Are large portions responsible for the obesity epidemic?

Large portion sizes are frequently blamed for the obesity epidemic. In this paper, we examine the culpability of large portion sizes. It is true that portion sizes have increased during the obesity epidemic, but there is as yet little evidence that exposure to large portions produces significant weight gain. Furthermore, some evidence argues against the role of large portions in the obesity epidemic. For instance, the epidemic is largely a matter of weight gain among the upper half of the population weight distribution, whereas large portions appear to have an indiscriminate effect on food intake. Factors other than the size of individual meals may well be responsible for a great deal of the observed population weight gain.