In this article, the authors discuss obesity and the differences in the eating behaviors between Americans and French people. In the last decade or so, a number of psychologists, nutritionists, and physiologists have come to the conclusion that, in the developed world, increasing obesity can be attributed primarily to the environment in which people live and eat. It is remarkable how even small environmental changes can lead to large increases in weight, as most changes occur over and over: every meal, every day, every year. According to recent figures from the World Health Organization and the U.S. Centers for Disease Control and Prevention, the French are much less fat than Americans. Eight percent of French adults qualify as obese, compared with about 31 percent of Americans. Obviously that is not because French food is unappealing. Nor can it be because French food is lower in calories. In fact, the French diet has a higher percentage of total fat and saturated fat than the American diet. One reason is that although the French spend more time eating each day than Americans do, they have fewer eating occasions. Almost all of their eating occurs at two meals--extended lunches and dinners. In addition, the French pay more attention to the experience of eating--the taste and feel of the food in their mouths--than to the consequences of eating for their arteries and waistlines, and as a result feel less ambivalence about food than Americans do. The authors believe the so-called obesity epidemic could be halted by minor changes in the eating environment. Reducing the portion sizes of food sold in supermarkets or served in restaurants by an imperceptible amount (say, a few percent) would be a good first step.