It is still uncertain whether subgroups of obese subjects demonstrate different eating patterns. The aim of this report is to compare data on dietary intake obtained by different methods (dietary history and dietary diary) in several groups of obese patients in which the effects of weight-reducing agents were investigated. In our first and our second study, the latter part of an international multicenter study, we investigated the weight-reducing potential of lipase inhibition, a novel concept in the treatment of obesity, in healthy moderately obese subjects. In the third study, part of a national multicenter study, we investigated the effect of a serotoninergic drug (dexfenfluramine) on eating habits in moderately obese people who considered themselves snackers. Eating habits of the third group seem to be different from those of the other two groups in both men and women. These patients have a greater total energy intake due to a greater carbohydrate and fat intake. In our second study, little difference is found when results obtained by dietary history are compared with those obtained by dietary diaries. Our comparisons indicate that groups of obese patients with different patterns of eating behavior may exist and that obese snackers have a significantly greater energy intake. Therefore, various therapeutic strategies for weight reduction may be useful for patients with different types of eating behaviors. Furthermore, the methods by which data on dietary intake are obtained seem to show comparable results and therefore at least suggest accuracy. © 1995.