appetitive phase of eating, whereas fenfluramine appeared to enhance or prolong the post-prandial state. The strength of the correlation between hunger and eating varied markedly between the conditions. Taken together these findings are in good agreement with the results of research on animals and they suggest that certain drugs may be useful as tools to explore processes influencing feeding activities.